Engine one cylinder has compression other has zero

[PASTFAST03]

I just purchased a 1999 seadoo chaleneger one of the motors has perfect compression amd the other motor has compression 145-150 on the back (rearof boat) cylinder and the front has nothing. Any ideas

 

[bigJake]

my amateur guess is it was run lean and melted a piston.

 

[howie099]

use a flashlight to see if you see if the top piston is ok and if you can't see anything broken than squirt some oil in the cylinder and check compression again. For sure you will have take the engine apart but if the compression goes up the rings are just shot.

 

[NICK5590]

Ok thank you any type of oil?? An when I try to start it it started and shit off and when I tried again it turns over but back fired

 

[parrothd]

Ok thank you any type of oil?? An when I try to start it it started and shit off and when I tried again it turns over but back fired

No amount of oil is going to do you any good, 4 cycle engine maybe, you'll need to rebuild the top end...

 

[bigtexan99]

my amateur guess is it was run lean and melted a piston.

How does an engine run lean?

 

[bigJake]

if you still have gray fuel lines, they break down internally from the ethanol in the gas and plug up the internal carb filters thereby leaning out your fuel mixture. this causes the engine to run hot enough to melt a piston. so that's running lean due to decreased fuel in the mixture. another possibility is an air leak, eg the carb base gasket, in which case you have a lean mixture caused by increased air

 

[PASTFAST03]

ok took some stuff apart today i checked the pistons they move freely up and down, engine trys to start over but no go. i sprayed some oil in the cylinders and then did another compression test and nothing on the back one getting very low reading like a 20. all fuel lines are black.

 

[LouDoo]

I'm afraid the damage has been done, you've got a hole in the piston.

Lou

 

[howie099]

you might just need a new top end.

 

[NICK5590]

Ok finally got the top end out of the boat did not remove the whole engine the back piston was a all pitted and destroyed. so now I realize gonna be a little hard to remove the pistons. Any help would be greatly appreciated how do I go about removing the pistons the easiest way, thanks

 

[bigJake]

Ok finally got the top end out of the boat did not remove the whole engine the back piston was a all pitted ad drstroyed. so no I realize gonna be a little hard to remove the pistons. Any help would be greatly appreciated how do I go about removing the pistons eats the easiest way, thanks

I don't know the right answer but I am sure that eating the piston is NOT the easiest way to go sorry, couldnt resist....

 

[Seadoobuddy]

The easier way is probably to remove the engine to work on it.

Actually the easiest way is to pay some one to do it for you.

where in the USA are you? If in Florida, there are many members who could live near you and might be able to help.

 

[howie099]

It's harder to do the work in the boat than a Jetski. You have to hang in engine compartment and try to do the work or use a step stoll on the side. Pulling the eninge will be the easiest.

 

[NICK5590]

Sorry for a few spelling errors Iphone spell check... I live in longisland ny

 

[NICK5590]

hello are the pistons being held in by snap rings?

 

[El Toro 33809]

Yes they are.

 

[ocod]

Be carful of the 34 needle bearings when you remove the wrist pin form the piston.

I've read about placing magnets in a towel around connecting rod to catch any that fall.

 

[NICK5590]

ok thanks never heard of the pins having bearing but thanks for the heads up,

my cylinder head is a little pitted any suggestions.

also i am having fullbore.com any body use them?

 

[howie099]

I have used fullbore 3 times will good results. Thye did a yamaha GP1200, Polaris 750, and Yamaha blaster for me. The roller bearing is usually in the rod that the wrirst pin goes through. That is was ocod is talking about. And if the brearing is broken the little needle bearing will fall out everywhere.