1969 Mercrusier 120 rebuild... Worth the money?

[FishingTheFL]

Replaced exhaust elbow, head gasket, rebuilt carb, hydraulic lifters, exhaust gaskets and manifolds.... Now it needs a can shaft... I got a ton of money into it... Is it worth spending another $250+ gaskets and timing gear and what ever else... I hate to spend all this money to have the motor blow because mechanic is leading me on saying " this will get you out there"... Basically crank shaft, piston head and rods, rings... Are what remains.... So much for fishing this year

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[geezer]

Boy...that's a tough call. If it were just the $250 without the rest it would an easy decision. Just wonder why the cam issue was missed when the mechanic was all over the engine. Might he be willing to guarantee For x number of hours? Seems like you must already have paid a lot. I have a '73 120 that's good but I wonder how much longer the out drive is gonna last. Your already at the end of the season, might want a consider an off season beat up boat with a good 130/140 and newer out drive,

[FishingTheFL]

Exhaust elbow was $250 + $125 for exhaust manifold gasket and head gasket. Rebuild the out drive already... That was around $200... Now camshaft is $255 plus the timing gear which idk the price of that yet plus the install... That's another $400 with no grantees on work other then I been watching what he is doing and he is explaining it as he goes... Do I have to worry about the crank and pistons being wore down and need replacing? If so does that mean the block is probably worn out also?

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[fisherdude]

compression test should tell what shape the motors in 

[FishingTheFL]

It will show bad compression with a bad cam correct? That's why we didn't do a compression test.

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[Shellback]

A bad cam is usually the result of the surface hardening wearing off. Once past the hardening, the lobes wear off very fast. Been quite a few years now, but I remember replacing a number of cams in small block Chevy's. Not sure on a compression check. What could happen is if the intake valve cam lobe is bad, the cylinder might not get the air in it to build compression. I guess it depends on what lobes are worn off. Wouldn't hurt to try a compression check. If it's good, I wouldn't hesitate to put a cam in it. You could pull the valve cover off and see what valves are affected by the bad cam. If you aren't getting any lift on the intake valve, then the compression check isn't going to tell you much.

[FishingTheFL]

2nd cylinder wasn't getting the lift like the other ones and that is also where the head gasket was blown out. I was thinking that maybe the cylinder would be worn from weak compression but idk anything about motors. We already have the cam all the way out.

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[Xxx]

I for the life of me can't understand that any mechanic would pull the head and put lifters in and a used cam shaft, that's like changing the oil and just wiping the filter clean on the outside. Most cams I ever put in the lifters and cam are a set but paid for individually. Now you need another head gasket, when the heads off check the ridge, this is where the piston stops at the top see if you feel like a ledge at the top, basically the cylinder is wore, there shouldn't be a ledge at the top of the cylinder, check all the cylinders for a bump at the top. If so pull a few rod bearings for wear, should look the same in the middle of the bearing as the sides if you can see brass other then a even grey colors I'd pull the whole works apart and do it right, if you think it's worth the boat. I'd trust a rebuild before a used motor might go through all that work and $$$ and have the same or worse than what you already have. Best of luck to ya!! PS the ridge in the cylinder is tolerable up to just that you can feel it, as there could some carbon deposits there also.

Edited September 6, 2016 by pap

[FishingTheFL]

The boat its self is solid. Old Aluminum. Just needs a new floor and paint. No leaks. We ordered a new cam and timing gear... Can't believe a fiber glass gear is $100... Cam is $255... Head gasket is brand new. I think he checked the heads when we changed the head gasket. I'll make sure today

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[cyrility]

Don't use the fiber gear. You can get a metal one. Little noisy but lasts forever. May need to modify oiler. Check the internet.

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[W.W.IV.]

I for the life of me can't understand that any mechanic would pull the head and put lifters in and a used cam shaft, that's like changing the oil and just wiping the filter clean on the outside. Most cams I ever put in the lifters and cam are a set but paid for individually. Now you need another head gasket, when the heads off check the ridge, this is where the piston stops at the top see if you feel like a ledge at the top, basically the cylinder is wore, there shouldn't be a ledge at the top of the cylinder, check all the cylinders for a bump at the top. If so pull a few rod bearings for wear, should look the same in the middle of the bearing as the sides if you can see brass other then a even grey colors I'd pull the whole works apart and do it right, if you think it's worth the boat. I'd trust a rebuild before a used motor might go through all that work and $$$ and have the same or worse than what you already have. Best of luck to ya!! PS the ridge in the cylinder is tolerable up to just that you can feel it, as there could some carbon deposits there also.

I'm thinking Pap is right about a complete rebuild,the top of the cylinder bore on a motor that old most likely will have a good ridge from ring wear. Before you spend more $$$ you will have to pull the pistons and check the cylinder bores for out of round and tapper. if either is to bad you will not be able to clean up the bores with a hone. that means that you will have to have the block bored out over size and go for over size rings and pistons, thats getting into some big bucks. A short Block would have been the way to go, if you could even find one. Thats something to think about. Lots of luck.  Mike.

Edited September 7, 2016 by W.W.IV.

[FishingTheFL]

Sounds like I just better start saving to put a different motor in it or switch it to an outboard so I can get some winter use out of it

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[rolmops]

It should not be too hard to pull that block and stick a second hand 140 block in there. You can winter fish all you want with an I/O as long as you drain the block when you get out of the water.

Edited September 7, 2016 by rolmops