Minx upgrade.

[RBT]

I have a "restored" minx with a 350 mpi and bravo drive. I bought it off this board a few years ago and while I like the boat it is a bit of a turd.
Best speed form it so far is 59.2 mph.
So if all goes to plan in the next few weeks, I am trading a friend my 350 mpi for his 502 mpi and my stock bravo lower for his -2 imco lower ( plus some cash)

Anyone have any idea on how much faster it might be?
also while I am at it I am considering adding stainless marine exhaust, thoughts?

RT

[Morgan's Cloud]

IMHO I think that would be a tad a$$ heavy . Plus the 502 , I think , is a bit much for the boat's construction.
A built 350 or 383 would be a better way to go I think .

[Greg Guimond]

Is there room for a Blower? Might get you close to a 415hp 502MPI given you will gain back a little over 1mph for each 100lbs of weight you avoid. Just a thought.

[gcarter]

My Minx w/a pretty stock 350 Vortec would do 65 on a good day.
I really don't recommend a BBC in a Minx. The engine compartment is about 6"-7" shorter than a 22C engine compartment, and the hatch size is about the same as an 18C (the engine comes out sideways).
My recommendation would be a pretty warm SBC w/about 400-425 HP and an Alpha.
I believe this package would be good for 70-72 MPH.
Understand, no one here has ever seen an 80 MPH Minx, so keep your expectations in reason.
I think the extra weight of a BBC in the Minx would not be a step in the right direction.

[RBT]

The boat already has a bravo, so there is no going back to an alpha. My old 18 had a 400 with an alpha ss, I am not a fan of small blocks.

Years ago, hot knots in orillia ontario did an all red minx, called "red hot", it had a bravo and a 454 mag, 365hp. If memory serves it ran a 27 mirage prop to close to 5000 rpm. Math suggests it is or was close to if not better than 70. I was young but remember it being a fine ride, but it did chine walk and the owner couldn't drive it.
My opinion is that a 454/502 with light exhaust isn't much different in weight than a stock 350.
As for a minx over 80, in time I hope to be. I am just major league limited on time. My long term goal it to do a real resto-mod on the boat, core the hull blueprint the bottom, a reall stringer system and re-gel it. Then rig it to the hilt, I am major anal about my stuff and this boat in its current state is embarrassing.
Oh and my sea ray runs 84, it doesn't seem right that the donzi is following it.

[biggiefl]

Screw the Minx...show us the 84mph SeaPig!

[RBT]

Pachanga 22, 511 CID, based on 502. Makes 570 ish hp on active engines dyno, 1:36 gears lab bravo 26 at 5800 rpm. Imco drive, steering and exhaust, would be faster if I removed the stock vernalift mufflers. They really snuffed the motor but it sounds almost stock. The only givaway is the oil temp, water psi and fuel psi gauges
It is a fun boat

[joseph m. hahnl]

Only one way to find out :D .No Guts No Glory:salute: I'd say do it Bro!



Jeff's Boat:worthy:


https://sphotos-a-lga.xx.fbcdn.net/hphotos-prn1/1012061_411304808982405_550460754_n.jpg

[Greg Guimond]

The boat already has a Bravo. As for a Minx over 80, in time I hope to be.

It sounds like you are looking to build the fastest Minx.

[RBT]

Fastest, that never really crossed my mind but for reference what is the target?

how does the Arneson powered boat run?

[gcarter]

Your structure plans are the correct direction as the hull was never intended for more than about 350 HP. They all have hooks on both sides of the hull....except for my old Minx, and Jeff's Minx, they've both been fixed (there's a thread on here somewhere of removing my hooks).
I also beefed up the stringers in mine, but not for 500 HP.
But why you even bothered to ask the question of upgrading to a BBC, I was puzzled. You've obviously already made up your mind since you received three negative responses.
I thought Greg's response was on the correct track as there's loads of vertical room under the hatch.

I wish you well.

[RBT]

Yes I have made up my mind, I was more interested in what you all figure the speed increase might be.
As for the hook, it is horrible. I can see it..... Passenger side is worse.

My loose plan is to remove the deck. Remove the structure, vacuum bag in a balsa core, replace the stringers. Then flip it over and blueprint the bottom.
I am going to add a full transom as well, as I want to add k planes and real steering. For now, the motor and lower as it is easy.

[Greg Guimond]

What are you planning to do about the CG ?

[mattyboy]

nice shot of jeff's boat running

so the Minx is not a 2 foot shorter 22 it is a 4 foot longer skisporter. I was surprised to see the short inner strakes on a production boat from the mid 1980's when the classics they were making at the time had longer inner strakes. I am far from nautical engineer but i would imagine that is why you don't see alot of fast minx's just like the skisporter they require a lot of power and the right setup to run above 65. wonder if that was done for a softer ride of a rounded keel with no lift and speed was sacrificed??

good luck on your project

[gcarter]

I've pondered many times why the Minx doesn't seem to respond well. In so many ways it's similar to a Cig 20, but the hull is a totally different critter. Also, the Minx has quite a lot of frontal area to contend with. As speed increases, the parasite water drag decreases as the hull lifts out of the water and wetted surface decreases, but air resistance increases w/the qube of the speed.

[mattyboy]

I've pondered many times why the Minx doesn't seem to respond well. In so many ways it's similar to a Cig 20, but the hull is a totally different critter. Also, the Minx has quite a lot of frontal area to contend with. As speed increases, the parasite water drag decreases as the hull lifts out of the water and wetted surface decreases, but air resistance increases w/the square of the speed.

George that was part of my point the minx hull with the short lifting strakes doesn't have as much lift as the 18 or the 22 so it will have more wetted surface. Same for the early skisporter and the 18 both with identical power and drive the 18 will be faster more lift less wetted surface

[smidgen too]

Only one way to find out :D .No Guts No Glory:salute: I'd say do it Bro!



Jeff's Boat:worthy:


https://sphotos-a-lga.xx.fbcdn.net/hphotos-prn1/1012061_411304808982405_550460754_n.jpg

Before you make power upgrades to a Minx make a complete check off your hulls integrity. Just remember Jeff's Minx has had a deck off Restoration, bow water ballast tank & new transom & stringers that are actually glassed to the hull, not like the factory. Jeff's Minx ROCKS we had it out out on Lake St Clair in a nasty chop & it was great !!!!

[gcarter]

As familiar as I was w/the Minx, I think you saw something I never did.
Here's some pictures of the Minx on dollies (before I had removed the hooks), and the Testa Rossa (22C) while it was upside down and I was gelling it. There's a huge difference as to the inner strake termination.
This is probably why the Minx makes such a fine cruiser and a lousy speed boat.

http://www.donzi.net/forums/attachment.php?attachmentid=43770&d=1236022763

[Greg Guimond]

As a guy who has spent a lot of foolish money making a slow Donzi go fast, I'm not sure I would go any further with that hull than a blower. I'm just wondering what the landing re-entry might be like with a BBC's weight. Is anyone running a Minx with a 502 currently on the board? There are folks here who will know the exact weight differences between what you have + a blower -vs- a BBC. As far as the glass work needed RBT has the access. How fast does that Arneson Minx go roughly? It might make more sense just to buy Parnell's fully sorted boat.

[silverghost]

I tend to agree with George, Greg, and others on the Minx hull.

Rather than the BB Chevy & the shorty you mght be better with a SB 383 or 400 Chevy and an Arneson drive to get the sort of speed you are seeking.

The Minx's short inner bottom strakes & hull hook shape was never designed for fast speed~~~You would have to totally re-design it's bottom ~~~and in the end, after all this work and money, might not get your expected results.
I suspect Donzi never intended the Minx to be a very fast hull~~~It's more of a family style speedboat.

Why not look out for a Donzi "Classic Style " 22, 18 or Blackhawk hull project with a Mercruiser Blackhawk surface drive ~~~then the speeds your are looking to achieve would be very realistic ?

There is/was a cheap partially stripped Donzi Blackhawk 22 hull for sale in MD that mike make a better project boat for this sort of 70-80 MPH speed.

I also~~~have become addicted to throwing lots of time and cash into these sorts of crazy speedboat projects.

I too~~~ would like to see photos of that 84 MPH Sea Ray !

[Just Say N20]

There is NO doubt that buying either of Parnell's boats (the 16 and GT21 are both for sale last I knew) would put you way ahead in every area, including what you would end up spending. And you would get a known commodity.

[gcarter]

To be fair to RBT, there are "some" BBC (454) powered Minx's.
Dale Evans in Miami has one, it's a transplant (not original) and runs in the low 70's I understand.
Donzi had a 330 HP BBC on at least one price list I've seen, but I'm not aware of any being built.

[mattyboy]

George and RBT I would be interested to know if the hook is intentional or was it due to strorage methods , age and construction flaws and where exactly it is on the bottom.

George you are correct the early cig 19-20 hulls are very much like the minx or vice versa since the cig came first. the bottoms changed on the cig as it progressed thru it's lifetime.

I'll see if I can dig up some pics of the cig 19 hull during that project .

I know the short straked round bottom early Walters' designs the 16 and 19 have intentional hook outward of the outer strake in the chine area would be nice to know if that was incorporated into the Minx design

RBT

If you are looking for all out speed your hull might not be best and the advice given is accurate. My take would be if you want a boat that will handle chop fairly well and give you an in the boat feeling that is fairly rare and uncommon that will perform in the 65-70mph without major mods the Minx fits that bill very well.

judging by the pics Jeff has the wetted surface thingy all figured out nice boat !

[gcarter]

Matty, there was nothing planned about the Minx hooks. They're long (4'), narrow (18"), upside down "bowls" and vary from side to side.
It's entirely a mold/timing issue (I believe so anyway) and has nothing in common w/the 16 hooks.

[Greg Guimond]

Actually I had a second cup of coffee and now feel that RBT would be out of his mind to embark on a restoration and power upgrade of the magnitude he is considering when he could just sell the Minx for $10,000 and then buy Parnell's GT-21 for $50,000. Parnell would meet you halfway so no shipping to pay for either.

What am I missing here? This is actually more than a no brainer, it is a gift. The GT-21 ad detail below with the big dollar items highlighted by me.


I am putting my GT-21 up for sale. It's a 1976 which has undergone a complete 2 Year restoration well documented with pics on this thread
Completely New Gel Coat, New Mitcher T Paint job
New Transom, Installed 3 full bulkheads and numerous gussets and supports
New Custom 102 gallon fuel tank foamed and glassed in. Custom glassed in floor lowered 3"s
New Livorsi Gauges including GPS Speedo, Depth Finder, Fuel Flo Scan Gauge and Knock Meter
New Sony Stereo with remote JL Speakers and 4 Channel JL Marine Amp
New Livorsi Throttle with Trim and Shifter in custom Center Counsel, New Stainless Marine Vertical Trim Indicators
New Interior with 5 Custom Skater Seats with Storage under and alongside, New Top, New Cockpit Carpet
Big Block Engine (Fresh 10 Hours) with Stelling Headers and custom tail pipes exiting under water
HP, Speed, Complete Engine Build List and Dyno Sheet available for serious inquiries
New Dual Axel Integrity Trailer with Spare and Brakes
Bravo XR with all new gears on Mercury ITS Transom Assembly with Built in Hydraulic Steering
2 SS Props and 2 Gel Batteries with Offshore brackets plus Garmin 4205 GPS
380 S K-Tabs with Race Hydraulic Cylinders
Fresh Water Flush, All lines on Engine are Braided. Stainless Steel Rub rail. Custom Engine Hatch

This boat is exceptionally stable at high speeds and is rock solid in snotty conditions High freeboard offers very dry ride in waves. Boat is very solid and is running perfectly. Sea trial available for serious inquiries. delivery available most places Call to Discuss - Parnell 616-437-3852

[mattyboy]

Matty, there was nothing planned about the Minx hooks. They're long (4'), narrow (18"), upside down "bowls" and vary from side to side.
It's entirely a mold/timing issue (I believe so anyway) and has nothing in common w/the 16 hooks.


Thanks George

the hook on the hornet is different from the hook on the 16 the outer strake tapers into and the disappears into the hook on the 19, on the 16 the outer strake stays the same all the way back.

[olredalert]

----Im almost positive that Jeff has blueprinted his hull and removed any hook. Other below-the-surface mods also may have been performed, but I cant remember what. Mark will know and Jeff may chime in. I believe Jeff may be overseas at the moment........Bill S

[mattyboy]

George,

I think the Minx was designed to replace the Hornet the last Hornet III rolled off the line in 86 , the minx was from 85-88 ish. More of a Couple's boat higher freeboard more secure feeling than the 18 and 22 classic more of a town car than a pony car. This is an interesting time in Donzi history The Staples era, the family and bigger performance boats came along , the classic line was only the 18 22 and Minx . the family performance boat was the z21 and then the 25 and 29 footers with the flare and styling. Then in 88 the OMC era when they regurgitated other OMC companies styling cues into the family runabouts and cruisers.

[gcarter]

Bill, I know Jeff removed his hooks because he asked me questions about mine and sent me pictures of his progress.
I'm not aware of any other modifications to his hull bottom, but it's a very nice boat w/his Arneson install.

[smidgen too]

----Im almost positive that Jeff has blueprinted his hull and removed any hook. Other below-the-surface mods also may have been performed, but I cant remember what. Mark will know and Jeff may chime in. I believe Jeff may be overseas at the moment........Bill S

Bill , Jeff did blueprint the bottom & re gel coated it. Jeff is back but leaves again this weekend. When we were out in his Minx he ran it like he was in his 27' Magnum. :embarasse What a difference two feet make in the ride of the Minx compared to our X-18.

[RBT]

I am no stranger to doing stupid things, I have over 100k in a carbon fiber Stv.
As for all the glass work that is easy, I have build more than my fair share of boats, carbon Kevlar and advanced composites are my specialty. Adding strakes to the bottom is a walk in the park.
As for the hook, there is no way it was planned, it is very visable. One thing people forget is that when the boat is built it shrinks in the mold. Big flat surfaces tend to hook. Edges are better at retaining shape.
My intention for the big block, specifically the 502 mpi is it is free. I was also considering the weight, if memory serves the big block was only 100 lbs or so more than a 350. Remove 65-70 lbs for stainless marine exhaust and it is close. While a built 377-383 or 400 could or should have aluminum heads, the same can be said of the big block should I ever get into it. Adding a blower will make it weigh similar to the 502.
I can also move weight, example there is no reason I can't move the battery up.
For now, I will likely just throw the motor in and the shorty lower and see what happens. Cost to me is about a days labor. The big plans for the boat are a year out.
Pictures to follow when I get home.

[CHACHI]

RBT, I had a Minx with an Alpha S/S, it was also a stock 350 MAG. NO DIFFERENCE in speed with the S/S.

That could be different with BB power.

Ken

[RBT]

On the 20 cigarette, I have a few friends with them..... Tanks!
One with a 350 with a b&m blower trs drive runs high 60's, another with a 454,330hp and a bravo runs 67 almost the same. Another with 454 mag, b&m blower and a bravo with raised x it runs 82.
My minx, is not sensitive to trim at all, as a matter of fact it runs its best speed just a few bumps up from the bottom.
My 18 with the 400 and alpha ss picked up 3-4 with it over the std alpha. It ran just at 70.
I am not sure i am doing the right thing with the minx, just that I am in muskoka and everyone has a 22... I want to be different.

[Greg Guimond]

GT-21 is "different" in the Northland and it's a wrap at 80mph and $40,000 on the first day you take Title.

[craigdskilling]

Rbt I live in Kitchener ontario and I just finished my 350mpi.I had mod fathers put a whipple on and set it up now pushing 500hp and then some it sounds like you are close by. Why I say this is that when I bought my whipple drone them for great deal they had 2 with no hours on them cheaper way to go and looks cool. Thanks craig

[RBT]

Craig, what hull are you running? What were your before and after results?

[osur866]

Ill start out by saying I don't have a Minx but I'd think a nice warmed over 383 or boosted SB would prolly handle better in the Minx hull, I know when I took weight out of the back of my 18 it did run flatter but was faster and handled much better. I did an Imco -2 when my engine was stock and I saw hardly no increase in speed maybe 1-2, however it did improve handeling, I've never run the stock Bravo lower with current power but I'd guess it would slow it down 3-4, most of the conceses is with the -2 Imco you don't see much gain in speed until you get at around 70 or so, the Imco case is a lot different than an Alpha SS and the Alpha SS is actually -2 3/4" I believe with much less of a case your dragging thru the water. As far as a blower Vs. a stock SB and weight, I know for a fact my Whipple EFI is lighter than the stock intake was not by a ton but it is, I also added aluminum heads, ill bet I've taken out around 140-160lbs out of the back of my 18 with exhaust, heads, and intake over a stock set up and my boat likes it, idk what the Minx will do account a different bottom but I'd think less weight in the engine compartment would improve the handeling of it at higher speeds and when the boat leave the water. Good luck with your project in whatever direction you decide to go and keep us updated, not many have played with the Minx to achieve the speeds you are after, should be a cool project and one that many can learn from.
Steve

[craigdskilling]

Rbt my boat is a 1984 classic with Blackhawk drive.i was running a 383 last summer 375hp at 75mlp+ with 27p props.i just got my motor back from mod fathers last week so it is up at ron banks being rigged.Should have it back in 2 weeks.If I can help out a fellow donzi member please let me now. call.(519)465-4910 thanks craig.

[gcarter]

My minx, is not sensitive to trim at all, as a matter of fact it runs its best speed just a few bumps up from the bottom.


My Minx w/a 22" Hydro Q4 was extremely stable. It liked a LOT of trim. It performed best w/the indicator up about 75%, then a bit more and it would chine walk, but it would never blow out. My 2nd favorite prop was a Turbo w/the same pitch.
I believe if an additional 50-75 HP had been available, it would have hit 70.

[joseph m. hahnl]

There's only a 75 lbs difference in iron,an aluminum top end would fix that:lookaroun:.The Bravo puts it at a disadvantage with the parasitic drag too:doh:. I really don't see why every one is so negative:shocking: It's all geared up for a big block already :propeller: Drop :smash: and Plop :drive: Bro:cool:

[Greg Guimond]

While it would be a cool project and RBT has all the skills and access to make it happen, you still have to ask yourself how much value you place on your personal time. Is it $25, $100 or $200 per hour. Even if you are willing to throw a super low number like $25/hr at the project just as a tracker, how many hours will it take to complete? Is the 502 really free and all is all the glass and paint really free? If you really keep track of the expenses without labor, it will total up to $15,000 out of pocket quickly by projects end.

You would certainly want to talk to a couple of Minx owners who actually run BBC power and see what they say about balance, handling, attack angle and re-entry before you invest the time and money only to be bummed out with the result. At least I would do that if it were me.

I love spending other peoples money. I'm still leaning toward selling the Minx for $10,000, and buy the GT-21 for $50,000. Then you are boating next week for $40,000 USD.

[Greg Guimond]

And the only reason I slant to the GT-21 is that it is extremely rare to find a boat that underwent an open check book restoration and is so well sorted out. I'm going to say (regardless of the Donzi model) you might see a quality resto-rod piece like that come around once every 5 years.

Just my .02 :sombrero:

[RBT]

My boat came with a turbo 24", was banged up and ran like crap. I found an old 23 cleaver that works a lot better.
That GT21 is beautiful, I have plans similar for my minx. Reso mod. Are there or is there more info on this site about that boat?
As for the cost, my time is free. It keeps me from doing other stupid things which might cost even more money!
Yes there will be parts expense, but I really love projects. On scream and fly there is a massive thread about me building a plug, then mold, then building a Kevlar infused boat from it. Once done, I sold it. Next project.

Back to the matter at hand, I am curious to what you guys think will be the speed gain from the 350 to the 502?

rt

[gcarter]

I suppoose it has a lot to do w/HP of the 502.

[gcarter]

I guess the consensus is -3 MPH for the Bravo and maybe + 5 MPH per 50 HP increase ?????????

Maybe that would be the case if you used my old Minx w/an Alpha as a base.

[Greg Guimond]

That GT-21 is beautiful, I have plans similar for my Minx. Resto mod. Are there or is there more info on this site about that boat?

Yes there is a lot of information here about that GT-21. The short version is that the owner and builder of that GT-21 has extensive experience with a wide variety of I/O powered performance boats. He has had the high end Poker Run hulls as well as the small Slot Car hulls so his experience is roughly 16' to 36'. Guy knows his chit when it comes to restorations and set-up. His 16 Classic is running a consistent 80mph+ with full fuel load on GPS without blue printing the factory bottom. If you got your hands on his GT-21 I'm seeing a VERY big top end number, perhaps a 90mph tickle when conditions are perfect? It would be tight, but you could get there. You'd be crazy not to call him and check into his GT-21. You could also buy a 25 degree 502MPI Magnum Warlock and hit 80 for $21,000. Did I just say that? Off to the woodshed for 24 hours.

[Carl C]

RBT, I see a lot of people trying to talk you out of this or steer you toward another boat. Then we have a picture of a minx literally flying across the water with a surface drive! You have a viable plan if the engine will fit. I say go for it. If this is a stock 502, since no one has answered your question, I will GUESS 75 mph with the shorty and right prop. Go for it man! There were a lot of naysayers on my repower thread when I put the 525 EFI in my 22C. Maybe that's why some board members don't post their repower projects here. This is the kind of thread I like to follow and I hope you do it and get it dialed in. Now warm that engine up, or add a pro-charger and you could be topping 90 when conditions permit. Get the full external steering on first or the steering popo will raid your thread! ;) Good luck.

[Greg Guimond]

There has to be someone on the board that has a BBC in a Minx that could trade notes. It could be a 454 Magnum at 385hp or 502 Magnum at 415hp. In that size hull you should get 1 mph for each 10 ponies you add to the mix.

[RBT]

Thanks,
I mentioned before in this thread that what got me going on this idea was in the mid 90's I worked at port Sandfield marina up here in muskoka. They had a customer who had hot knots restore his minx. It was all red. They put a new 454 mag (365 hp) and a bravo in it. I don't know what the x was but I am going to assume stock. If I recollect it had 27 mirage. I wish I knew more, he did give me a ride and it was pretty fast in its day. I know his name, but this isn't a place to say it.! He is a pretty big donzi fanatic. I think he has a newer 22 now ( Shelby) with a whipple on it.
Anyhow, the motor I can get is a 502 mpi. 415 hp. I would hope to see mid 70's
RT

[biggiefl]

I hope you are right but a 22c with the same setup is fetching mid 70's so you might be a little disappointed but it will feel faster than in the 22c. Either way I would go for it but you are already committed so keep us posted. One day I will get the 22c in the 70's. Right now I am happy with my reliable & efficient setup running 60's.

[BUIZILLA]

you stated earlier that lengthening the lower strakes would be easy for you, so why not copy the bottom of a 22, maybe lengthen the lower strake even more, sharpen the strakes, blueprint the bottom, core the bottom, double and gusset the rear stringer width, get an offshore front mount, new transom, double ram tabs and go for it...

you've already convinced yourself you can do it, and want to do it, don't wait on permission from us

:D :umbrella:

[Greg Guimond]

Anyhow, the motor I can get is a 502 mpi. 415 hp. I would hope to see mid 70's with a Minx

Come on guys, help a :canada: brother out with some data. Where are all the Minx owners ....... ?

[joseph m. hahnl]

It all comes down to slip #'s.:propeller: AND by no means is a Minx slow:boggled:. My 350 mag 21p ran 60 in the cold and 58 in the heat that's 4600 to 4800 Rpm. The current Phenix 400 same Mirage 21 Run's 68 @ 5250. I think if I pitch up and get some slip out I'll touch 70:crossfing:


http://ts1.mm.bing.net/th?id=H.4755092519585804&pid=1.7



The Low end torque Value of the Phenix is ten fold to the Mag 350. The Phenix will plane out at 1/4 throttle , where as the mag was to the hilt.:checkered: It also carries the hull at all Rpm's, And that is what you want is to carry the hull with out porpoising .

[RBT]

Come on guys, help a :canada: brother out with some data. Where are all the Minx owners ....... ?

I have not made up my mind 100%, but I know for sure I won't build a small block, it was stay as is or big cube.
I know there are big block minx's, that is what I really want to know about.

If/when I get to the restoration, now that you guys have me thinking there is a lot more i could do to the bottom. I was looking at it today on the lift and was thinking about extending the strakes to full length, and adding a third set, half side that end close to where the existing do, these would be half way between the lowest strakes and the vee. It would add a lot of lift, ride would suffer a small amount.
As for the steering police, it wil happen when a Full restoration happens, not with just the 502. No dual ram tabs, real tabs k-planes

[gcarter]

Come on guys, help a :canada: brother out with some data. Where are all the Minx owners ....... ?

I gave mine already......if you read it all.
350 Vortec w/an advertised HP of 315-325 and a 22" pitch Hydro Q4 would do 65 MPH, except on the hottest of days.

So, my assumption is if you subtract 3 MPH for a Bravo and add maybe 100 HP it looks to me like 70-72 MPH.

[gcarter]

.......maybe a better, or the correct prop, would help also if you keep it as is.

[gcarter]

If/when I get to the restoration, now that you guys have me thinking there is a lot more i could do to the bottom. I was looking at it today on the lift and was thinking about extending the strakes to full length, and adding a third set, half side that end close to where the existing do, these would be half way between the lowest strakes and the vee. It would add a lot of lift, ride would suffer a small amount.


Maybe a pad would be a lot easier.

There's been a lot of discussion on this site concerning full length inner strakes. It seems that early 18's w/sharp keels and full length inner strakes had some handling issues compared to later (what we would call more conventional strakes and round keel) due to excessive lift generated in the stern. Remember, that hull form only lasted for a few years. The inner strake length ratio in later 18's and 22's is considered "right" or "correct". I'm not sure I'd reinvent the wheel here!
Greg, on the other hand has some good experience adding pads to these hulls. Maybe he could comment on his trials.

[Greg Guimond]

I have not made up my mind 100%. I know there are big block minx's, that is what I really want to know about.

I'm curious, what is so appealing about the Minx compared to a GT-21?

[mattyboy]

a few thoughts most donzi hull designs have remained unchanged thru-out their lifetime. as george mentioned the 18 was re-designed from the full length strakes and true v to a rounded keel and strakes that end around 2 feet from the transomin 1968. the 16 and 19 were updated to incorporate the same longer strakes the 19 also picked up LOA as it went to a 20 and 21. the 22 except for the addition of a reversed chine has basically stayed the same. seems they think the round keel and longer but not full inner strake seems to be the way.

the 20 cig progressed in design as new technology was introduced from the original short strake round bottom to a longer strake round bottom to eventually a pad bottom.

one of the 4-winns u boats feature a full length inner strake and a round bottom according to published reports the test driver said it was out of control at high speed.

[biggiefl]

Yeah I heard the U-19 was downright dangerous and hence why most were sold with duo-props. Don't copy that design.

[RBT]

I have driven a U19, it wasn't that bad. It did high side turning.

Parnell's GT21 is spectacular. What is it running for power?, any shots of the engine room?.
My thoughts for the minx are similar to Parnell's. no holds barred.

[mattyboy]

not sure if it was the 19 or the 17 one had the full inner strakes the other didn't and they may have re did the bottom after the first year too.

Parnell's boat are awesome :yes:

on your Minx I think dumping a BBC and bravo would be a not so expensive project and if it doesn't turn out you can easily re-coupe that investment, major changes to the bottom could be a roll of the dice that may be a windfall or a total bust.

George said a BB 454 minx runs low 70's I would think a 502 would be a mid 70's with the right prop

[Just Say N20]

On my iPad so no pictures of Parnell's GT21, but it is a huge displacement NA engine with right at 700 hp.

He had some custom exhaust parts made. He mounted the headers on e opposite sides of the engines so they dumped forward. He had stainless pipes bent so the exhaust went down and along the stringers so it exited below the water line when the boat was at rest. Very quiet when at displacement speeds, but awesome once planed off.

[Greg Guimond]

That GT-21 has trick pieces everywhere you look and all tastefully executed under the resto-mod model. I don't see a consistent 75 mph on GPS out of the Minx with a stock 502 Magnum and stock Bravo One drive regardless of prop. You might just tickle it under perfect conditions and super light on fuel.

[Greg Guimond]

Trick out your Minx with double wackers on the backer ............ :rofl:

[gcarter]

Greg, nice photoshop!
Might as well be a couple of Seven Marine outboards.........

[Carl C]

That GT-21 has trick pieces everywhere you look and all tastefully executed under the resto-mod model. I don't see a consistent 75 mph on GPS out of the Minx with a stock 502 Magnum and stock Bravo One drive regardless of prop. You might just tickle it under perfect conditions and super light on fuel.

An Imco shorty was part of the plan and is worth 2-3 mph.

[gcarter]

Parnell's GT-21 is such a bargain.
I'm sure he's taking at least a $75K hit on it.
I'd recommend anyone that can afford it to buy it.

[Greg Guimond]

I agree George. Unlike most every boat, you could buy that GT-21 run it for a year, and if you did not like something about it, easily sell it for what you paid. At a minimum RBT certainly would get a ton of good ideas on what to do to a Minx if he still wanted to go down that path.

Anyone have a picture of Parnell's engine bay?

[mattyboy]

we have pics of it the club's website and facebook page think it was the 16th annual dust-off.

http://gallery.lgdonziclassic.com/main.php