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New to me boat/ In search of OMC stuff


skinny
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just got me a 18’alum and trailer still digging at it  motor I think is making noise kind of rattle I thought it was in front of motor pulled timing cover thinking maybe wore chain it’s gear to gear 

this was good buy but not so if can’t get her going 
 

 

My go to for boat repair parts has retired and shut down 

im looking for omc 4cyl 120 (possibly complete)

at very least I currently need vaLve cover gasket timing cover gasket and still trying to figure out noise 

also engine trim motor 

it has a electric shift stinger so could be interested in one to

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4 hours ago, misfish said:

Nice boat . To bad about the issue . Out board would be a drop and swap.

Agreed, it is sharp. And I’d do the same. Close the hole, replace the transom, add a knee brace and splashwell. But over the long run. Winter project. 
 

I’d try to get it running and use it for the rest of the season if it didn’t cost an arm and a leg. 

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Ya, what Hack said,  lot easier working on something standing upright than upside down in the hull in confined space.   Friend of mine had an inboard and even being a certified mechanic said never again would he go for an inboard.

Does it actually start and run or just make funny noises.

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It starts and runs 

but it has a bit of noise thought in the front of motor like a loose timing chain 

removed cover to find gear to gear no chain 

so hopefully I can find gasket tomorrow to close it up 

might try running with front mount off see if the sound is in mount 

 

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4cyl 

gm2.5 

catch is they used it a bunch of years but then made changes  I’ve been trying to figure out the last year and model so it easier to get gaskets and bits 

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1 hour ago, OhioFisherman said:

Most of those inboards are based around an automotive engine, my searay had a 351 ford cleveland motor (mercruiser), some of those used 4 cylinder gm or ford motors.

True but weren’t they purposely built for marine? Automotive engines don’t have to work as hard ie under continual load wide open?

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16 hours ago, Hack_Fisherman said:

True but weren’t they purposely built for marine? Automotive engines don’t have to work as hard ie under continual load wide open?

Hack, I believe the basic engines were the same, just adapted for marine use. Marine engines don't usually have to deal with the dust and dirt a car engine does.

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True they don’t. But aside from reverse running engines (on a twin screw vessel) I think there was more to it. I recall stories of guys pulling 428’s from old Chris Craft’s and finding the couldn’t cool them enough for street use. This could be a total tale with no truth of course... 
 

But I keep going back to questioning car vs a boat differences. 
did they throw beefier cranks, rods and pistons in the marine block? Different cams for different power bands? A car uses a lot of torque and HP to get moving, then considerably less once momentum is gained, hills fade etc., whereas a boat needs continual power all the time except trolling. Or we’re all short blocks of the era simply robust enough to handle either ?

Edited by Hack_Fisherman
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On 8/3/2021 at 5:29 PM, Hack_Fisherman said:

True they don’t. But aside from reverse running engines (on a twin screw vessel) I think there was more to it. I recall stories of guys pulling 428’s from old Chris Craft’s and finding the couldn’t cool them enough for street use. This could be a total tale with no truth of course... 
 

But I keep going back to questioning car vs a boat differences. 
did they throw beefier cranks, rods and pistons in the marine block? Different cams for different power bands? A car uses a lot of torque and HP to get moving, then considerably less once momentum is gained, hills fade etc., whereas a boat needs continual power all the time except trolling. Or we’re all short blocks of the era simply robust enough to handle either ?

Hack, with a marine engine you normally  have an unlimited  source of cool water for cooling, Years ago a lot of the short haul tractors I drove were gas engines, like a 460 cubic inch in Fords and a 440 cubic inch in Dodges. There were differences in the number of cooling passages in the block and heads because the truck engines operated under a heavier load, even though they probably had a bigger radiator too.

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I know the 2.5 automotive and the 2.5 marine are internally different. Not sure what these differences are; but you cannot switch them from automotive to marine; not without modifications made. I could ask my nephew (Marine mechanic) why; I just don't remember.

Dan.   

Edited by DanD
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OMC went out of business over 20 years ago - in December, 2000.

Even if you can find parts, you're better off to junk the old engine and replace it with an outboard on a bracket. It will work 100x better, use way less fuel, and just be fewer headaches all the way round.

   
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On 8/9/2021 at 11:06 AM, craigdritchie said:

OMC went out of business over 20 years ago - in December, 2000.

Even if you can find parts, you're better off to junk the old engine and replace it with an outboard on a bracket. It will work 100x better, use way less fuel, and just be fewer headaches all the way round.

   

Later season use and less winterizing work. 
 

bracket is even better than a splashwell conversion. More floor space, but not everyone can build one
 

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  • 2 weeks later...

Camshafts are different On Marine engines to prevent cooling water being sucked into the engine from the manifolds.  Those old OMC outdrives are really hard to get parts for.  And the transom hole won’t  be the same size as a new Merc Alpha drive. So your options are limited unfortunately. 

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21 hours ago, Canuck said:

Camshafts are different On Marine engines to prevent cooling water being sucked into the engine from the manifolds.  Those old OMC outdrives are really hard to get parts for.  And the transom hole won’t  be the same size as a new Merc Alpha drive. So your options are limited unfortunately. 

Outboard conversion sounds like the only practical option

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Ok so I had the original motor running but made noise 

couldn’t find the noise after looking a bunch and had others look  did compression test and got 0 on #3 

 

decided to look for motor after checking out some leads to seized motors I decided to pull the head on mine

thats when I found a missing valve and piston on #3 

at that point I located another unsized motor and drive but 1.5 hours away went and got it all 

pulled intake to use the one I had and found a bad crack repair 

good thing my brother can weld cast 

so now at this point second motor is in boat and runs now dealing with getting drive on 

so that’s the story and keep all posted 

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