Serious problem ~ Opinions and help needed

[Razzman]

I know this should be in the technical section, and it is but under another topic. I posted here to get maximum exposure to this problem. I've had a leak somewhere since we got the '95 2000slm comp, I found the leak all right, it's a cracked head. The leak only shows up when above idle and with a load on the engine. here's what i posted in technical;

I wish it was a freeze plug! I pulled the exhaust manifold and cleaned the side of the head real good and watched water seeping through the casting in two places between cylinders 2 & 4 along a line i suspected was a crack.

We took it out Sunday to find the leak and up until then it has run perfectly. Sunday however was different, it didn't want to start and when it did finally start it ran rough until i got going a bit. Then it quit after awhile like it was starving for fuel. If i let it sit it restarted but wouldn't take a load so i had to idle in to the marina. What bothers me is that when it did restart it blew pure white smoke out the exhaust which i suspect was steam from compressed water in a cylinder.

The funny thing is that it ran perfectly smooth at 10 mph without any hesitation at all. I'm going to pull the head Saturday and see what's up inside. From the outside looking through the exhaust ports the valves look good with no sign of water so who knows. Also you should never do just one head so I'll end up having to do both if the block is ok. Oh well such is life huh? My super deal may not be so super after all! The wife is bummed and stressed over this ... sigh

I'm debating on replacing th head, finding a low hours used engine, rebuilding mine or ? Any thoughts?

[chpthril]

If no water in the oil, my gut says the block is not cracked and should be ok. down side of running hot is that it tends to ob-long the cylinders and take the spring tension out of the rings.
here is how I would approach if mine!
1) do compression test on all cyl. to get a 'baseline'
2) do a cylinder leak down test on #'s 2 and 4, and any others that have low comp.
3) pull the cracked head off and inspect both head and block. any cylinder getting water in it, the piston looks as if it was steam cleaned. Inspect the cylinder walls by rotating the crankshaft so the piston is all the way down. A crack should be easy to see, but also look for the piston rubbing the cyl wall. The walls should be a smooth grayish uniform color, may still have the 'cross-hatching' from the original honing. IF it's blue, it's been hot with little lube between the rings and cylinders. If the walls are rough and scored, the piston has been rubbing, you will see this on opossing sides of the cyl if it's out of round.
4) From there, you will know whether you can go with a head or a longblock.



Hope this helps, Mike

hear is a link to some pics ofPiston scuffing

[Razzman]

I saw no indication of water in the crankcase or under the fill cap on the valve cover so I'm of the opinion it hasn't entered the cylinders or hasn't passed by the rings at least. I plan on pulling the head this weekend to see what's up. This leak has been present since i got, the local dealer could never find it.

I had a compression check done when i got the boat a few months ago and have only put 6 hours on it since. All the cylinders were in the 155-160 range with the exception of #8 which was around 148. Looking into #8 through the exhaust port the valve stem is almost white and way to lean. I guess I'll know when I pull it.

Thanks Mike, I'll keep ya posted as to what i find.

[chpthril]

good so far

rule of thumb: your lowest should be within 75% of the highest, 120psi would be your minimum.