Mercruiser 5.0 RPM gauge fluctuates

[JH3]

MY RPM GAUGE FLUCTATES. I PULLED THE PROP AND THE COLLER IS NOT CRACKED OR STRIPPED. THE ENGINE DOES NOT SURGE. I DID FIND A LOOSE BOLT ON THE MANIFOLD AND TIGHTENED IT. THIS SEEMED TO REDUCE THE FLUCTUATION BUT DID NOT ELIMINATE IT.<br /><br />ALSO MY VOLTAGE GAUGE IS FLUCTUATING. ANYONE HAVE ANY IDEAS ON THE CAUSE?

 

[Ralph 123]

Re: Mercruiser 5.0 RPM gauge fluctuates

Just a guess but it sound like a lose wire on the ignition side (I terminal) of the gauges or the grounds (G terminals). They are often wired in a daisy chain (one gauge to the other) and if you have a lose connection in the chain you could get jitter in the gauges as the connection is made and broken. Just a guess but worth checking

 

[marunr]

Re: Mercruiser 5.0 RPM gauge fluctuates

What is the make and model of your boat and motor? On an omc there are 2 50 amp fuses which can become corroded with age or moisture causing a bad connection which can affect the tach. Also check the connection on the - side of your coil...may be loose.

 

[JH3]

Re: Mercruiser 5.0 RPM gauge fluctuates

IT is a 1999 bayliner 2050 capri with a mercrusier 5.0 i/o. Is that enough info.?<br /><br />The tach surges kind of like a tach does in a car with a slipping clutch and then drops back some. I pulled the prop and there is no evidence of slippage or cracking on the coller (the plastic coller that fits over the shaft)I don't know what it's called.<br /><br />The motor is a year old.

 

[Flukinicehole]

Re: Mercruiser 5.0 RPM gauge fluctuates

I would guess you have a bad ground to your tach.

 

[M2]

Re: Mercruiser 5.0 RPM gauge fluctuates

I had the same problem and I removed the wires from the back of tach, pinched the connectors a little bit to make better connection. Put them back on and the tach worked just like it should.