3YM30 Tacho

[Tugalong]

My tacho in our R21EC ,which has a Yanmar 3YM30 engine, has gone crazy. The engine etc is only 3+ years old and has done about 80 hours.

After fitting a new starting battery the tacho now reads about 750 rpm high, it doesn't matter what speed it is supposed to be, it is consistently high.

Has anybody got any idea on what the problem maybe ?

Thanks :cry:

Geoff

 

[daviduphoff]

Perhaps it is related to the hour meter problem on my 21EC. I have posted about it before but never have gotten an answer. Sometimes it shows hours (currently about 875) and sometimes it is completely blank. It has done this ever since I bought the boat last July. I spoke to the PO about it and he said he never noticed the problem. I have never been able to narrow down what causes it.

I have had the local Yanmar service center located conveniently across the street from the marina where my 21 sleeps at night come over and look at it when there is no display. They too are perplexed. It does not matter what the RPMs are. One day it is blank and the next day it shows hours. Ambient temperature also has no bearing as far as we can tell. I think it has to do with how many beers are left in the fridge. The more beer there is the more likely it is to display hours. Perhaps this is just an excuse to keep the fridge stocked!

 

[Pearl]

David,
I had the same problem with the display. I think the hour meter runs off the ignition switch. I found a loose wire on the ignition switch and haven't had a problem with the display since. Good luck!

 

[Andrew Custis]

The tachometer on the R21EC for the Yanmar reads off the alternator to my knowledge. There is a plug on the alternator that could be corroded or not making perfect contact. You could also verify this by contacting Yanmar America as well. This engine has been around for a long time so it is also known by most of the Yanmar dealers around the US I would imagine.

 

[Stevan47]

Hi Geoff: Not sure if this might help with the diagnostics, but you might be iterested to know that my tacho does not always revert to 'zero' when I shut down the engine. This puzzled me a little. Whenever this happens, I just turn the key back to the ON position,very briefly, but not to START, then return it to the OFF position. The tacho needle then 'zeroes" out. Not sure what this means, but everything else is okay, so can't be too catstrophic. Just thought this might help - if not, no harm done. Still learning about my little R21. Regards, Stevan

 

[SGIDAVE]

Hi Geoff: Not sure if this might help with the diagnostics, but you might be iterested to know that my tacho does not always revert to 'zero' when I shut down the engine. This puzzled me a little. Whenever this happens, I just turn the key back to the ON position,very briefly, but not to START, then return it to the OFF position. The tacho needle then 'zeroes" out. Not sure what this means, but everything else is okay, so can't be too catstrophic. Just thought this might help - if not, no harm done. Still learning about my little R21. Regards, Stevan

My tach does that too.

david