Sounds like it is missing at idle. 4 cylinders are much more noticable when
they have a miss since each cylinder is 25%. Problems with the idle fuel
circuit in the carb maybe. Raise the idle speed a little bit and then
remove one plug wire at a time while it is running and see if it changes.
If you find that removing one of the plug wires has no effect on the idle
then that is your problem cylinder and it may be ignition related. If every
plug wire changes it when removed then you have a random miss and it is more
likely fuel related.

wrote in message
oups.com...
I have a new 2007 Bayliner 185, with a Merc 3.0L 4Cyl engine, and an
Alpha 1 outdrive.

My issue (my dealer's issue to be more accurate) is this:

At idle, warm or cold, the engine vibrates horrendously, to the point
where it resonates (shudders) throughout the entire boat, shaking the
gunwales. The idle is currently at about 600 RPM. I have also
noticed that when I took the boat out of the water, the transom has
some black film on it. At speed, basically anything above 1100 RPM,
the engine performs perfectly. The boat has about 3 hours on it at
this point. It is going back to the dealer tomorrow for this issue,
but I was wondering if anyone else had run into a similar problem?

Other than this, I have been pretty happy with the boat. It planes up
in seconds, delivers the promised 42 MPH (on GPS) and is very stable,
even on the choppy early spring waters of Lake Erie.

Thanks,

Randy.

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