#4 piston chewed up on top.

[rhtbird]

I'm working on my 1974 135 Evinrude. I'm replacing my 135 heads with 115 heads, because of broken bolts in the head cover. Cylinder 3 had a small amount of oil with water, less than a thimble full. I think because the head bolts were loose. Piston #4 was chewed up at the top as well as on the head. The gasket was not perfect. It had a couple of small holes at the top o cylinder 4 and the bottom of cylinder 2. With the exception of 4 the cylinder walls are pretty good. 4 has a small scratch that I think would be fine if I sanded it down. <br /><br />Can anyone offer advice?<br /><br />Thanks,<br /><br />Greg Hodges

 

[rickdb1boat]

Re: #4 piston chewed up on top.

You may be able to have it honed out if it isn't to bad. Are you going to replace that chewed up piston?

 

[rhtbird]

Re: #4 piston chewed up on top.

Can I get away without it? I'd like to get the boat in the water this year. <br /><br />Greg Hodges

 

[Chinewalker]

Re: #4 piston chewed up on top.

Hi Greg,<br /> More than likely you have a broken piston or piston ring. It ain't gonna get any better. At present, in all likelyhood, you have a lightly scored cylinder wall that could be taken care of with a hone. Install a good used piston (standard bore pistons are a dime a dozen - most marinas replace all four if one goes bad), some new rings and a seal kit and you'll be on the water on the cheap, with a more or less rebuilt motor - more of an indepth tune-up. Let it go and you'll be in for a major rebuild. If you've got the time and a good manual (Seloc #SE-68), you can probably do it inside of a week working a couple hours an evening.<br /><br /> Even if you're going to have the whole engine overhauled at some point, I would do it now rather than later. Why risk taking out the crankshaft or some of the con-rods, or putting a hole in the block?<br /><br />- Scott

 

[rickdb1boat]

Re: #4 piston chewed up on top.

I would'nt want to risk tearing up another head if I were you. I don't know how bad the Piston is, so I really can't say for sure. Can you post a picture of the Piston and Cylinder in question? If the piston is torn up bad, there is a good chance it will get worse real quick! It may also tear up you block to the point where you will have a Major expense, whereas right now it is repairable faily cheaply. Again, Pics would be very helpful!

 

[rhtbird]

Re: #4 piston chewed up on top.

Checked compression. 1,2,3 @ 135. #4 - 0. I'm guessing the rings must be gone. I guess I'll have to tear it down. <br /><br />Greg Hodges

 

[Dave H]

Re: #4 piston chewed up on top.

Currently have a similar expierence with my Force 125. Pulled the head and discovered the #1 and #3 pistons "chewed up" on their tops. #1 being particularly sever. Considering the damage, the cylinder walls looked in fair shape. I could only see minor scratchs. I thought that if I threw a ring that the physical evidence would present itself as sever scaring of the cylinder walls. However others tell me that it could have also been a piece of the Reed Valve within the Carb intake manifold. So I removed the carbs this week and did not notise anything "missing". So at this point I'v decided to go ahead and do a major rebuild. <br />One thing I did learn and will pass on is that before you re-install the head. Place it on a sheet of glass and with a feeler gage, check clearance. On my motor I was advised to have no more than a .004 margine. If greater put some med grit sandpaper on the glass and "wet" sand the head in a figure 8 pattern until clearences are satisfied. After reading alot of post conserning "blow" head gaskets. I wonder if most of us shade tree mechanics are aware of this step.

 

[fivestar]

Re: #4 piston chewed up on top.

Thanks for the advice. I've never heard that.<br /><br />Greg Hodges<br /><br />P.S. Goodluck with your rebuild.