Re-engine 1993 Sea Ray Overnighter?

J

Joe Gannon

New Member
Nov 15, 2021
2
Boat Info
240 OV 1993
Engines
7.4 Mercruiser B1
I would be greatful for any tips, leads, warnings, encouragement etc on a project to replace the 7.4L Mercruiser/Bravo1 on a 1993 Sea Ray "OV" overnighter, with a 2004 Mercruiser 350 MPI engine (about 400 hrs runs great). My local marina was unsure of how much work was involved. I imagine the engine mounts would be very different and maybe it's much harder to line up a non-standard engine than I imagine.
 
Haven't done it but this sounds like a really bad idea. It is tight and unpleasant working in the engine compartment of an I/O. Fix it or replace it with an exact match, in the opinion of this hobbyist.
 
I guess my question Joe is why are you replacing the current engine if it only has 400hrs and runs great? Are you just looking to go with a bigger engine?
 
A 7.4 is a big block while a 350 is a small block. Maybe the auto speed shops have adapter mounts but ...... can't hurt to check.
 
Christo, he is getting a 350 with 400 hours. Hasnt said what is wrong with the 7.4. I would opt for rebuilding the 7.4 but maybe he is getting the 350 free.
 
Pirate Lady said:
Christo, he is getting a 350 with 400 hours. Hasnt said what is wrong with the 7.4. I would opt for rebuilding the 7.4 but maybe he is getting the 350 free.
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Oh duh! Makes sense, didn’t read that right Pirate lol
 
I went the other way in a pick up once. The only thing that had to be changed was bigger exhaust and a different power steering pump. Everything else was a direct match.
In Mercruiser world, assuming the flywheels are the same diameter, bet it is similar assuming it's a complete drop in. Does the 350 come with the flywheel and housing?
 
Shenanigans77 said:
A BBC and SBC block mount locations are identical.
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Engine mounts for the two are different. Swapping a BBC for a SBC or vice versa is easy. The space issue is another matter entirely.
This tells me he should go elsewhere if he actually does want to do it: "My local marina was unsure of how much work was involved."
 
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Beyond the engine, the entire out drive and prop set likely needs to be changed. Torque output between the 2 are very different. That will require changing the gear ratio.
 
I doubt the ratios will be a problem with a 350 in front of a Bravo. More of a concern with the Alpha.
 
Thornton69 said:
I doubt the ratios will be a problem with a 350 in front of a Bravo. More of a concern with the Alpha.
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I think I've been talked out of it. I've been slow to understand how much torque plays a role and how the 350 MPI would really struggle to get the boat moving, unless I got it wrong. Appreciate the many thoughtful comments here. I really like what I understand about Sea Rays so far (good thing since I just bought one) and impressed by build-quality, seems like a "step up" from others.
 
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