Mercruiser engine alarm issue

[Team PCBeach]

2003 360 Sundancer with twin 8.1 Mercruisers. Went to run the boat today for the first time in two months (busy selling and buying a house). This was the first time we were running the boat after the marina had installed our rebuilt generator, which required removing the STBD exhaust. When I activate the start buttons for both engines, the Mercruiser engine alarm goes off constant, even though I have not started the engines. If I only energise one engine, the alarm does not go off. Even stranger, sometimes I can get both started with no alarm, but the constant alarm starts within 5 minutes. If I turn an engine off (doesn't matter which one) the alarm stops. Vessel View and gauges show oil pressure, water pressure, water temp and battery voltage normal in both engines when running. Fuel is low 24 gal STBD, 39 gal PORT, but I don't think the alarm sounds for that. Anyone have any suggestions?

 

[Seapig]

Are you sure battery voltage doesn’t drop very low while cranking ?

 

[Mark Searay]

Try ruling fuel out by just topping up

 

[Team PCBeach]

Are you sure battery voltage doesn’t drop very low while cranking ?

I don't think it is battery because the alarm usually (but not always) happens before I even try to crank.

 

[Team PCBeach]

Try ruling fuel out by just topping up

That was what I was going to do today, head to the fuel dock before we took a short ride. Unfortunately with the alarm, I didn't even leave the dock since I didn't know what was causing the alarm.