Volvo Penta Tachometers not on the zero stops with engines stopped

[Momac]

I noticed on my friends boat (which has AD41 engines) both of the tachometers were stuck on about tick-over speed with the engines stopped . What causes this fault / how to fix it please ?

 

[mikegunn]

I noticed on my friends boat (which has AD41 engines) both of the tachometers were stuck on about tick-over speed with the engines stopped . What causes this fault / how to fix it please ?

 

[mikegunn]

The tachometer on my boat does that. If I want to see zero rpm after stopping the engine I have to turn the ignition switch back on for a second or so and the indicating needle returns to zero. It’s not really a problem because once the engine’s running the correct rpm is shown.
Mike

 

[Momac]

Yes I know its not really a problem.
But out of curiosity I would like to know what causes this to occur and whether normal operation easily be restored.

 

[Plum]

I thought that was nornal. Mine has always stayed at idle when switched off, then drops to zero when next turned on. There is no spring return, the needle is driven in either direction. With no power, key off, the needle does not move so does not return to zero.

 

[Momac]

The tachometers drop to the stop when I turn off the engine on my kad32 so I am thinking the tachometer sticking at the idle speed isn't normal. But I guess it could be normal on an AD41.

 

[madabouttheboat]

It is normal behaviour