40 mlht

[Prairieboater]

I've got a 40 2 stroke with running problems that I can't iron out. The model number is 40 MLHT 6H4 L 490464 Y. I've cleaned the carbs, replaced the spark plugs, compression is 110 on all 3 cylinders, ignition coils and plug wires test within specs. This motor starts well and will idle smoothly all day long. When I accelerate from an idle, it will drop one cylinder but as the engine picks up speed it will begin to cut in and out on the dropped cylinder and then it will cut in on all 3 cylinders and run just fine. I can then stop the boat and will repeat this when I accelerate it again. I'm feeling stumped on this. Any ideas?
Thanks

[panasonic]

You will need to post the exact model number that is on the transom bracket data plate to get proper help.

[99yam40]

I would check the fuel pump to make sure it is not leaking extra fuel into #3 crankcase.
too much fuel in a cylinder will also not let a cylinder properly

what do the plugs look like?

[Prairieboater]

You will need to post the exact model number that is on the transom bracket data plate to get proper help.

Thanks Panasonic. I edited the original post with those numbers.

[Prairieboater]

I would check the fuel pump to make sure it is not leaking extra fuel into #3 crankcase.
too much fuel in a cylinder will also not let a cylinder properly

what do the plugs look like?

The plugs all look good. I don't see anything out of the ordinary. I never thought of a fuel pump that might be leaking into the bottom of the crankcase. It does act as though it's trying to clean out a gas fouled cylinder when accelerating. That accumulation of fuel likely wouldn't purge out of there at an idle.

[99yam40]

that is my thought also

but then not enough fuel will do it also.
could be pilot jet/or passages not letting enough in at low RPM

measuring peak voltages might make sure each coil is getting the voltage needed if pump is not the problem.
and make sure the fuel is not bad or has water

[Prairieboater]

I'm going to check into the fuel pump first. I'm confident that the fuel is good with no water and the carbs are clean and flowing fuel properly. If the fuel pump idea doesn't pan out, I'll look at peak voltages. It's going to be a few days before I can get back at it again but I'll post my findings after I get a look at it. Thanks.