Re: 1985 Johnson 50hp needs piston rebuilt
IMO, I'd keep it and rebuild it if you have the time and money. I'm about $1200 into rebuilding a 3cyl 60hp myself, and $330 of that is buying it. I have about $300 more in parts that I need to get it all done. Here is what I would do if you are interested in doing it.
1st: Buy a factory service manual. It will help a ton and really helps find all the little in's and out's of getting it apart and back together again.
I have done my entire rebuild with justy basic tools so far, and the only special tool I had to buy was a harmonic balancer puller from a local auto parts store so I could pull the flywheel. You will need one as well unless you already have one. Everything else I have done myself, except the machine work boring/honing cylinders. I had to have 1 bored over and the other 2 just honed. Funny thing is, someone had already worked on the engine before and bored the 2 I'm leaving alone yet not touched the 1 I had to have bored over. At least now they will all be the same bore. I spent $100 on machine shop labor, everything else has been parts for the engine. And honestly, I can count $200 at least that I had to replace because the engine had been neglected for too long. Here is a basic list of parts you will be wanting, and/or things you will probably want to do while yo have it apart anyways.
Carb rebuilds: Just do them while you have it apart. Good chance they might be clogged anyways. about $35/kit. You would need 2 I believe, since it's a 2cyl.
Water Pump kit: You might be able to just replace the impeller, but for $75 you can buy the entire kit, which has the housing, impeller, plate, etc. Mine was trashed.
Change lower unit gear lube while you are at it and if possible, pressure test the lower unit. You can build your own tool for this for $20. It's a bicycle pump with air guage, and a lower unit oil pump/hose. You use the fitting from the hose and attach it to the bicycle pump, then pump 10psi into the lower unit. From my uderstanding, if it holds 10psi for an hour it's good. If not, submerge it in water and look for the leak, whick will be known by the air bubbles coming out of it.
And of course engine parts. That will depend on how much you want to spend and how bad the cylinders are. If the 2nd cylinder is out of round or out of spec, it will need to be bored as well. The shop charged $35 for boring, $25 for honing, per cylinder. I am replacing everything except the pistons/rods in all 3 cylinders. Top cylinder (the one I had bored) is getting new piston, rings, and all bearings. Bottom 2 cylinders are getting new rings and all bearings. Also getting new crank bearings, powerhead gasket set, main crank seal/bearing (forgot the tech term for it). I just built a motor stand for it to sit on (instructions for that can be found on iboats), and have done all the work from there. I just picked up the powerhead once I had it unbolted, it wasn't terrible heavy with all the carbs off, flywheel off, electrical off, etc. Just down to the basic block.
Hope that helps a little. Do some pricing out of parts and get a feel for what it's going to cost, then decide from there. Worst case I'd tear it down, learn a lot about how to do it, and if it's too much $$$ to spend to fix it, part it out. You will get more $$$ if you do it yourself opposed to selling it as a whole, and the knowledge you will learn from doing it will be priceless.
