Performance Upgrade Suggestions....80 MPH??

[Stix Magill]

Hello Speedfreaks!

I would like for you guys to suggests various ways for me to upgrade the performance of my 1987 Donzi 20 Minx. It was repowered in 1997 with a crate fresh 350Mag (270hp?) and has the original Alpha1 outdrive.
I would like my upgrades to be as nonobtrusive and cost effective as possible. Is 80mph possible with the Alpha
1?

Other details:
*Mirage 23 Prop
*K and N Airfilter
*Through-hull 4" pipes with Shotgun
Silencer tips
*top speed 62mph (on the speedo) at WOT,
4700 rpm with low fuel

Thanks for your help!!

Scott Smith
"Stixmagill"

[HP 600SC]

Unfortunatly the only way's are:
supercharging, turbocharging, or nitrious
any of them will grenade your alpha drive first, then your engine.
you will have to upgrade your engine and your
drive to get anywhere near 80 MPH.

[CDMA]

An Alpha one can only really take 350 hp +/- . Which might get you into the mid sixties but sure not 80 mph. I feel your pain with that alpha. I have an 18 classic with a 260 merc/ alpha. I would love to build a 383 but I worry about blowing the drive. I hate being towed in or losing a good day of boating. The 22 will take a few more hp whane it is done though... :eek:

Chris

[Barry Phillips]

Stix: 80mph out of smallblock and a alpha in
your Minx would stress both to the point of
being on unreliable. I know of 22s on this
site running in the lo to mid 80s with
HP-500s makeing 550+ hp. This kind of HP
will blow your Alpha into the after life.
Your are going to need a Bravo and a hot,
perhaps supercharged 454mag or 502 to make
those numbers. I really love the Minx, I almost
purchased an 87 several years ago. One of
the downsides to this boat was the small block Alfa powertrain, which pushed it 58mph, I knew I would not be happy with this kind of performance. 80mph is a big number and to obtain it you are going to need a Bravo and a strong running big block.

Goodluck
SO-SLO :cool:

[Sam]

Scott, did you get those shotgun tips from that guy I told you about.

Sam

[Stix Magill]

Sam,

Yes I did, and thank you!

All you others, thanks for your input. I was hoping thee would be a simple way to add a little speed. If I really feel the need to get faster, I guess I will buy a different boat. I believe I can learn to live with 60+ MPH. Fresh motor runs like a top and it's the coolest boat on my lake. It is easy to see the bright side there!


Stix Magill :)

[Cuda]

Where can I buy the shotgun silencer tips?

[Stix Magill]

Cuda,

I found these used with Sam's help. You can find them new by searching the web for "shotgun tips exaust" or something similar. I don't know the manufacturer, but I can find out this weekend when I am at the lakehouse if you need the info.

Scott

[BRIAN73]

Cuda,
The Shotgun's are made by Drew Marine. I bought a set three years ago. They went on easy and cut the noise a little. I sold them when I gave my 350, $2700.00 worth of mods. I think they run about $500 a pair. If you buy them, get the set that diverts the exhaust toward the water.
Brian

[Randy Hibbard]

Hey Stix, it's great having the coolest boat on the lake you bet! These guys are all correct in the limitation of our 350 Alpha combo. I did the same search for speed now for two years. After countless advice from our Donzi friends and maybee 3 grand in parts, my Minx is'nt much faster than yours. I did heads, cam, intake, exhast, all that and now get maybee 65 out of her with 2 people. This speed is getting the boat quite loose on even smooth water. I finally just decided to enjoy the boat as it is and accept it when I loose a race to a steped hull big block boat that costs 80 grand.(These guys are allways impressed that the SBC can even run with them at all.) You've got a good prop and set up, I would enjoy what I had insted of spending money on an allready great running combo. I wonder how Tory is doing on his Minx? Take it easy.

[Randy Hibbard]

Oh, buy the way Forrest, I would be happy with 8 mpg! How do the guy's with twin 500's afford it? must be nice....

[TORYSMINX]

I wrote a version of this to Chris earlier this morning

Status of the Minx:

Well I put the Minx away right for the winter and I am rejetting the carb
over the winter. I was running so rich even with all of the adjustments and I
could not turn more than 4400 when the trim was down.

As you may know already I completed the 385 cu in stroker and I have still been making adjustments.

The best I got on the speedo this year was 73.5 mph with 3 people in the boat and
I was pretty happy. But the drive is going south soon. There is all sorts of
play and it is a handful going fast.

I will say one thing about the accelaration it is real quick out of the
hole(well going from 20-60).So if I were to do it all over again I would have gone out and bought a 22 classic 502 and maybe would have thought twice about dumping the 9-10k into this thing. Granted it has some very good parts in it.


I am going to keep this boat for a while cause I have alot into it.My next step is going to be cosmetics.

As for 80mph gps this setup will never see it I think. So It may be easier to drive and enjoy the boat since it runs fine as it is.

If you want more speed I think you can get a deal on those hydrostream 16 footers with 250 hp or so(One of those ones that do like 90 on pond water) This way you can get the speed kick out and enjoy the minx..

Tory

[Stix Magill]

Randy,

Thanks for the input and comments. Like you said, I am going to enjoy the boat as it is ( fresh stock engine) and maybe try a Turbo prop. My summer home is on a winding river and 80 mph would be absurd and very dangerous. I mentioned that number to peak interest in the thread. I was hoping there was a relatively inexpensive bolt-on that might add 3 or 5 mph, but I guess not. When I read about all the fellows spending so much time tweaking their boats, it makes me glad that I am running stock instead. Maybe a little slower, but cruising every weekend none the less. There may be a day in 5 years when I consider a 22 Classic with a 502, but until then, the Minx will get me where I'm goin' on time.

Preparing for the weekend Donzi rides and wild boar hunt,

Scott

:) http://stixmagill.homestead.com/files/donzifast.jpg

[James McCommons]

I know of a way to pick up 3-5+ mph. I have a Alpha 1 SS drive for sale on this site. It is a bolt on and takes @ 1.5 hours to replace drives. I have a friend with a 20' Minx with a 320hp F.I. Mercruiser w/Alpha 1 ss and runs low 70's. I have a 22' Classic and am building a 385 C.I. engine at this time. I will report on how it runs as soon as it is finished. I am running an Alpha 1 drive that is raised and cannot use the SS.

[Stix Magill]

I will look into the Alpha SS drive. Where can I find information on this drive?

Stix