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Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3341
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I have twin 2 stroke 150 mercs. I just got dockside fuel.

Customer Question

Hi. I have twin 2 stroke 150 mercs. I just got dockside fuel. Shortly after hit a large wake. One motor lost rpm an stalled other just had reduced rpm. Got motor started, but it developed a knock. It occurs at idle and at power. It also occurs if I disengage gear and just give throttle. Any ideas.
Submitted: 4 months ago.
Category: Boat
Expert:  Charles replied 4 months ago.

Hello, my name is***** will assist you.

Do you have the serial number from the engine?

Customer: replied 4 months ago.
It's a 2002 150XL SWB serial # *****
Expert:  Charles replied 4 months ago.

Thanks, ***** ***** that you are going to need to do is a compression test on the engines. Lets make sure that the blocks are in good shape.

Customer: replied 4 months ago.
Ok. Won't be able to do that til tomorrow. Can I follow up then?
Expert:  Charles replied 4 months ago.

Sure can. There are no time limits here. Simply reply when you are ready. If I am on, I will relay then, if not, I will when I return.

Customer: replied 4 months ago.
I'm back. Did a compression test. Looking at the motor from behind, the bottom left cylinder had 30 psi less compression than the others.
Expert:  Charles replied 4 months ago.

That would be #6, what was the reading on it?

Customer: replied 4 months ago.
65 psi
Customer: replied 4 months ago.
Motor runs normal except for the ticking.
Expert:  Charles replied 4 months ago.

That is not good. 90 is the minimum on this engine. You are going to need to pull the head and check out the cylinder to see if it is scored or not.

Was there any aluminum on the spark plug?

Customer: replied 4 months ago.
Ok. There wasn't any aluminum on the plug.
Expert:  Charles replied 4 months ago.

That is a good sign. Maybe just a failed o-ring on the head.

Customer: replied 4 months ago.
I'm going on a week long boating trip. Mostly anchored. Have two outboards if this one stops. What can I expect to happen if I continue use.
Expert:  Charles replied 4 months ago.

With the ticking sound unsolved, it could lock up.

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