Dual-battery Dual-engine Wiring
Posted: Sat Aug 20, 2022 11:00 am
[Moved to SMALL BOAT ELECTRICAL for discussion from another forum.]
My 25-foot boat is rigged with twin Mercury 200-HP [two-stroke-power-cycle] EFI engines. In 2021 the left engine tachometer did not work.
The 12-Volt power on the boat is supplied by two batteries and ONE OFF-1-BOTH-2 primary power switch that allows me to select which battery to use and both engines charge the battery selected by the switch.
In 2022 the left engine [voltage] regulators [apparently there are more than one on each engine] were replaced with updated models.
On August 20, 2022 while underway, I noticed the left engine tachometer again did not work.
When I returned to port at engine idle speed the left engine tachometer began to work again. I noticed on a Garmin instrument that the battery voltage was 13.5-Volts rather than 14.2-Volts, and from that I deduced that it [something unidentified] is charging only one engine.
Then I opened the fuse box on the upper part of the engine that houses three fuses. I realized that one of the three fuses was not broken but was overheated. This is exactly what Mercury recommends to replace with the new model regulators from 20-Amperes to 30-Amperes.
I would not like to keep buying regulators and burning them all the time. I don't know if it's a coincidence but the problem happened while I was sailing with high waves and in any case the problem always appears in the left engine. Thank you.
My 25-foot boat is rigged with twin Mercury 200-HP [two-stroke-power-cycle] EFI engines. In 2021 the left engine tachometer did not work.
The 12-Volt power on the boat is supplied by two batteries and ONE OFF-1-BOTH-2 primary power switch that allows me to select which battery to use and both engines charge the battery selected by the switch.
In 2022 the left engine [voltage] regulators [apparently there are more than one on each engine] were replaced with updated models.
On August 20, 2022 while underway, I noticed the left engine tachometer again did not work.
When I returned to port at engine idle speed the left engine tachometer began to work again. I noticed on a Garmin instrument that the battery voltage was 13.5-Volts rather than 14.2-Volts, and from that I deduced that it [something unidentified] is charging only one engine.
Then I opened the fuse box on the upper part of the engine that houses three fuses. I realized that one of the three fuses was not broken but was overheated. This is exactly what Mercury recommends to replace with the new model regulators from 20-Amperes to 30-Amperes.
I would not like to keep buying regulators and burning them all the time. I don't know if it's a coincidence but the problem happened while I was sailing with high waves and in any case the problem always appears in the left engine. Thank you.