Derating 350hp for an Alpha I?

[SFT2]

I'm looking at a project boat that has a good hull, deck, and engine, bad outdrive and vinyl. It's cheap enough that I can afford a new upper and lower, and custom seating and side curtains, and still come in under budget. However, the engine is reportedly a 350 horse 350 and new enough it's not even broken in yet. I suspect it's just too much for an Alpha drive and replacing the blown up lower unit will just result in a newer blown up lower unit before long. I've come up with two possible solutions: a. switch to a Bravo I, b. detune the engine to 300. My suspicion is that the Bravo would be a very, very expensive way to go and would involve substantial changes to the transom. Unless I'm mistaken about the work involved I'd say that route is out. Detuning the engine, however, is a bit less complicated. Throttle limiter, carb restrictor, cam change, etc.

Question is, should I ignore it because I'm being paranoid, or go with choice a or b?

 

[Flukinicehole]

Re: Derating 350hp for an Alpha I?

Depends on how your gonna drive the boat. If your gonna hammer it out of the hole a lot then it's not going to hold up. If you are going to ease into the throttle then it is going to last a long time. Do you do a lot of skiing, wake boarding etc? If not then go with a replacement.

 

[Bondo]

Re: Derating 350hp for an Alpha I?

Ayuh,....

The Simplest possible Fix,...
Is to Not Slam the throttle to WOT.......
And,...
I seriously doubt your motor is making 350hp, at the rpms that we run....
If it Is,.... Drop a 2bbl. Carb on it,... Then it Won't.......

Btw,... Your Right about the Bravo swap,.... You'd be changing Everything aft of the rear motor mounts,+ a few things forward of that.....

 

[FreeBeeTony]

Re: Derating 350hp for an Alpha I?

I keep watching these threads about the 300HP rating of the Alpha........I still (as a project someday) would like build a 383 Stroker for my 24' Grady.
It seems the general consensus is that if you don't beat on it (my Grady is far from a speedboat) the Alpha would probably handle a nice torquey Stroker.

Also.........I saw mention that the Alpha's 300HP rating was at the prop and not the crank. Anyone know which is correct?

Mind you, I haven't even tested my RapidoVortec in the water yet..........and I'm thinking of this kinda *****...........I really don't mind playing with wrenches and my kitchen project is coming to an end soon!!!!!!!!!

Here's looking at a good season to all..............

 

[backwater dawg]

Re: Derating 350hp for an Alpha I?

I think the comment about not to hammer is boat out of the hole is correct. I have a 28' Regal with twin 260's--Alpha drives--2400 hrs--original Drives---I bought the boat new and EVERY time I put the boat on plane I run the manual trim tabs all the way down and just bring the throttle up normally---not just hammer it--bring it up slowly and let the tabs do the work and the Alpha drive will last a long time--I would'nt spend the $$$ to replace it or detune the motor---good luck Steve

 

[Haut Medoc]

Re: Derating 350hp for an Alpha I?

Stop being paranoid & go easy on the throttle.....
I doubt the HP is right as Bondo says, & I would try it out as is.....
Then throw the 2 BBL on it, if you need to.....​

 

[SFT2]

Re: Derating 350hp for an Alpha I?

I'm old enough that I don't do dumb thinks like cram the throttle forward so hard it bends the lever when it hits the stop, so maybe I'll be ok with the 350/350 and Alpha. Maybe there's some truth to the rumor the SEI legs are stronger than Mercruiser's, too. Ok, I'll take off the tinfoil hat, take a look at the hull this afternoon, and, if things look good, whip out the credit card and give SEI a call tonight (unless I find a dealer in Houston, anyway).

Oh, I plan on pulling skis, wakeboards, tubes, etc., and I doubt the people on the wet end of the rope want their arms removed from the sockets, so that'll help with keeping the gears from turning smooth on me.

I'm glad my homework on the bravo was right. I also suspect that it makes more power vanish before it gets to the prop, too.

I'm almost scared to know what this boat (19' Wellcraft Elite) will do with this setup. It originally had, I believe, 200 HP. It reportedly drove very nice, and very briefly, with the new motor.

 

[HT32BSX115]

Re: Derating 350hp for an Alpha I?

If I was going to buy a project boat with that kind of HP,

I would look for a Bravo drive and transom. (even consider a Bravo III if your boat is a cruiser)

Have a look at Ebay, there's usually a LOT of Bravo stuff there. also check the locals....I bought my complete engine/transom/drive from Craigslist! out of a wind damaged Bayliner.


Cheers,


Rick


Oh by the way, NO "substantial" changes to the transom other than drilling a couple of extra holes......AND I swapped out a King Cobra for a Bravo III !

You will need to add a raw water pump to the engine though... There's always a couple of those on ebay!

 

[180shabah]

Re: Derating 350hp for an Alpha I?

Oh by the way, NO "substantial" changes to the transom other than drilling a couple of extra holes......

Depends on the age of alpha. GenII's already have the two "extra" holes.

 

[SFT2]

Re: Derating 350hp for an Alpha I?

I went and looked the boat over today and wasn't overly impressed. I can get it for $700, quite likely less, but it's going to take a LOT more work than I expected. I can see the teeth missing off the driven gear in the upper unit, but the seller mentioned something about a mechanic saying it was run without oil, which sounds to me like both units are toast. I'm going to think it over quite a bit, and follow a few leads on an outboard for the boat I really want (Baja that needs carpet, seats, and lots of horsepower). We'll see how this turns out...

 

[John_S]

Re: Derating 350hp for an Alpha I?

Take what you can see and multiply by three.

 

[mkast]

Re: Derating 350hp for an Alpha I?

Change the gear ratio from 1.5:1 to 1.32:1.
Will handle the torque better.

 

[tmh]

Re: Derating 350hp for an Alpha I?

A fried engine produces no torgue! You'll be fine with the Alpha if the engine doesn't work.

Seriously, for $700 of course the engine is toast OR just buy it and part it out!