alpha one gen one outdrive question

[heyu29h]

I have a 18ft cris craft with a 200hp 305 gm mercruiser with a broken alpha one gen one sterndrive. 1986

I also have a alpha one gen one sterndrive from a 120 hp 2.5l in great condition. 1985

my question is, could I put the good sterndrive from the 120 hp on the 200 hp? I know there is a gear ratio difference, but I did some math and figured distance traveled by rotation of prop at 4500 engine rpm and if I use a 21pitch which I already have, instead of the 17 pitch which is currently on 200 hp, I would get roughly the same distance traveled per rotation on the 120hp gear ratio with a 21 pitch, that I was getting on the 200 hp gear ratio with a 17pitch.

is there any reason this won't work? I am very limited on money, and am trying to use parts I already have, so we can at least use the boat again next summer.

note the old 200hp is outdrive is not fixable, hit a stump, n broke it to pieces!

thanks in advance for any advice!

 

[alldodge]

Re: alpha one gen one outdrive question

:welcome: to iboats

I see of no reason it will not work, your performance could be the only issue. Only difference in the alpha as you mentioned is the gear ratio, the hp change will have no effect on how long the drive. What is the difference in the drives ratio?

 

[dn010]

Re: alpha one gen one outdrive question

Just a heads up - they're called Alpha 1 drives/parts, not Alpha 1 "Gen 1". It will work as far as bolting it on, they're the same drives however the difference in ratios are 120 is 1.98 ratio, & 200 is 1.65. If I were you, I'd look for the correct ratio drive...

 

[harleyman1975]

Re: alpha one gen one outdrive question

I think your on the right track. As others have said there may be a performace issue but you can prop for that...but if it means the difference between boating and watching from shore, well, that is a no brainer. With the 17 pitch prop it will have a great holeshot but over-rev so yeah try 21 or 23 pitch prop and watch your tach.

 

[Bondo]

Re: alpha one gen one outdrive question

Ayuh,.... I'm gonna disagree,... While the math might say it'll work,....

My experience says ya Ain't gonna be Happy,....

 

[thumpar]

Re: alpha one gen one outdrive question

I agree with Bondo. Some people have got away with going from a v6 drive to a 120 drive but you are going the complete extreme.

 

[dn010]

Re: alpha one gen one outdrive question

+1, I agree to this too as you probably already read in my post.

You're putting the boat away until next summer - that's plenty of time to do it right & look around for an Alpha 1 with the correct gear ratio.

If you can't buy a brand new one, a used drive alone can be found [at least down here] anywhere between $100-$500+; most people want to get that old boat out of their yard and take whatever they can for whatever is left installed on it. As with anything used, a good inspection before you hand over your $ is a good idea...

Ayuh,.... I'm gonna disagree,... While the math might say it'll work,....

My experience says ya Ain't gonna be Happy,....