700 Cylinder Head Cracked - Help!

[rrdo]

Last day on the lake. Submerged engine, got out all the water (I think), and then fired it back up out of the water. Ran good, but I believe I got it too hot and cracked one of the cylinder heads. Besides having to replace the cylinder head, any other suggestions as to what I must do? Any further damage besides the cracked cylinder head because of the water? Thanks for any suggestions and similar experiences. One more question - Will a topend job on the cracked cylinder be enough. Any cost ideas?

[Technical Support]

If you just cracked a head (would be the first time I saw that happen like that) you don't need a top-end job, just another head. I suspect you have some other damage, however, and need to tear it down.

How long did you run it out of the water?

[rrdo]

Hi Tech Support,

I ran it out of the water for about 30 seconds. Revved up good and sounded normal. I then placed it back into the water and tried to re-start. Would only partially want to start. Pulled back out of the water and checked engine compartment and noticed the crack in one of the cylinder heads. Assuming the crack occured between when I had it running out of the water and when I tried to restart in the water, because in the water, it never started.

[Technical Support]

You cooked it, that was WAY too long especially on an already warm motor.

[Technical Support]

If he's having running problems and cooked it enough to see a cover crack, the head is gone too.

[jedw79]

That would be a cylinder head cover and not an actual cylinder head that you see cracked if it is indeed a domestic engine. That is not to say that you don't have serious damage.

[jedw79]

Yes indeed I'm sure your correct. However, what if the crack was directly across from the flame arrestor (more critical if it's an aftermarket arrestor as I'm sure your aware) and would squirt water into the carb. once it was in the water and under pressure? I realize this is very unlikely but certainly not impossible. I basically just wanted to clarify that what he/she sees is not actually the cylinder head, but only a cover for the water jackets. Good day

[ September 04, 2003, 02:58 PM: Message edited by: jedw79 ]

[rrdo]

Hey Guys,

First thaks for all the responses and comments. To address some, the engine was stone cold when it got submerged (it was tied to the back of a houseboat and was overcome by the prop wash while trying to back off the beach). We immediately bilged the engine compartment and then hoisted the PWC onto the top deck of the houseboat. This is where we pulled the plugs and got the water out of the cylinders (700cc-two cylinders). Then replaced the plugs and fired it back up. Still believe I must of ran it too long. Like I stated earlier, it fired up and revved good. Hoisted the PWC back into the water and at first try, could not get the engine to start on both cylinders. Hoisted back out of the water and onto the top deck again. Was checking electronic box when we noticed that the forward cylinder had a crack on the side facing away from the carbs. It is down close to the base, but not at the base, and runs back towards the rear (second) cylinder in a horizontal manner. The actual heads (top of cylinders) are ok. The crack is definitely on the side of the cylinder. Hope this helps.

[Technical Support]

Ah - the CYLINDER is cracked...very different than the head or cover. I'm not sure what you[ve got goin on, but you need to tear it down - overheating doesn't cause the cylinder to crack.

[rrdo]

How about this thought - Did not have all the water out of the cylinder and the compression stressed the cylinder when it tried to fire off. As you know, liquid (water) cannot be compressed and maybe there was enough in the cylinder on the actual compression stroke to push the cylinder upward in a way that really stressed the cylinder wall. Maybe this is why the crack is horizontal and down close to the base of the cylinder. I guess anything is possible.

[Technical Support]

The outside of the cylinder is just water jacketing, the iron sleeve is what takes the force inside. It would take the rod snapping, blowing through the cylinders and often case, to crack the outside of the cylinder. I'm not sure what to tell you without more information and preferably, pictures.