MerCruiser ALPHA ONE 1.32 Gear Ratio Upper Unit on a GM 5.0/5.7

[jbutler67]

Any issues using a MerCruiser ALPHA ONE with a 1.32 Gear Ratio Upper Unit on a GM 5.0/5.7L?

Upper unit has a 1.32 gear ratio.

Engine is Mercruiser with s/n M048938, so a 5.0 or 5.7L?

I’ve read the following gear ratios to engine:
1.32/1.29 for big block V-8s
1.50/1.47 for small block V-8s
1.84/1.81 for 4.3 V-6
1.65/1.62 for I-6s
1.98/1.94 for I-4s

Thanks

 

[Bondo]

Ayuh,...... It'll be a Dog with that ratio,.....

The 1.32s are very rare,..... I'm surprised you found one still serviceable,...... the gear sets are NLA,....

 

[Walt T]

Definitely not. Don't use it. I'm up in altitude in Colorado and big blocks here don't use that ratio.

 

[alldodge]

IMO, It will work but will need to find a low enough pitch prop

Depends on how much room is available
If current prop was a 21, you can drop to a 15, but if it was a 17, going to a 15 may not be enough

 

[Scott Danforth]

If it was a really small hull and a 5.7 or 6.2, maybe

 

[thumpar]

I would sell the 1.32 to someone with a 7.4l who can't find one any longer. They are super rare. You should be able to get a 1.5 or thereabouts and maybe some extra for fuel in the deal.

 

[SeaRayKindaDay]

Like everyone else has said, a 1.50 will better suit you. They are very easy to come by at a good price. I'd recommend that vs sizing and buying a new prop just to get that 1.32 sort of working.

 

[achris]

What boat is the engine in?

 

[jbutler67]

Thanks all. Boat is a 1986 Rampage 24 Express. Has the 1.32 upper unit on it now. At least that is what is on the sticker (see attached).

I had a second out drive for the boat (upper and lower) but it was stolen.

Thanks for all the advice. I'll use the insurance replacement cost money to buy a 1.5.

 

[jbutler67]

Attached picture this time. Sticker is tough to read but it has
1.32 822756

 

[Scott Danforth]

boat that big should have a big block in it

 

[jbutler67]

Engine is Mercruiser with s/n M048938.

Is that a 5.0 or 5.7L?

 

[Scott Danforth]

comes back as 1998 5.7

still a bit small in a 24' boat

 

[achris]

24ft is fine with a 5.7, provided it's not over-propped... If you're ocean-going you don't need 60knots... 1.5:1 should be ok, but I would also consider 1.62 to get you into a bigger prop (more pitch)...

Your engine, 0M048938, is a 5.7L, FWC, Alpha. That's a 250 propshaft horsepower, 5.7 litre engine with a 2bbl carb. Max revs are specced at 4400-4800. Regardless of the drive ratio you choose, I would prop right to the very top of that range (a hundred over is not a problem)... That will make the boat as 'driveable' as possible, and not lug the engine...

Chris......

 

[jbutler67]

Thank you both Scott and Chris. This forum is extremely helpful.

 

[Scott Danforth]

Hey achris , not 100% sure, however the upper may not work anyway. the OP has a 1998 motor, which would have been an Alpha 2 drive

however i dont believe the 1.32:1 was available in an alpha 2, and if I remember, the 1.32:1 was an Alpha 1 or MR drive only. there was a similar discussion a week ago.

 

[Walt T]

It's possible the gear ratio may have been changed in that drive and it no longer has the 1.32s. Pop the top cap and count the teeth.Take all of 10 minutes.

 

[kenny nunez]

The first time the 1.32 was used was in 76 on the 233 Ford 351 package. It took some of the strain off of the pre Alpha lower gear sets. The early 260 packages with 1.5 gear set pre Alpha were tearing up the lowers because of the way the pinion was pre loaded. I was replacing lowers under warranty so often that I memorized the part # for the lower. If Mercruiser would not warrant the repair I would tell the customer to call their insurance company. 1623-5356 A. if my memory is right.

 

[achris]

The first time the 1.32 was used was in 76 on the 233 Ford 351 package. It took some of the strain off of the pre Alpha lower gear sets. The early 260 packages with 1.5 gear set pre Alpha were tearing up the lowers because of the way the pinion was pre loaded. I was replacing lowers under warranty so often that I memorized the part # for the lower. If Mercruiser would not warrant the repair I would tell the customer to call their insurance company. 1623-5356 A. if my memory is right.

kenny nunez Kenny, please explain to us when the 'pre Alpha' was released and what it looked like. I have checked all the Merc documentation I have and can't find it. Is this a special drive they produced?

Chris...

https://forums.iboats.com/forum/engi...alpha’-drive

Hey achris , not 100% sure, however the upper may not work anyway. the OP has a 1998 motor, which would have been an Alpha 2 drive

however i dont believe the 1.32:1 was available in an alpha 2, and if I remember, the 1.32:1 was an Alpha 1 or MR drive only. there was a similar discussion a week ago.

Quite right Scott Danforth However, the gears from 1966 to 1997 are all the same so, in theory, someone could have put a 1.32 gear set into a Gen II housing.. In 98 the casting for the upper housing was changed slightly and the older gear sets no longer fitted...
The problem with that theory is that the decal stamp appears to be factory, and the Gen II was never supplied with a 1.32 gear set from the factory... Which brings me to that decal. It doesn't look like a Gen II decal. It looks 'MR'. It is possible someone has dropped a 1998 engine in front of an 'MR' gimbal and drive, or someones done a hatchet job on a Gen II gimbal housing and somehow fitted an older 'MR' drive to a Gen II bell housing...

I wonder if there's a chance the OP could post a picture of the complete drive and gimbal housing?

Chris....

 

[fishrdan]

Ayuh,...... It'll be a Dog with that ratio,.....

The 1.32s are very rare,..... I'm surprised you found one still serviceable,...... the gear sets are NLA,....

Wasn't someone looking for one of those drives a week or two ago................