Mercruiser Problems

[shavdog]

I just bought boat with a 5.0 mercruiser. its a 1998. The boat has an issue:<br /><br />Number four cylinder is dead...The seller claims the boat ran fine....Maybe, according to him it did. Anyway, I took it in for winterization and they are telling me they started it up, there was a miss and did a compression test and leak down test and determined the number 4 cylinder dead...Anyone with some past experience have a clue what might be wrong?...like a valve issue, head gasket issue, etc....they cant work on it until november as they are knee deep in winterization.. I just wanna be prepared when they start and be able to ask the right questions. If the boat runs fine....according to the seller, is this issue likely limited to the one cylinder? thanks for your help..5.0/305 mercruiser....1998 model...thanks<br /><br />Second question: On a bent prop shaft...is it immenent that th lower unit would have to be replaed? No one has said that but I want to be ready. They did tell me that the shaft alone is 400....this sound reasonable?<br /><br />Please don't ask why I bought this boat....Trying to analyze that myself....thanks for any help...craig

 

[Don S]

Re: Mercruiser Problems

Like I said on the other forum and email, they can use the leakdown test to determined if it's a valve or piston/ring problem. But untill the head is pulled you won't know why for sure or if it's a compound problem where a valve broke and went through a piston.<br />Without pulling the head, you will NEVER know for sure.

 

[shavdog]

Re: Mercruiser Problems

Thanks for your response don...I went other to the other forum and did not see any response from you nor did i receive any email...but thanks for your comments....it helps. craig

 

[Don S]

Re: Mercruiser Problems

Check your ezinbox mail, I replied to the email you sent there in more detail.

 

[Bt Doctur]

Re: Mercruiser Problems

Most likely is that the riser had a small leak and "Tuliped" the valve or caused it to stick in the guide. The miss condition is a tip off.On centerrise manifolds the cylinders 3,5,4,6 are most prone to have this type of problem. The head needs to come off to be sure its not a dropped valve or damaged piston.

 

[deputydawg]

Re: Mercruiser Problems

I used to work in a shop that had a fiber optic camera. This was a camera with a flexible tube about 3 feet long. It was used to insert into spark plug holes, dipstick tubes etc. and look at the interior of your engine. My current job we use similar equipment for vehicles for smuggling of stuff. They cost around $200 to $250. If you can find a shop that has one of these, it may make your decision easier.<br />If not, you will need to pull the head off and see what they mean by "dead cylinder". Could be one of about 6 things, or a combination of.<br />good luck and let us know.