RPM & Trim Gauge Question

M

modicon2

Seaman Apprentice
Joined
Apr 17, 2008
Messages
48
I've got a 1989 WellCraft with 3.7L Mercruiser and Alpha-1.

The RPM does not work. The gauge is displayed x100....it reads 20 with engine and key off. When I turn the key on it goes to 0. When I start it and running it still reads 0.
Are there somes check I can do to determine if it is the gauge or something else?

My boat does not have a trim gauge. What is required if I wanted to add a trim indicator gauge?

Thanks...
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,762
Re: RPM & Trim Gauge Question

Tachometer needles will "float" when the key is off -- meaning it is rather typical that it hangs somewhere on the lower end of the scale. If it goes to zero when you turn the key on, that says it is getting power. But the fact it does not register when the engine is running, says the signal or sense line is disconnected or a sense signal is not being received from the engine. That wire is on the "S" terminal on the tach and comes from the engine. Trim gauges are easy to install but you also need a trim sender that attaches tot he outdrive. You might check the drive as it may already have one. The sender and the gauge must match.
 
amynbill

amynbill

Petty Officer 1st Class
Joined
Sep 22, 2007
Messages
242
Re: RPM & Trim Gauge Question

Just learned this...on the back of many tachs is a little adjustment dial that you can turn with a small flat head screwdriver. It is for engine selection (v6, v8, etc...)

Mine was not working when I did my sea trial, and when we looked, it was set on the v6 model (standard). I opted for the v8, so the fix was a 5 second turn on the back to switch it to v8.

I also learned that if it is left "in between" it will react funny, and not respond sometimes. You could look to see if maybe yours is in between...maybe it slipped there?

Worth a shot before you go to the next step.
 
M

modicon2

Seaman Apprentice
Joined
Apr 17, 2008
Messages
48
Re: RPM & Trim Gauge Question

Thanks for the advice....
I'll be working on it this weekend.

Thanks again
 
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