Yanmar 1GM tach problem?

[mwrohde]

All -

I've got an old Yanmar 1GM that has never, according to the tach, reach full RPM. I've not been able to find a reason for it, but have come to terms with it and run the engine at an RPM that provides suitable performance at a minimum of vibration.

Over the weekend it wouldn't reach my normal operating RPM. However, at an RPM that sounded good and /felt/ just like my normal RPM the boat cruised at the old normal speed.

So, the question is, can the tach fail a little bit at a time? I'm quite sure that even though the tach didn't show it the engine was running at very close the same RPM that it always has.

[lbdavis]

Bad tachs seem to be an issue with all Yanmars. My 2GMF has them. Search the G&M forum for this and you'll find several threads concerning Yanmar tach issues.

And let me know if you solve your problems. I'm still looking for a solution!

[Sapperwhite]

Every once in a while I have to clean the connections at the tach sender and make sure the fitting is tight....hey look at that, my rpms are back! Clean and tight electrical connections work for me. I also keep a spare tach sender in my spares for the day it finally craps out. Mine is a 2GM btw.