Hi all. I have a merc 200 efi yr 2002
it goes well. 40!knots top speed on my 5.9m voyager.
it doesn’t idle great and can smoke a bit a times
so I got a compression test done. They were all between 110 and 120!psi bar one which was 90.
my question is . Is it worth fixing and is it safe to continue to use.
im not mechanically minded. So your thoughts would be a great help.
cheers.
I would wet test the cylinder in question. Spray in fogging oil thru the plug hole and comp test again. Is the reading now higher? Does the engine idle better once it is fully warmed up-say 6-8 mins ? Both can tell you if it's worn or stuck rings. 1st you can attach a remote fuel tank to the motor with 2-3 gallons fuel with a strong mix of quik kleen, carbon gard etc. (a whole 12 oz bottle. Let it idle at 1K for an hour. Best ever would be Yamaha motor tune. Only a dealer can buy that stuff. It can cure sticky rings. If you happen to have any luck with the above you should follow up with a full decarbonization of the motor. This involves pulling the rear exhaust plate and divider and both cylinder heads and manually clean the exhaust ports, piston domes and cylinder heads completely. If you pull the exh plate you can 'spring test' the piston rings with a screwdriver tip telling you if they are stuck. Or if you pull the cylinder head you can check the low one for deep grooves, scoring or out of round wear. You can even buy an inspection camera that apps and plugs into your cell pn to see in thru the plug hole! So, decarbonizing can save the engine assuming you commit to using quality oil (partial or full synthetic), keep quik kleen additive in every tank of fuel. I'd also be sure to run mid grade fuel 89-91 oct. Ethanol free if possible.
Many thanks for your lengthy reply. I appreciate your time and I will look into it.
why only use 91 or 95 fuel. I have been using ethanol
Thanks again
Mercury Marine has always recommended mid-grade octane fuel 89-91 or higher. It's hard to find 91 anymore. At least in the Chattanooga area. Minimum rec'd octane is 87. And non-ethanol whenever available or affordable.Originally Posted by Tower5
I’m in Western Australia and 91 is the lowest petrol.how much fogging spray should I put in there. Is it worth leaving over nite. I was going to do all cylinders. Would you agree
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