New rings... Old engine??

[TBarCYa]

My 1981 115hp Evinrude is in need of new rings and one new sleeve. Is this procedure any more complex than putting new rings and sleeves in a 2-stroke dirtbike?? The reason I ask is because I was told today by a marina that I'm better off buying a rebuilt power head than putting new rings in this one. Three of the sleeves look to be in excellent condition and I can't imagine what they would need other than new rings. The only thing I can think of is that the guy I spoke with this morning was trying to sell a rebuilt powerhead.<br /><br />Thanks..

 

[Dhadley]

Re: New rings... Old engine??

What did they measure? Why do you say a sleeve is required?

 

[TBarCYa]

Re: New rings... Old engine??

Compression is 110/30/90/90 and the cylinder at 30psi has scores in the sleeve that can be both seen and felt. According to the Clymer manual, compression in all cylinders should be greater than 100psi. Fortunately, all pistons appear to be in useable condition. <br /><br />I'm not sure if the scoring of the one cylinder is beyond what honing the cylinder can correct but I think I will attempt it prior to ordering the sleeve. My plan is to remove the ridge at the top of the cylinders, hone the scored cylinder, and install new rings in all 4 cylinders. The other 3 cylinders all still show the crosshatch in the bores so I'm not going to bother honing them unless they're out of round.

 

[Dhadley]

Re: New rings... Old engine??

Oversize pistons for that motor run .020, .030, .044 and .064 so I'd bet that if its standard now it'll clean up without having to be resleeved. I'd also bet that if its standard the other cylinders are out of spec enough that they'll need to be bored. Once its apart and a marine machine shop (not an automotive machine shop) measures it you'll know what has to be done.<br /><br />Chances are that 4 pistons will fix you right up without sleeving. As long as the block is borable and the crank is good its most likely less expensive to rebuild that one. If time is a concern then a replacement is always quicker.<br /><br />If that 30 psi cylinder has broken rings its probably on the starboard side. If so make sure you change the set up to get the rpm up where the motor will live.

 

[TBarCYa]

Re: New rings... Old engine??

The pistons have STD stamped on them which I assume means they're the standard pistons. Ironically, I have never seen a motor of this age where the pistons were as clean and the bores as smooth and perfect (looking) as these. Except for the one which begs the question, why would only one cylinder not get enough fuel to lubricate the bore?? I'm assuming that it was a lack of lubrication that caused the scoring although as you mentioned, broken rings would easily cause the scoring but I would expect metal fragments or noise of some kind with broken rings. <br /><br />One other question (for now) I'm lacking in benchtop space so is it possible to remove the pistons with the powerhead still in the outboard??<br /><br />Thank you for your help.

 

[reeldutch]

Re: New rings... Old engine??

you have to remove the powerhead and split the crackcase to be able to take the pistons out and send the block to the machineshop.<br /><br />good luck