Alpha 1 bent prop shaft
 

I was swapping out my 4.3 for a 5.7 and noticed that the prop shaft on my Alpha 1 (gen 1 I think...1993) had a slight wobble. I put a dial indicator on it and found out it is about .006 out. I assume this will be a problem with vibrations and worn out seals. Am I correct in my assumptions?

Also I am picking up another outdrive for parts (Alpha 1, v-8 early 80's I believe) will the prop shaft from this one fit in the other? Or...should I just replace the bad outdrive with the v-8 outdrive?

One last consideration...in doing this swap, I believe the v-6 outdrives have a different gear ratio than v-8 outdrives. If I stay with the original outdrive, can I prop up for more top end speed with the v-6/5.7 combo?

Many roads, which one to follow.

Much thanks!

I'm surprised you noticed a wobble of .006. You are correct a bent shaft is bad. I think .006 in a small one. I didn't check for sure but I would think the prop shafts from genI to genII are different. Little if anything else is interchangeable. I won't invest in a used genI. It is possible to prop the 4.3 gears to work. Whether or not it is ideal I can't say.

Alpha
 

:cool-smiley-027:
It's an Alpha One, Gen II if it's '93

:cool-smiley-027:
'93 and '84+ Lowers are the same part number. The prop shafts are both 44-824110. If it's earlier than that, it's probably better to look for newer "old" stock.:D

MR/ALPHA ONE - GEN I (Up to 1990)
OEM RATIO ENGINE
5-01471017 1.47 (20/22) MOST V8
5-01622017 1.62 (24/24) 6 Cyl. INLINE
5-01811017 1.81 (17/19) V6 & 470/485
5-01941017 1.94 (20/24) 4 Cyl. INLINE
5-01301017 1.30 (16/20) V8

ALPHA ONE - GEN II (1991 and Newer)
OEM RATIO ENGINE
5-5010150GP 1.47 (20/22) 5.0LEFI/5.7L/350
5-5010165GP 1.62 (24/24) 4.3LH/4.3LEFI/5.0
5-5010184GP 1.81 (17/19) 4.3L/4.3LX
5-5010198GP 1.94 (20/24) 3.0L/3.0LX

Sorry, Thats what I get for not checking before I responded. As stated above they are the same.

I have friend who did a very similar swap. Initially, he ran a 1.50 ratio V8 outdrive. He then later reverted back to the original outdrive from the 4.3. With the original drive, and a larger pitch prop, He found a gain of 3 mph. The only trade off we could see, would be the additional torque applied to the lower unit itself.

Thanks guys! Took it to the local mercruiser mech. Said run it like it is. Also pointed out a very small crack in the stainless prop (14x21). I will shoot with the 21 prop but think I will move up to a 23. I plan to switch the stock 1.81 gears to 1.47 and might have the prop shaft changed while it's in. How difficult is it to change the uppers? I know the better they are shimmed, the longer it will last. I started with a stock 350 and then got bit by the more bug...now I'm plan to stuff a 383 stroker in there. Keeping it less than 400 horses for now...maybe switch to bravo later. Who ever heard of a 21' Sea Ray BR with a 383 and bravo? I almost feel like I am getting in over my head.