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OMC 25 to Mercruiser 30

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dhog

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I have a good 1983 OMC 2.5 tha

I have a good 1983 OMC 2.5 that I would like to install in my 1994 Bayliner 1850 Capri. I have the 3.0 engine (bad) from the 94 Bayliner except for head/intake exhaust and was wondering what problems I might run into. Also what is the difference in HP from the 2.5 to the 3.0? Thanks for your help.
 
"The compression checks good o

"The compression checks good on the 2.5 so I'm convinced to use this GM block with components from the 3.0- starter,alternator,exhaust/intake manifold,bellhousing,engine coupler,and etc...."
 
"you'll lose 20HP and the

"you'll lose 20HP and the coupler won't work as the crankshaft bolt pattern on the 1983 engine is different. You would need to source an old style Merc coupler....not sure how that will work with your Gen II Alpha drive, but I *think* it should be ok. Other than that all the 3.0 stuff should pretty much bolt on to the 2.5 just fine.
Without the 3.0 exhaust you might have to get creative with flexible marine exhaust hose to get it to line up with the downpipe of your Merc drive system"
 
"Thanks Hy Stat, I actually ha

"Thanks Hy Stat, I actually have removed the flywheel and engine coupler from the 3.0 and installed onto the 2.5 (simply unbolted OMC coupler). I purchased a intake/exhaust manifold and carb from 1989 3.0 I have the rocker arm (valve) cover, distributor, exhaust riser,and coil as well as the front engine mount from the 3.0 so my hope everything else will work. Thanks again for the help!!!"
 
"1994 and 1983 should have dif

"1994 and 1983 should have different crankshafts, so one or the other other of your engine's year must be wrong, but that's great.
Before you install the front mount, tie-wrap a spare alternator belt in there so if you ever have to replace it, you won't have to remove the engine mount."
 
"If I got a 1987 2.5L chev OMC

"If I got a 1987 2.5L chev OMC block, can I take all the internals from a 1987 3.0 litre OMC chev. engine and use them in the 2.5 litre block? What I need is a block for a 1987 3.0litre and I can't find one. If someone knows of one please call me at 780 808-1789. I am traveling to Oregon this weekend and would sure like to find a block. }"
 
"no - blocks are different, bu

"no - blocks are different, but your search is still vast - you can use any Mercruiser or OMC 3.0 or "140" from about 1966 to about 1988. After 88 or 89 , they changed the rear bolt pattern on the crank. good luck...I'm still pissed my 3.0 block sold on ebay last year for $50... where were all you people then?
"
 
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