Alpha Drives, Preload Pins, Lower Units
07-21-2004, 04:49 PM
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Alpha Drives, Preload Pins, Lower Units
Hello, and thanks in advance for the expert advise. I have a 1983 Formula 17' with MerCruiser outdrive. The outdrive has a square top bearing cap (no loophole), so I think it is an “Alpha”, but not sure. I think there was a transition period where they are called “I” or "R" drives or something. Not sure. Anyway, I am removing the factory 4.3L V6 and installing a modified 5.7L V8. I think the outdrive will be OK if I change the ratio to 1:5 to 1 like most other V8’s, but I have been hearing that the lower unit of my drive is a weaker design than the later version of Alpha 1, Gen 1. I believe mine has the driveshaft preload pin, and a late Alpha 1, Gen 1 lower unit without the driveshaft preload pin is stronger? Will these two lower units exchange? Since I need to change my upper gear ratio anyway, maybe I should be interested in exchanging the entire outdrive for a late model Alpha 1, Gen 1 outdrive.
Your advice is appreciated. If anybody has access to a 1:50 to 1 Alpha 1 Gen 1 I'd be interested. Thank you again.
Clint
Your advice is appreciated. If anybody has access to a 1:50 to 1 Alpha 1 Gen 1 I'd be interested. Thank you again.
Clint
07-21-2004, 06:59 PM
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Re: Alpha Drives, Preload Pins, Lower Units
What was known as an "I" drive, was the early model, with the lift eye on top, and 6 bolts (studs) to the bell housing. "R", and "MR" models were after the "I", and before the "Alpha". You can exchange the complete drive. I believe some of the earlier "R/MR" models with the preload pin were necked down along the shaft and others weren't, but don't hold me to that. I had a 1975 18' Formula that originally had an inline 6, and I converted it to a 260 (350 V8) Mercruiser, and kept the "I" drive (1.65 ratio) on it. I just bumped the pitch of the prop up higher.
07-21-2004, 08:01 PM
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Re: Alpha Drives, Preload Pins, Lower Units
The Alpha One lower vertical shaft is much larger in diameter than your MR drive and is quite a bit stronger. Since you need to change your gear ratio anyway, I'd just upgrade to a complete Gen 1 Alpha drive.
Good luck,
Kurt.
Good luck,
Kurt.
07-22-2004, 05:27 AM
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Re: Alpha Drives, Preload Pins, Lower Units
Like Biggus said, swap the whole drive for a Gen1.
When I was searching for parts to replace the water pump in my Alpha Gen1 I found that parts from the earlier versions aren't compatible with later models.
Don't even think about going with a Gen II, it won't bolt up to your gimbal assembly. Won't bolt up to a Gen1 either.
When I was searching for parts to replace the water pump in my Alpha Gen1 I found that parts from the earlier versions aren't compatible with later models.
Don't even think about going with a Gen II, it won't bolt up to your gimbal assembly. Won't bolt up to a Gen1 either.
