Funny Electrical problem
 

I recently purchased a Manta 40 (catamaran). It has two Volvo Penta MD2030 engines. If one engine is started, the tachometer for that engine runs properly (either engine). When both engines are running, the port engine tachometer stops. The previous owner reported that the problem started when the alternaters were upgraded to 120 amp alternaters. Any thoughts or suggestions as to what is causing the problem and how to correct it would be greatly appreciated.

Thanks

Bruce

Funny Electrical problem
 

Well over 90% of these kinds of problems are bad or improper common connection. I would look of the common side of the connection I an almost 100% sure that is where you will find the trouble.

Funny Electrical problem
 

Thanks for the information. This should help me in getting the boat ready for the next sailing season.