Mercruiser outdrives, some info please....

[Valv]

I would like to know if somebody can tell me the difference between Mercruiser #1 and Alpha 1 outdrives. I have my project boat on rebuild, and I purchase at a good deal a complete Alpha 1 gimbal housing + rams + Drive. Unfortunately I found out my gear ratio won't work with V8 (thank you ODDD1). I have a good offer for a Mercruiser #1 from a V8 (1.50:1 ratio) and they told me it will fit on Alpha gimbal. Is it true ? Also which is better between the 2 units ? I would like to go Bravo but my budget is very limited now and I'll have to pass on it, but I'd like something "beefy" for a 26' Searay. Alpha are not the best but it will work, how about Merc #1 ?<br /><br />Thanks guys for all your help, I wouldn't even imagine restoring a boat without all the infos I've got from this site.<br /><br />Val

 

[ODDD1]

Re: Mercruiser outdrives, some info please....

VALV, do I got news you need......here is how it breaks down.....historically, the first merc drives were called I's..used in various forms from 60's to about 1978....then an internal redesign of the lower case an was called a IR.....in 1984 a cosmetic change in the upper and lower cases, plus a major redesign internally of the lower case made it a MR, later to be called an alpha....<br /> Now, what fits what???<br /> gear ratio is determined by the upper case...use your 1.50 upper half, the cosmetics dont match but all bolt patterns, shafts do.<br /> bolt on your existing lower gearcase off your 'wrong' ratio drive, you will have the stronger lower end that way ..... <br /> so what do you end up with? a alpha transom plate, older style upper drive,[which internally is th same as an alpha]..an an alpha lower unit , all without any regearing/shimming of the cases....cheap an effective...

 

[Valv]

Re: Mercruiser outdrives, some info please....

ODDD1 I have the upper for the Alpha only, no lower but #1 is complete (minus prop). I really appreciate your reply and I will purchase the Merc #1. It's amazing how useful this site is.<br />THANK YOU VERY MUCH !!! You made my day !!!<br />Just out of curiosity, which drives were installed (before Bravo) on large boats ?<br />I know Bravo are the "heavier duty" drives now, but what about before 1985 ?<br /><br />Thanks again.<br /><br />Val

 

[ODDD1]

Re: Mercruiser outdrives, some info please....

big block on a stern drive pre 1988 needed a TR drive, with requisite transmission behind the engine....racy boys used the TRS, which had a smaller an faster lower unit than the TR...sorry to hear you dont have the alpha lower...the 'I' will have to do....

 

[wbrannies]

Re: Mercruiser outdrives, some info please....

I have a # 1 upper and gimble

 

[JB]

Re: Mercruiser outdrives, some info please....

Moving to I/O and inboard.

 

[Bondo]

Re: Mercruiser outdrives, some info please....

If you're using the Alpha1 transom/ gimbal assembley, You'll have to switch the input shafts....<br />The Alpha1 transom/ gimbal uses the 9"+ input shaft... The Mod.1 uses the 8"+ shaft.... <br />If you don't do the switch, It'll run, For Awhile.... <br />Then the Coupler will give out.....