Low RPM, Vibration

[jamepc]

I have a 2001 Islandia, 240 Merc EFI. The RPM's won't go above 4900-5000 RPM's. I did a compression check and all were around 130 psi. Next, I would like to verify all cylinders are firing. What's the easiest way to do this? If 1 or more aren't running, how do I tell which ones? Any other ideas or suggestions regarding this problem are appreciated.
Also at idle to about 1500 RPM's the engine is extremely rough. Very shaky like a cam with a lot of overlap in a car. So if all the cylinders are firing, maybe something else is off balance like a bad impeller? Would this also slow the engine and boat down?
Thanks,
James

[centerhill condor]

well, since you mentioned the impeller...how 'bout checking to see if there is debris in the pump.
Also, if it is bad at idle you could pull one plug wire off of the distributor at a time and see if it gets better or worse. If it stays the same there is the problem cylinder.
Saturday night freebie! good luck.
CC

[Sleeper CP]

To see if all cylinders are firing take the plastic end of a screwdiver while it is running and touch the exhaust on each cylinder until the plastic starts to melt. Easy way to see if all are firing. Also, check the driveline to see if it is tight.
Sleeper CP

[Sleeper CP]

What did it used to rev before this occurred?
Sleeper CP

[Skip3]

To see if all cylinders are firing take the plastic end of a screwdiver while it is running and touch the exhaust on each cylinder until the plastic starts to melt. Easy way to see if all are firing.
that's no way to treat your tools!!!!!!!!!!
I use a spray bottle with water in it ..

[Sleeper CP]

that's no way to treat your tools!!!!!!!!!!
I use a spray bottle with water in it ..
I'll qualify that :"take a cheap screwdriver" not Snap-on or Proto.
Sleeper CP

[jamepc]

The operating RPM's on this should be 5700-6000 RPM's. Top speed was 45-50 MPH. Now it's at 4900 RPM's and 30 MPH. With 3 or more people it won't even plane.

[Sleeper CP]

Have you replaced the fuel filter?
Some years ago our jet laid down couldn't figure out what went wrong for 3 trips to the water. Finally read something somewhere, pulled all of the MSD plug wires took them to a friend to test. 3 of the 8 went bad, maybe to close to the headers or something. The engine was basically running on 5 cylinders, but you wouldn't have known it from looking at the plugs. Replaced all the wire and Bingo, ran like a champ again.
Sleeper CP

[jamepc]

I'll check that stuff, thanks.
Also, how should spark plugs look in this 2 stroke. They always have a black film of oil on them but that normal, correct?

[rerfert]

2 stroke gas/oil mix
Too much oil (OR cheap oil) in the fuel will foul out a plug quick....If the plugs have any age on them start with a new set.
I also use an infra-red thermo-meter to find non firing cylinders.:idea: