tachometer

[Bob Middleton]

I recently bought a Catalina 27. The tachometer at first did not show RPM until the engine went above 1000. This was still okay as I usually ran in the higher range. Now, even though I change the RPM in the zero to 2200 range the tachometer fails to reliably follow the speed change. For example it "eventually" falls to zero when I go to neutral but very slowly. I doubt the signal from the alternator is at fault and supect the meter itself. Any suggestions? Where to buy a new meter if necessary? Thanks, Bob

 

[Randy]

Tachometer failure

Some tachometers read a signal from the alternator, others read the teeth on the flywheel. Your actual setup depends on your tachometer. An experienced engine mechanic can help diagnose this. Sorry I couldn't offer mroe help.Randy

 

[Hans]

Hi,If the alternator signal were at fault, your tach would under-read. Get a new tach at any of the popular boat suppliers like West Marine or Boat US - make sure to gety a Diesel tach (lower RPM range as compared to gas engines). You will have to set a selector switch on the back of the tach to reflect the number of poles (alterator) and the circumference ratio of pulleys - this is usually well described in the leaflet for your new tach. Should you have a 51A Prestolite alternator, the number of poles is 16.Quite likely, you can transfer the switch setting of your old to your new tach. You will find the replacement easy.PS: it is normal for the tach to start showing RPM only when the first engine exceed 1000 - your alternator needs a minimum initial speed to start producing output (self-exciting)Good luck,Hans