Alpha 1 bent prop shaft

[jshughes808]

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!

[MOBILEMERCMAN]

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.

[nwimbush]

Originally Posted by jshughes808

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.!

It's an Alpha One, Gen II if it's '93

Originally Posted by jshughes808

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? !

'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.

Originally Posted by jshughes808

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?

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

[MOBILEMERCMAN]

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

[spazboz]

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.

[jshughes808]

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.