17' Pre Alpha 300hp project advice needed

[Gumetina]

Hello,

I am Alex from Serbia, and i have a project boat that i am working on, its

Browning AeroCraft Malibu , 17' with broken 165hp mercruiser engine (i6) that i am trying to swap with Audi V8 (car engine) ABZ 4.2l v8, 300hp at about 6000rpm.
dyno graph

My sterndrive is Pre Alpha mercruiser, (has lifting eye) and serial number is 4628124 B....

prop on it is about 15 x 18 (measured by hand)
Final drive is 1.62:1

i have only two questions....

1. Will the pre alpha drive hold that power and torque?
2. Is my prop anywhere near good for the setup ?

I must add that marinizing and anything engine concerned is not a problem ....
Boat looks like this

it is 920kg heavy with stock engine that weights 250kg... new engine is 160kg

Kind Regards,

RAle

 

[HT32BSX115]

Re: 17' Pre Alpha 300hp project advice needed

Howdy and Welcome aboard!

The alpha drive will probably work best if kept at 5500 RPM and below. They are good for about 300HP.

The prop will depend on the drive ratio which for your engine (which I believe is about 1.65:1)

I am guessing you're be using an AUDI V-6 or V-8? neither will make 300 HP if you keep them below 5000 RPM........ You will need to make water-jacketed exhaust manifolds, and fabricate a bell housing that will connect to the Alpha transom mount. You'll also need to modify the flywheel to accept a coupler that will work with the drive. There is a LOT of other parts you'll have to fabricate to make it all work.

None of those parts are available so you have to make everything. If you have your own machine shop it's possible, but not very practical because there are engines out there that will work as good as the Audi that you can buy off the shelf parts for. I don't know about parts availability in Serbia. Maybe you'll be better off making your own parts. If that's the case, then you can probably make any engine work. The "big" stuff is the manifolds and flywheel housing/coupler.

Using a 1.65:1 drive on a V-8 is a little off, you'll need a higher pitch prop to keep from over-revving the engine. Most V-8's use a 1.5:1 drive ratio to operate a prop in it's most efficient RPM range.

If it were me, I would just get another 165 I-6 or a newer V-6 (4.3L)


What you want to do is possible (if you have unlimited access to a complete machine shop) if you make your own exhaust system, flywheel housing, flywheel, and MANY other associated parts.....

There will also probably be an exhaust reversion problem (unless you use "dry" stacks") since no Audi engine is designed to work with a "wet" exhaust.


I would just get an engine that the drive was designed to work with.



Good luck,


Rick

 

[Don S]

Re: 17' Pre Alpha 300hp project advice needed

You will need the 1.50 gear ratio, not only for the ratio, but for the heavier duty gears since you will be at max hp rating for those drives.
One other thing you need to look is some safety issues. In a boat, electrical items like distributers, starters, alternators etc. are ignition protected, so that should your NON-Marine fuel system leak, the electrical items will not ignite the gas fumes.
Fuel and Electrical systems are highly regulated for marine use for safety reasons.

 

[Gumetina]

Re: 17' Pre Alpha 300hp project advice needed

Thanks for a warm and quick response

Here, it is most unlikely to find any of the shelf parts, and that's probably why the original engine died, lack of maintinence and of course parts.

Machine shop is what i have, and run, we do car tuning and almost every day fabricate something custom ... so that should not be a problem.

For the exhausts, i want to use open exhausts, not through the Z drive, but free air... will that be a problem since there will no longer be flow of gases through the sterndrive ?

So You say that sterndrive will not be very happy with 6000 rpm ?

 

[Gumetina]

Re: 17' Pre Alpha 300hp project advice needed

I just missed Your post Don S,

I will be running distributorless ignition , and i alredy have explosion protected alternator and starter. also i have a fan that evacuates gases from the engine compartment... I will take caution

The gears for the final drive, where is the best place to look for them ? i can only pay by bank transfer, since in Serbia paypal does not work so ebay is out

 

[Don S]

Re: 17' Pre Alpha 300hp project advice needed

5000 is about max rpm for those drives.

You can go through hull exhaust, but it must be water cooled if under the engine cover, or you will build up way too much heat and set things on fire.

You are also going to need an ignition system you can use the shift interrupt system on. Without it, you will be have a serious problem getting the drive out of gear. Here is a thread on how and why the system works.
http://forums.iboats.com/showthread.php?p=1930449#post1930449

Your cooling system is also going to have to be designed to keep the water flowing through the exhaust, before the thermostat opens.

There are a lot of differences between the marine and automotive setups that aren't obvious.

 

[Don S]

Re: 17' Pre Alpha 300hp project advice needed

The gears for the final drive, where is the best place to look for them ? i can only pay by bank transfer, since in Serbia paypal does not work so ebay is out

I have no idea where you can get them. The other problem is, it takes a lot of special tools to put in new gear sets and get all the tolerances correct, especially when you want to push those old drives with that much power.

You might want to spend some time reading here as well. http://forums.iboats.com/showthread.php?t=329915

 

[captk]

Re: 17' Pre Alpha 300hp project advice needed

If still available the 1,32:1 might be abetter option. the 233 fords and the original 350cid 250hp chevies used them and they didnt come apart until the 260hp with 1.5:1. if not still available the forged hd 1.5 are good.

 

[Gumetina]

Re: 17' Pre Alpha 300hp project advice needed

Looks like i chose the wrong engine...
But it wouldn't be the first time we are putting something never meant to be there, so i am still an optimist.
I only fear the drive goes in to million pieces, since similar thing is almost impossible to buy here, or at least for a reasonable price
I will not stand down thou, i hate the outboards....

I will let You guys know where the build is with some more colorful data hopefully

Kind Regards,

RAle

 

[achris]

Re: 17' Pre Alpha 300hp project advice needed

A while back a guy in Melbourne put a Holden Commodore 3.8L V6 into a 20' Bertram. He made a lot of custom parts and documented the whole process here. I've looked for his posts but can't find them. I can't remember his exact user name but it was something like 'alfaname'.... Anybody else remember that?

Chris....
EDIT: found the thread. Well worth having a read... http://forums.iboats.com/showthread.php?t=369819