Piston and Head Pics!!!! What Happened

[Bobbuff]

I am trying to treat the problem as well as rebuild what happened. Can someone please give me an idea as to what would cause.

 

[nickj718]

What does the spark plug look like?

 

[Bobbuff]

When I got it dry and brown.... This happened four years ago I just bought the boat and I am replacing everything but don't want it to happen again obviously.

 

[FinnExplorer]

Could be many things... lean condition, bearing that gave up with age or water/rust in it...

this is what my engine looked like last summer when connecting rod bearing gave up in the ripe age of 16

 

[Bobbuff]

How much did that cost ya to fix?? Did you have to take it somewhere or did you do it. I have never done a rod bearing

 

[FinnExplorer]

Since I live here out of reach of cheap SBT engines, I did it the harder way Hit the ebay for new assembled crank... first thought of only buying the bearings and seals but wasn't sure who could press the crank back together. Pulled the jugs and took them to machine shop for overbore once again(long story ) got the verdict and bought new oversize pistons, top end bearings and complete gasket set. Shipping and all the work and parts all together, well I haven't checked around 1000€ at least. Most of the work was done by myself except boring the cylinders. But now I have engine that will last long and I know exactly what was done to it.

The color of your plugs seems to indicate that you weren't running lean at least. Too bad with the fuel here, plugs haven't been brown in ages

 

[Guest_User]

what color are they supposed to be ff not brown. the darker the color on the plug nose usually means rich... the lighter ash or white color indicates lean. a black piston crown with no piston wash indicates lean, so you have to look at each part individually...

and then "oil" rich is another...

 

[Bobbuff]

So what you are saying Pale Rider if I understood you correctly is it looks like mine was running lean. Would that have been the cause for the break down of my piston? I have no damage to the cylinder walls only to the top of the piston and the head. Also is there any way to repair the head without replacing? Also I did the best I could at inspecting the lower half and heard no strange noises or seen any water in the oil. I am thinking I should be ok with just a top end rebuild. What do you think.

 

[Waterluvr]

Bobbuff, are the rave valves still in one piece or does one look like one's been replaced after the fact? If one came apart that could have sent metal grenading into that motor. ~Clean and inspect those just to be sure. It could have been something as simple as a piston pin clip that let loose, did you find both of them securely retaining each piston pin when you pulled it down, how about the rings all there still?

There's metal missing somewhere that caused that, you just have to find it that looks just a little to bad to blame on a nasty chunk of carbon letting go and chewing up the insides of you motor.

Also, take a caliper and measure the width of the pistons and interior of the cylinders just to see if that motor's had some top end work done before.

 

[Bobbuff]

I was thinking there is metal somewhere as well.. I did find all the clamps though and the rings where in place just sheared and melted to the piston....but there was no damage to the cylinder walls which makes me think it was just carbon...I know it surprised me too but no damage at all to the cylinder walls...running my finger over it and its as smooth as a new..I have the 717 which doesn't have the RAVE valves by the way...the new kit is supposed to be shipped out today so we shall see as for now I am working on the suggestions you made in the other post as well