Replacing a powerhead

[towtruk7]

Just wondering if any of you have ever changed a power head? I have a 50 horse Johnson that has diddly for compression in one cylinder. The lower is in decent shape so I would prefer not to change the whole motor out unless necessary. Mr. Goodwrench has nothing to worry about with me but I am somewhat handy. Any suggestions or should I get off my cheap butt and find a decent used motor?

[BIG DS]

I would bet if you pulled the head off of the motor you would find that the cylinder with the low compression is scored and will need to be honed, new piston and rings. Check into the parts needed to complete the job and compare that with purchasing a used motor. Keep in mind that if you fix the motor you have, you'll know what you have. If you by a used motor you could be buying someone elses nightmare. A reputable dealer should be able to hook you up with a quality motor with an inspection and repair sheet on the motor. They would probably even give you something on trade for your old motor.

[musky hunter]

Find a nearby marine or small engine shop, bring the engine block to them, and have them hone or rebore the bad cylinders. Honing is cheaper than reboring, it depends on how deep the scoring is. Then buy an ovesize piston(s). The oversize amount is very small, the shop will know which size to order. It's a good deal of work, probably a couple of weekends but an older 50 is a simple engine. They can also order all the gaskets that you'll need. They have on line sources for a whole array of small engine parts. Get pricing in advance of ordering any work.

Finding a used powerhead may also be an option if you can find one that has a banged up lower unit, but it's like finding a needle in a haystack. But if you find one, it would be relatively easy to swap power heads out, maybe only one weekend of work.

By reboring, you have a partially rebuilt engine, depending on how many bearings, etc. you decide to replace and you'll know for certain what you have.

But whatever route you decide, go to the library and check out a repair manual, it will show step by step what needs to be done.

I've done this both ways it's a great project if you like to tinker and a lousy project if you'd rather be fishing.

[BIG DS]

Good point! If it is something that you do want to do, make sure and replace the crankshaft seals. Even if they don't look bad, do it. It would be a good idea also to take the carbs to a shop and have them cleaned and such while the motor is torn down. Used powerheads are near impossible to find. I have just recently tried and ended up doing the rebuild thing.

[towtruk7]

Thanks for the info guys, I really appreciate it. I have talked to two shops and basically got the same answer from them - it's too old to put that much money into. The plan was to pick up a used motor until I could afford something more but then I found a powerhead on hsolist that I thought I could take a chance on. Maybe I should just pull out the father's day card and see if I can sneak a new boat past the mrs. Once again, thanks for the input.

[Valv]

Towtruk, beware if you buy on hsolist not to get saltwater motors, they are junk, even if 2 years old...

These 2 cylinders OMC powerheads were very popular for amny years, you won't have much trouble finding a good used one.

In fact if you email me I can keep one eye out for you (I had one 2 weeks ago from a '96...)