Tachometer Problem

k9th · Post by **k9th** » Mon Sep 05, 2011 6:45 pm

Saturday when I started the engines on my tri-cabin I noticed something strange that I had never noticed before. The starboard engine was already running at 1,400RPM and when I engaged the starter to start the port engine the starboard tachometer began to jump all over the place. I shut the start switch off before the engine started and did it again just to see if it would repeat and it did. I did it two more times with the same result. Once I started the port engine the starboard tach settled back at 1,400RPM. The engine starters are connected to two separate batteries so there shouldn't be any connection that way.

Any ideas on what's happening here?

Big D · Post by **Big D** » Mon Sep 05, 2011 8:35 pm

Is there a sync gauge or display? It would be the common denominator in what you are otherwise describing as two isolated circuits. Sometimes tachs are also affected by other signals as well. Do you have a battery isolator hookd up to the two engine battery banks? Could also be just a bad connection at the gauges, wiring, engine plug, coil etc. Also, the selector on the back of the tach for setting number of cylinders; take it and rotate it back and forth several times. The contacts corrode inside and cause funny readings.

alexander38 · Post by **alexander38** » Mon Sep 05, 2011 8:39 pm

check the ground to your synchronizer. add the same trouble at the start of the season..

k9th · Post by **k9th** » Mon Sep 05, 2011 8:43 pm

Thanks for the tips and ideas. I will check them next weekend when at the marina.

alexander38 · Post by **alexander38** » Mon Sep 05, 2011 9:02 pm

what Big D said is so true to, just a sharp hit can change those switches some times

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