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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3721
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I have a 2003 Optimax 200. Ran it Saturday. It ran good

Customer Question

I have a 2003 Optimax 200. Ran it Saturday. It ran good until I towed a guy in. After towing I ran down river, no problems until I stopped. I idled around a little and then tried to take off WOT. The engine rev'd up and then stalled. I got out of the throttle and at this point it seem to idle fine. I tried to take off again and experience the same thing. Then it started idling erratically and shut off. Then would not start. Luckily I was not far from the ramp and got back with trolling motor. The engine started for me to load, but then died again. Once home the next day I checked the compression. Not warm though... I am not sure what the PSI should be, but it is consideribly lower than other V6 engines I have had. Port upper:85psi, middle: 90psi, lower: 85psi, Starboard upper: 92psi, middle: 95psi, Lower: 87psi. Is this within spec? If so, what could the problem be? It seems to fuel related....
Submitted: 1 year ago.
Category: Boat
Expert:  Charles replied 1 year ago.

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

The compression is too low for it to run correctly. The bare minimum is 90 PSI on all 6. This could just be a carbon issue due to the towing. You can try and get a can of Mercury PowerTune from your local dealer. Remove all 6 plugs. Tilt the engine us some and shoot the PowerTune into all 6 cylinders. Allow it to sit over night. The next day, trim the engine down, have a towel or rags under it as the stuff will run out of the exhaust. Turn the engine over with a 15/16" socket to force the PowrTune out of the cylinders. After that, do another compression test. If all 6 are now above 90 PSI, go out and run the engine hard to get rid of the rest of the carbon. You may also want to replace the plugs.

Customer: replied 1 year ago.
What should the compression be? Should I be concerned? Will your recommendation get it back into spec or am I possibly looking at powerhead rebuild? Should I also replace fuel filters? If so, which? All?
Expert:  Charles replied 1 year ago.

Hello again,

The compression on a new engine is close to 120. On a used one, I look for at least 90 PSI on each cylinder. Doing the process that I explained MAY get the engine back onto specs. That really depends on how the cylinder walls themselves are. If they are scored from either a lack of oil or from getting hot, you would be looking at either a rebuild or a new powerhead. The PowerTune is always my first step in the shop to try and get a motor back to where I need the compression to be to make it run better.

For the fuel filter, send me the serial number and I will get you a diagram of it.

Customer: replied 1 year ago.
I'll try this weekend and let I know.
Can I continue to discuss with you? I don't mind paying for it but I do not want to be charged monthly. Is this possible ?
Expert:  Charles replied 1 year ago.

Yes you can get back to me. I am also sending you a phone offer if you wish to get me on the phone while you work on the engine.

Customer: replied 1 year ago.
I forgot to send you the serial number for the fuel filters:
You mentioned using Mercury Power Tune. Can you purchase this from Bass Pro? Can Seafoam be used with same results? or other brand?
Expert:  Charles replied 1 year ago.

Part 10 is the filter.

Sea Foam will not do the trick here. You should be able to get it at a Bass Pro.