Erratic Rev Counter first thing in morning - ideas??

[AndyP]

Hi guys,

I commute by RIB across Portsmouth Harbour daily and for the last few weeks my rev counter has been somewhat erratic first thing.

The reading flicks, with no change in engine rpm, down to 2,000 up to 4,600 and back again.

After a few minutes running under load it settles at the correct reading.

What is wrong?

Is it moisture inside the coils burning off as the engine head heats up?
Is it an intermittent wiring loom fault that just goes by itself after 5 minutes?
Is it a failing coil which temporarily works after a bit of internal heating?

Any thoughts?

The engine is a 40hp 3-cyl 2-stroke Yamaha on a 4m Searider and at 2,900 rpm the boat sits at 10kts going across the harbour.

Andy

[biffer]

my guess would be loose contection, check them and cable tie them up so they dont move around

[IBWET]

Originally Posted by AndyP

Hi guys,

I commute by RIB across Portsmouth Harbour daily and for the last few weeks my rev counter has been somewhat erratic first thing.

The reading flicks, with no change in engine rpm, down to 2,000 up to 4,600 and back again.

After a few minutes running under load it settles at the correct reading.

What is wrong?

Is it moisture inside the coils burning off as the engine head heats up?
Is it an intermittent wiring loom fault that just goes by itself after 5 minutes?
Is it a failing coil which temporarily works after a bit of internal heating?

Any thoughts?

The engine is a 40hp 3-cyl 2-stroke Yamaha on a 4m Searider and at 2,900 rpm the boat sits at 10kts going across the harbour.

Andy

Find where the installer of the rev counter made connections on it's way back to the engine - if all okay (fairly sure they won't be,next on my list would be the rectifier...then back to fly wheel mags etc..