starting rebuild on '94 Evinrude 175hp

[awthacker]

So the powerhead is finally torn down completely and I'm gonna try and put it back together. No internal damage, it just rusted up inside and froze up. To me, it looked like the wrists of the piston arms were what was so seized up that the crankshaft wouldn't turn. Four of the six piston arms were completely frozen. Four of the pistons also had to be pounded out with a hammer, two moved freely. The bearings where the piston arm connects to the crankshaft were all in pretty good shape already.

I've disassembled, cleaned, and reassembled each piston. The last piston was missing a bearing. I can buy the bearing and retainer set for $18 plus shipping, but does anyone have just one bearing like the one missing in the picture?

I'm gonna start cleaning the block this week and would like to get the crankshaft and pistons back in place. I'll post some pictures and questions as I go. I'm not 100% sure how the saltwater got into the cylinders, but I'll post some suspicious pictures and maybe you guys have some ideas. For now, here is the pictures of the piston arm, cleaned and ready for reassembly, less one bearing.

 

[smokeonthewater]

These parts need to have precise tolerances.... You are gonna need a machine shop to measure and surface these parts for you and likely ALL of the bearings should be replaced including the bearings between the crank and block.

Just take the block, crank, rods, and pistons with you to the machine shop and have it all checked out. Get info from them on what needs to be done and what you need. IE oversize pistons, turned crank, etc.

Just slapping it back together is a recipe for an engine that throws a rod (doing much more damage) in the first week and leaves you stranded.

 

[awthacker]

So do you think that the disassambly process is all I can really do myself, and I should now turn it over to the pros?

My goal was to tear it down, learn how it worked, clean it up, and put it back together if I found no major damage, which has been the case so far.

Just curious, but why do the parts need to be machined if they are not worn or damaged? The carbon build-up and rust came off with just gasoline, a wire brush, and a bit of wet/dry here and there.

Should I just bring it to a repair shop and let them rebuild it from here? Have I at least saved myself some money by handling the tear-down? Or are you saying to just let a machine shop reassemble the block, then I put the motor back together? How do I know if they use new bearings and not re-use my old ones (which seem to be in great condition)? Do machine shops offer warranty?

Sorry for all the follow up questions, but thanks for the advice?

 

[smokeonthewater]

You can likely reassemble it by yourself but you will need a service manual and you need to do a bit of reading on basic engine knowledge mainly because you need to know the correct terminology to read the manual.... The parts may not NEED surfaced but they need to at least be checked by someone who absolutely knows what they are looking at.... It would not be a terrible idea to have a pro put the engine back together but that doesn't mean you CAN'T do it.... Since I've never met you I really have no idea of your mechanical aptitude.

What some folks can do half asleep with a hangover can give others fits on their best day and it is not just a matter of education or lack thereof....

 

[THEFERMANATOR]

You do NOT turn the crank in a 2 stroke engine, and you do NOT use regular wet dry sand paper on them either(only use 1000 grit or higher crocus cloth). The crank and rod surfaces are machined to a mirror finish and then hardened. In a 2 stroke the bearings do not ride on a cushion of oil, so the surfaces MUST be a much harder finish, and must have a mirror finish as well. The actual bearings are made of a soft material, but the crank and rods are have a HARD surface on them. In a 2 stroke when the surface is under factory spec, you either have th crank rebuilt(welded, turned back down to stock, and heat treated. VERY EXPENSIVE to have done right), or you replace it with either a good used one or new one. Also rememebr that since in a 2 stroke there is no cushion of oil present, the bearing tolerances must be MUCH more precise.