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Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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Indmar 350. 2008 Moomba with 150 hours......Running rough

Customer Question

indmar 350. 2008 Moomba with 150 hours......Running rough and water in #6 cylinder when we take spark plug out. What is my next course of action
JA: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.
Customer: No water in the oil
JA: Is there anything else important you think the Marine Mechanic should know?
Customer: Some paint peeling on cylinder 6 side of engine. Might have gotten hot but no overheat wrning.
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Submitted: 4 months ago.
Category: Boat
Expert:  Tan replied 4 months ago.

Hello. My name is Tan.

I would start with a compression test. Blow all the water out of that cylinder before you do the compression test. If compression checks good start the engine. Let run for a few minutes at about 1200 rpms. Now shut engine off do you have water in any of the cylinders?

Diod you over heat the engine?

Is this boat used in salt water?

How many hours are on the engine?

Customer: replied 4 months ago.
No saltwater. 150 hours on engine. Engine has never overheated. Thinking failing exhaust manifold.
Expert:  Tan replied 4 months ago.

Yes manifold or riser. But with low hours it's hard to say and especially freshwater.

A sticking valve will allow the cylinder to suck water into the engine. This is the purpose of the compression test.

Did you have a following sea when in rough water?

Customer: replied 4 months ago.
Will try the compression test.
Expert:  Tan replied 4 months ago.

Ok if compression checks good put plugs back in and run engine for about 5 minutes at 1200 rpms. Then check for water in the cylinders. If you have water then we need to remove the manifold and riser and inspect. If no water it is possible it came in through the exhaust when you were in rough water.

Customer: replied 4 months ago.
It ran really badly last season..... Was losing power towards end of season on and off.... We decided to address it at spring tune up and this is what we found.
Expert:  Tan replied 4 months ago.

Ok the compression test is going to tell us what happening. If you have a stuck exhaust valve it will suck water into the cylinder. The piston going down creates a vacuum.

Was the spark plug rusty?

Customer: replied 4 months ago.
Spark plugs actually looked ok last season when we replaced them.
Customer: replied 4 months ago.
That was when it was running poorly.
Expert:  Tan replied 4 months ago.

Ok at this point we need to do a compression test and go from there.

Customer: replied 4 months ago.
Ok... Will do
Expert:  Tan replied 4 months ago.

Keep me posted... Thank you...Tan

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