RPM Gauge - works when you tap it!

[winbasic]

Hi,

I've got a Volvo Penta 5.7gi-b in an Aussie boat (Mustang) and after being stored over the Christmas break, the tacho doesn't work properly. If I tap it then the needle slowly rises but when I turn it off, it stays at the last known position. I can only guess what RPMs I'm doing based on the fuel flow meter and the sound of the engine.

My question is where do I start looking? Is it the gauge or if not, how does the engine 'talk' to the tacho? I know the speedo is via an air hose but I'm not sure if the tacho is by cable or some other mechanism and the boat isn't stored locally so I'm wanting a heads up on what tools to take when I have a look.

Thanks in advance!!

Kind Regards,

David.

 

[Don S]

Re: RPM Gauge - works when you tap it!

Replace the tach.

 

[winbasic]

Re: RPM Gauge - works when you tap it!

Hi Don,

Thanks for your reply - as a general rule, are they hard to replace? Is it just a case of a 'data' cable and then the screws that hold the unit to the dash or is there some kind of calibration I also need to do?

 

[Don S]

Re: RPM Gauge - works when you tap it!

Have no idea. Depends on the manufacturer of the boat and what they used.

 

[Rocky_Road]

Re: RPM Gauge - works when you tap it!

My Faria tach was doing the same thing--I would have to 'tap' the face and it would move to the correct reading.

I contacted Faria and they suggested that I try loosening the two mounting nuts...if they are over tightened it can 'hang' up the neddle. This worked for me, so you might want to try this first.

Then if you are still with an issue do as Don (the expert) says, and replace!

Happy boating!

 

[Black as]

Re: RPM Gauge - works when you tap it!

Hi,

I've got a Volvo Penta 5.7gi-b in an Aussie boat (Mustang) and after being stored over the Christmas break, the tacho doesn't work properly. If I tap it then the needle slowly rises but when I turn it off, it stays at the last known position. I can only guess what RPMs I'm doing based on the fuel flow meter and the sound of the engine.

My question is where do I start looking? Is it the gauge or if not, how does the engine 'talk' to the tacho? I know the speedo is via an air hose but I'm not sure if the tacho is by cable or some other mechanism and the boat isn't stored locally so I'm wanting a heads up on what tools to take when I have a look.

Thanks in advance!!

Kind Regards,

David.

Your tacho should have a brand name on the facia, see your local marine dealer he should have one on the shelf. They are quite easy to replace.

 

[winbasic]

Re: RPM Gauge - works when you tap it!

The good news - I can get a replacement tachometer
The bad news - it doesn't have the logo in the back of it which the other gauges on the dash have

Question: Is it possible to disassemble the new tacho and take the backing plate off the old one and put it on the new one or am I likely to end up with two dead tachos if I attempt this?

 

[Black as]

Re: RPM Gauge - works when you tap it!

The good news - I can get a replacement tachometer
The bad news - it doesn't have the logo in the back of it which the other gauges on the dash have

Question: Is it possible to disassemble the new tacho and take the backing plate off the old one and put it on the new one or am I likely to end up with two dead tachos if I attempt this?

If you feel confident do it, if not you may end up with 2 dead tachometer's