bf 135 tachometer fluxuating

#1 (**permalink**) 04-01-2009, 05:56 PM

I have twin 2005 bf-135`s on my boat. Last year the 1/8" water pressure reference line on one of the engines had a split in it and it poured salt water into my altenator. The altenator was beyond fixing so I replaced it. Since than the tachometer has been fluxuating from working correctly to drifting from 1000 to 5,000 rpm`s when I'm at idle. It also acts up under load at other rpm ranges as well. The engine runs and sounds fine. Any ideas where I can begin to look ? Thanks Harry

boats.net · #2 (**permalink**) 04-02-2009, 09:15 AM

Thats usually a bad tach, you can monitor the AC voltage at gray wire at back of tach to see if signal voltage is constant.

#3 (**permalink**) 04-02-2009, 10:02 AM

Thanks, I will do this next week after I pick the boat up from winter storage and advise. However, I do have a followup question before I try that. When I monitor ac voltage of gray wire, what should voltage range be, and which color wire is the common, or are there only two wires ?

thanks,

Harry

boats.net · #4 (**permalink**) 04-02-2009, 05:01 PM

Check between gray wire and black wire, you are looking for voltage to increase as rpm's increase but remain steady with rpm's.