RPM cutout at cruise

[piers]

I have twin 1997 johnson 150 oceanrunners.All has been well for 5 years since I have owned the boat.The starboard engine now when at cruise, aprox. 3800-4000 rpm,and after running normally for 15 min. will very abruptly drop about 500-700 rpm and then bounce right back up to cruise rpm.It will stay there for a bit and then drop abruptly again and then it will start biuncing around eratically.I bring the engine down to idle.I idels normally, give it a min. or so bring it back up to criuse rpm ,it runs well for a short while then it starts all over again.Any ideas???thanks in advance.......j150exeuc

 

[tashasdaddy]

Re: RPM cutout at cruise

sounds like you have a coil or power pack heating up and failing. you need to immediately check the spark, at that time. the unit cools, and starts working again, then fails again.

 

[piers]

Re: RPM cutout at cruise

Thanks for the reply.I am looking in my service book and it show that there are 3 types of coils installed on this engine.Charge Coil, Power Coil and Ignition Coil.Which of these coils could be the likely suspect also keeping in mind that it could be the power pack...

 

[skipper6567]

Re: RPM cutout at cruise

Hi I would start by putting the coils/power pack on the engine that runs good and see if the problem persists, do one Item at a time,coil then power pack. That way you will be able to determine whether it's the pack or a specific coil. hope that is helpful. they are famous for heating up/expanding internally and losing a contact,also make sre ther is no corosion on the boot or lead wires,look close it may be way inside a rubber boot connector.