Mercruiser shaking in idle

M

mamadog

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May 20, 2012
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I am a new boater, I have a 1998 18' sea ray with a mercruiser 3.0 alpha 1 I/O, it recently started shaking pretty bad in idle. I have been running it for about 3 months now, did an oil change and changed the alt belt and spark plugs,the boat was running fine until about a week ago when the shaking started, there is no problem at high rpm when running,only at idle. Is it possible the alignment is off or the motor mounts are loose? I'm a newbie looking for answers, thank you
 
Don S

Don S

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62,321
Re: Mercruiser shaking in idle

Alignment/mounts are not your problem. You should be looking into tuneup, reading spark plugs, doing compression test, looking at the carb for lean fuel at idle, etc.
 
M

mamadog

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Re: Mercruiser shaking in idle

How do I do a compression test and check for lean fuel?
 
S

stonyloam

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Re: Mercruiser shaking in idle

mamadog said:
How do I do a compression test and check for lean fuel?
Click to expand...

Go to Autozone and borrow the tools, and follow the instructions, pretty easy to do. In the meantime, while at idle pull the plug wires one at a time to see if one cylinder is not firing (when you pull the wire on the bad cylinder it will have no effect).
 
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