165/165 to 170/165 Alpha One repower

Hello all, I have been searching but can't find what I am looking for. We are re-powering a 77 Grady from 165 straight 6 to the 3.7 170. We have only one gimbal housing, for the original 165, but we have 2 outdrives...the original 165 and the one that came with the 3.7 engine which is an alpha one series I. Which one should we use?

I can only make out 1.84R on the Alpha, no numbers on the original outdrive. It looks like the shafts are a different length? We also just have the one inner plate that bolts to the transom with the original pump/steering, etc.

What is our best setup?

Re: 165/165 to 170/165 Alpha One repower

You are replacing the solid straight 6 with a problematic 470 4 cyl?

Re: 165/165 to 170/165 Alpha One repower

I agree with cr2k. I own twin 3.7 470's and wish i had something else, but i got what i bought (new to boating and didnt really do my research) I am forging ahead with no major problems but these motors require more than a novice mechanics attention. Whereas that straight six (even if you have to rebuild it) should be alot less of a headache. Sell the 3.7 for parts or whole and fix your six. Side note the 3.7 is worth quite a bit in parts or whole(depending on what you paid for it)if it is a good motor. I know because my local used marine parts store kills me on my 3.7 parts.

Re: 165/165 to 170/165 Alpha One repower

artificialreef said:

I agree with cr2k. I own twin 3.7 470's and wish i had something else, but i got what i bought (new to boating and didnt really do my research) I am forging ahead with no major problems but these motors require more than a novice mechanics attention. Whereas that straight six (even if you have to rebuild it) should be alot less of a headache. Sell the 3.7 for parts or whole and fix your six. Side note the 3.7 is worth quite a bit in parts or whole(depending on what you paid for it)if it is a good motor. I know because my local used marine parts store kills me on my 3.7 parts.

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Same here. Made a trip thinking we were getting a 6, turned out a 4. I have read the issues and am not scared. I am a seasoned mechanic. We have 2 alternators laying around from the 6 and will be installing one. Other than that it's just like every other boat engine. We aren't running for speed, just to get out fishing. It was rebuilt last season.

The 6 was seized solid, had to beat it apart with hammers, 2 cracks in the block, manifold welded, etc. It was junk. We are better off than we were before. And I like the 4, like a miniature tug engine. I used to work in the shipyards.

Semantics aside, anyone know which will be the better outdrive to use?

Re: 165/165 to 170/165 Alpha One repower

If the drives are geared different, use the one that came with the 470. I happened to enjoy my 470 but I am an aircraft mechanic by trade. I happened to LOVE the 470 when I sold it though.

Re: 165/165 to 170/165 Alpha One repower

Thanks for the help. I just wanted to make sure they were both compatible as it looks like one has a longer shaft.

BTW, our "rebuilt" engine was not so much "rebuilt". Never trust Craigslist. Looks like someone dumped a quart of sand in it and a gallon of rust. Here we go again...

Re: 165/165 to 170/165 Alpha One repower

Frank and Beans said:

Thanks for the help. I just wanted to make sure they were both compatible as it looks like one has a longer shaft.

BTW, our "rebuilt" engine was not so much "rebuilt". Never trust Craigslist. Looks like someone dumped a quart of sand in it and a gallon of rust. Here we go again...

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Ayuh,.... the GM In-line motors, when used with the MC-1 transom assembly, 'n the MC-1 drive, use the short input shaft....

So,... Dependin' on what parts yer startin' with,... Determines whether ya need the short shaft, or the longer shaft...
They can Not be used in the wrong transom assembly....

If ya use the short shaft, where it should be long,... The coupler will rip out, in No time....
Of course, if ya use the long shaft in a short shaft application, it won't go all the way together...

Re: 165/165 to 170/165 Alpha One repower

go with a 4.3 or find a nice 292 and use the marine exhaust, distributors, etc. from your 250 (the 165hp)