Throttle issue?

[Auftiuk]

I have a 2006 Crownline 180BR with mercruiser 3.0 engine. Here is the issue…. When going forward at low speed, the tachometer goes wild, swinging wildly and rapidly from 2000-4000 RPMs even higher. I do not hear the engine revving or changing the RPM, but once in a while, it sounds like it may be shut off, and a few times it has shut off. The engine idles fine about ~ 630 RPMs… mid speed and high speed no issues.

Fuel/water separator filter is new, Fuel pump is new, carburetor is clean, spark plugs are new and working on testing, ignition coil is new and working.

what could this be? Is it a problem with the throttle cable and assembly? Any pointers will be much appreciated.

 

[alldodge]

Could be a the Tach is going bad. If it does it will kill the motor

Disconnect the Gray wire to it and connect a handheld Tach to see if it does the same thing

 

[Auftiuk]

Thanks… I will check it.

 

[Maverick7]

I had a similar issue. RPM gauge would almost “bob” up and down at random times. On the back there is a selector switch that corresponds to the number of cylinders your engine has. Sometimes the contacts under that switch get corroded. The remedy is to just flip the switch back and forth a few times to basically break up that corrosion. When your done flipping it back and forth, just make sure that you turn it to the “4” position. That’s assuming you have a 4 cylinder engine.

Might be your issue, might not. But either way, it’s a simple and easy (and free) place to start.

 

[Auftiuk]

Thank you, Mavrik7! I’ll try it.