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Amalfi
07-31-2006, 06:56 PM
Have just purchased a 1986 minx and it is laying in storage until I get back home in September. A freind closed the deal for me so I have not even seen the boat except for a couple of pics. As this is going to be a full restoration, back to her original glory so far as is practicle anyway, I was trying to locate any form of documentation, brochures and ultimately plans on the 1986 Donzi "Minx". My question at this time though is does anyone know the transom angle of this model?
Many thanks for any info. Tony.

gcarter
07-31-2006, 07:08 PM
I would say the last 5'-6' of a Minx is identical to a 22C.
But if I were you, I would change the design of the instrument panel. Not only are the gauges no longer available, but many of the wiring components, switches, and breakers are downright unsafe.
There have been a few promotional pieces posted to the board (you might do a search) and I have posted some restoration pictures and suggestions.
Like this one;
http://www.donzi.net/forums/showthread.php?t=36703&page=1&pp=15

Also please post your hull # so I can include it in my list;
http://www.donzi.net/forums/showthread.php?t=39260&highlight=minx+hull+numbers

Amalfi
07-31-2006, 07:43 PM
Thanks for the links, I will check them out for any leads.
The HIN is DMR20039L586.
The boat will be gutted and redone entirely. From bow to stern all will be removed, inspected and the appropriate action taken to either restore or replace and improve without taking away her original wow factor, the goal is to enhance the design and function. Hope to be doing runs to Stiltsville and Bimini by November. Got some late nights ahead, so trying to get all my home work done now so as to get a good jump start.
Thanks, Tony.

gcarter
07-31-2006, 08:49 PM
Sorry, I should have mentioned that first and last name, boat and trim colors are also useful.
Thanks.

MOP
07-31-2006, 09:02 PM
11 Degree's is pretty standard on our boats.

Phil

Amalfi
07-31-2006, 10:35 PM
George, the name is Tony Hodgson, the hull color is flag blue with blue boot stripe separated by white. Top side has blue spine trimmed by a red pin stripe on white surrounding deck areas and cockpit.
Thanks Phil for the info on the transom angle, 12 degrees was what I was hoping for, but I will take 11.
The restoration of the Minx will take place at a shipyard, coinciding with the maintenance period of a much larger vessel I work aboard. Counting on the shipyards resources at my disposal will expedite my restoration. Have glass, carpentry, electrical, hydraulics, metal fabrication and spray booth facilities all on site, talk about convienience hey!
My engineer is building a 383 producing 477 hp@6000 and 490ftlb@ 4500power plant to replace the old 260 hp unit that takes up the space at the moment. The fact that he used to build 2000 hp screamers for the Castrol drag racing team in New Zealand has me feeling very confident in the figures we have arrived at on paper.
Only area I haven't nailed down at this point is the need for a Bravo outdrive and S/S jacketed headers. Any links or contacts in this area guys?
Cheers, Tony.

gcarter
08-01-2006, 06:47 AM
Tony, I like your attitude. Do it once and do it right!
While your at it, don't forget the fuel tank.....takes a few weeks to order one.

BUIZILLA
08-01-2006, 06:48 AM
6000 rpm is a tad aggressive doncha think?

MOP
08-01-2006, 07:20 AM
Need to start thinking Adrive or Grenade time!

Amalfi
08-01-2006, 09:34 AM
My mistake by not indicating a barvo 'X' drive. It's a starting point anyway.
I know the figures are excessive on the donk, but one day this engine is going into an old pick up I have plans for, hence a closed loop cooling system on will be added to the engine. As far as me actually running around in this thing at 6000 rpm, highly unlikely. My car says 120 mph on the speedo but I don't run around at that. She will be a inter-coastal cocktail/dinner date cruiser with serious water sports on weekends. My hardest runs will be to Bimini, the Keys and Stiltsville and that will only be attempted in ideal conditions, running conservatively for range. So im cofident a Bravo 'X' will provide dependable performance. I guess it's how you drive it.
Many thanks for the comments though. It helps me consider other options that I may have overlooked. So, any leads on a bravo drive and jacketed headers would be appreciated.
Tony.

Woodsy
08-01-2006, 10:57 AM
The cam you need to run that motor to 6000 RPM will cause reversion... you WILL hydrolock your motor..... There are a bunch of threads on camshaft duration and reversion. Have your Engineer do a search if you don't quite understand it....

Of course dry exhaust solves this particular issue.... but its VERY LOUD and usually frowned upon by the local water cops.

Build your motor for 6000 RPM, but cam it for peak hp/torque around 5100 RPM. Your drive and your wallet will thank you. You can always swap the cam when you take the motor out. Your Bravo X drive will not live long at 6000 RPM... the harmonics of two 90 degree power transfers will it apart!

Woodsy

Amalfi
08-01-2006, 11:23 AM
Are you refering to degrees of valve overlap? I have a custom cam form comp cams with 55 degrees of valve overlap. Would this suit? I don't plan on running the engine to 6000 rpm. My max torque is 490 @ 4500 rpm which is a great figure I thought. My maximum efficiency is 92% @ 4500 rpm also, so I will be spending my time under 5000 rpm for all the right reasons. Now the exhaust side of things I don't understand, so if I am still going down the wrong path I would welcome any advice.
Tony.

gcarter
08-01-2006, 11:26 AM
Hmmm...jacketed headers only have a two year warranty, don't they?
How about Stainless Marine manifolds, will probably last longer than you care to own the boat. Also they're in your back yard.

Another subject....I had RDS modify my new fuel tank to be 3/4" deeper and picked up another 4-5 gallons.

http://www.donzi.net/forums/showthread.php?t=36420&highlight=tank

I think their prices have gone up since then.

These 20 year old boats do deteorate somewhat.:yes:

BUIZILLA
08-01-2006, 11:27 AM
IMO, thats WAYYYYYYYY tooo much bumpstick

fax me the cam card

305 592 5936

Jim

Amalfi
08-01-2006, 11:45 AM
I will heed your advice and pull the existing tank out for inspection. I like the sound of more fuel capacity for the longer runs. Yes, Stainless Marine may be the way to go, I'm still in the early research stages of many facets of this project. I plan on fitting the silent choice diverter with what ever system I end up with. A rev limiter to keep the rpm max at 5000 may be something for me to consider also.
Tony

Cuda
08-01-2006, 07:18 PM
Tony, I like your attitude. Do it once and do it right!
While your at it, don't forget the fuel tank.....takes a few weeks to order one.
Five weeks to be exact. :(

Mine had better be ready by this weekend.

Amalfi
08-01-2006, 07:36 PM
Woodsy, I've been trying to understand the 'reversion' that you described. Can you put it to me in a nut shell how this occurs? Again, the cam I am using has a 55 degree valve overlap at seat with only three degrees at 50 thou. on lift.
I will not be running this engine at more than 5000 rpm in this application.
Is this something that is related to the exhaust system side of things more so than the cam? Any comments appreciated.
Tony.

Woodsy
08-01-2006, 08:30 PM
Amalfi...

In simple terms...

Reversion in a nutshell is exhaust coolant water being sucked back into the cylinder bore. The duration of the exhaust valve opening is the culprit. There are far more knowledgable people than I on here such as Rootsy and Buizilla (to name a couple) who can expound on this topic.

It seems to me your not really understanding the concept of a marine motor and how they work. You are applying a "car engine" mentality to a marine engine.

RPM is not the friend of your outdrive. Outdrives such as the Merc Bravo have two 90 degree transfers of energy. The faster you spin tose gears, the more harmonics (wobble) they produce. This leads to an inevitable catastrophic failure of your drive, usually the upper....

Horsepower is your friend but it really only helps you out on the top end...

Torque is the kingpin of a marine motor. You need torque to spin those propeller blades. Torque is what gets you out of the hole and your midrange acceleration. Of course there is a torque limit to the Bravo drives as well, but as a rule the lighter the boat the more torque a drive can take....

So now you see the problem... you want as much torque and hp as possible, but your max RPM is limited by the sterndrive. This is why big cubic inch torque monster motors are the favorite choice.

There is no need to reinvent the wheel.. You want to cam your 383 to make its peak torque around 4800-4900 RPM and the HP peak to be right around 5100 RPM. I would go with a cam grind similar to the one Mercury Racing used on thier 377 Scorpion motors... why mess with a formula that works?

Woodsy

Amalfi
08-01-2006, 09:42 PM
Woodsy, thanks for the expaination. I was misreading your original message.
This is what I and the engineer thought you might be refering to. Information that I have discovered just now talks about cam selection to avoid reversion. It suggests a cam of no more than 240 degrees duration @ 50 thou. The cam we have chosen is 224/230 @ 50 thou with 112 degree lobe centers. I beleive I should be safe with this combination. As far as our torque goes we have 460 ftlbs @ 3000 rpm thru to 490 ftlbs @ 4500 rpm. This is a comp cams marine application cam shaft matched to the rest of our specifications such as heads, induction, compression ratio etc.
I guess the only other area that I should be looking at to combat 'reversion' would be the exhaust system, i.e. riser height and collector length.
As I am blanking off the transom completly and starting from scratch I should be able to configure a decent angle on the dry collector length to its exit point thru the transom. Whats your preference when it comes to marine exhaust systems just out of curiosity?
Thanks for the feed back.
Tony.

gcarter
08-02-2006, 06:14 AM
BTW Tony....Happy Birthday!
:happy_bi:

Rootsy
08-02-2006, 06:45 AM
standard "rule of thumb" with a sbc marine camshaft, for any type of stock or short to medium riser length wet exhaust.. is NO MORE than 224* of duration @ .050... most marine camshafts run in the neighborhood of 112* of LSA also to keep overlap down... i tend to push it a tad more with good exhaust... and the bigger the CID the more you can push it... 383 should be able to get away with maybe 230 if you have a good aftermarket exhaust that will put the water in the exhaust stream further from the manifold... or jacketed full length headers would be cool..

reversion happens at idle and low rpm operation...

i also tend to push the RPM envelope with sterndrives... though i really like to limit my WOT rpm to no more than 5500 or so... but be aware if you do so you take your chances... it's not really the lower end you need to worry about... that end is much more stable than the top direction change... just not enough bearing and shaft support to keep things from distorting under high load in the tops... remember, gears want to climb out of themselves as they are loaded...

Amalfi
08-02-2006, 09:27 AM
George, thanks for the b'day reminder. I'll go out for a beer tonight if we get to a dock!
Woodsy, I sure I'm more of a conservative helmsman than you may be, so your comments were re-assuring to me regarding the set up I am planing to go with.
I will be going as high as the space will allow with the riser and will exit the transom somewhere between boot stripe and the plane of top of drive. Obviously, flappers in exhuast tip or over end of exh. tip will help. Is it acceptable to have both, or choose one or the other?
Cheers, Tony.