Swapping Mercruiser drives work?

[Eric 3.7LX Alpha 1]

Hey guys,
Posted couple months ago bout my my lower prop shaft seals leaking from wire fishing line getting wrapped on it. Replaced seals but shaft was NG. Had a friend offer a older Mercruiser one drive if it would fit. It has the preload pin and lift ring on the top cover.

Put a new impeller kit in it an bolted it up. Went out and I am getting a whine from the drive in either gear not much in neutral which I never got with my alpha lower. Only used it 1 trip and putted around the ramp. I got the top cover off my Alpha and my bearing under the cover was rusted and looked like crap. Think this is my whine. Now I am considering using his compete drive, upper as well but the ratio is different. Gear count is 24/24 in his upper. Stamped HP 165, I think it is a 1.65 ratio but not positive, I have the 1.84 ratio. I am not looking for a speed monster, never even pushed it to WOT maybe 3200-3400 RPM's tops, but looking to get by for the remaining year and get a new complete SEI drive this winter.

It has been a tough year for maintenance on the boat replaced the lower shift cable, all bellows, gimbal bearing, converted charging from stator/voltage regulator to Delco marine alternator (made my own brackets), and did water pump/speedi sleeve repair on engine. So would like to hold off on another grand or so till winter. How will the difference in gearing effect the RPM and would it be tolerable to get around? Is there any other problems I might encounter with this swap?

Thanks for the replies and patience in reading this book!!!

 

[nola mike]

Re: Swapping Mercruiser drives work?

yeah, you should be able to get by with that setup, but you'll need to downsize your prop. i used this site to run some rough numbers on my boat, which originally had a 1.84 with a 21 pitch prop and topped out at about 50mph/4600 rpm WOT. if i switched to a 1.65, i'd need a 19p to run the same WOT rpms. obviously, ymmv depending on your current setup...

 

[Eric 3.7LX Alpha 1]

Re: Swapping Mercruiser drives work?

Thanks for the reply, gonna give it a try and see how it feels. I'm not a speed junkie so it might be ok for the year.

I do have a couple of fishing spots off Martha's Vineyard so that will be the test. I'd rather be be trolling around pulling a tube n worm.

 

[nola mike]

Re: Swapping Mercruiser drives work?

Thanks for the reply, gonna give it a try and see how it feels. I'm not a speed junkie so it might be ok for the year.

I do have a couple of fishing spots off Martha's Vineyard so that will be the test. I'd rather be be trolling around pulling a tube n worm.

not a question of being a speed junkie--you'll have a real hard time getting out of the hole, and being over-propped is hard on the engine. i probably have a prop for you if you need it, send me a PM in the future. hell, you could borrow it from me if you want.

Edgartown/chappaquiddick was my old stomping ground. have a pint at the wharf for me...or a mudslide at david ryan's.