running rough over 2500 rpm's

[175 backtroller]

I have a 1993 60 hp vro that is running rough over 2500 rpms. I have recently rebuilt the carbs, changed out the coils, checked the compression, changed the fuel filter, the timer base moves smoothly. So those should not be the problem. The engine was running great after all this was done. Out yesterday and it started running very rough over 2500 rpms, the engine was shaking quite hard. I am thinking it may be the power pack. Any thoughts?

 

[Okee Jimmy]

Re: running rough over 2500 rpm's

I think your motor is going into slow (speed limiting operational warning). This is built into your ignition to prevent engine damage due to an overheat, or no oil condition, limiting your RPM's, and sounding like a severe misfire. If you are sure you have oil flow into the motor, and the motor is not overheating, you can temporarily disconnect the temp sender wire at the cylinder head, (tan) and disconnect the electrical connector from the VRO pump. If the problem goes away, one or the other is bad and will have to be replaced. If not, look for grounded or shorted wires in the harness.

 

[CharlieB]

Re: running rough over 2500 rpm's

It will get very expensive throwing electrical parts at a motor when you haven't diagnosed a problem.

CDI published an excellent Ignition Troubleshooting Guide, it is here on iboats and the CDI websites. Use it to help diagnose and PROVE a component bad BEFORE replacing it.

Your ignition is very susceptible to RF interference, often the wrong spark plugs OR a temp sensor wire too close to a spark plug wire can cause a problem such as you describe.

 

[clanton]

Re: running rough over 2500 rpm's

The only sensor that sets S.L.O.W. is the overheat sensor. Check the power pack grounds.

 

[Raymorgan]

Re: running rough over 2500 rpm's

I have a similar problem with a 115. does yours runs ok for a short while then start acting up, or does it always do it?

 

[175 backtroller]

Re: running rough over 2500 rpm's

It had been running great until this happened. I was on my way in from a 10 mile or so run and it started acting up. I am going to try the tan wire and also check the thermostat. No signs of overheating. I will make a test run on friday so i will post the outcome.

 

[175 backtroller]

Re: running rough over 2500 rpm's

Unplugged tan wire and problem solved. Replaced temp sensor and runs like new. Thanks for the help.