Engines won't start

[NMerch]

I have a (new to me) 2002 Campion Allante LX925 with dual Volvo 5.0L GXIs.

They've been starting fine since I got the boat a few weeks ago but yesterday after being out and running for a couples hours we stopped at a bay for 30 mins or and when attempting to start I neither engine would start. There is a single click from (the solenoid engaging I believe) but no cranking.

Voltage at the batteries is good (12.7 on the starter batteries, and 6.1 on the house golf carts).

Boat is in neutral and there is no kill switch as far as I can tell.

It seems unlikely both starters or solenoids would die at the exact same time so I have to think it is something before that...

Here is a video of an attempt to start both engines:
https://youtu.be/AW90XdgGIeo

Anyone have any troubleshooting tips?

 

[Lepke]

Ain't electronic engines nice?
Make sure ground between battery and engine is clean and making good contact. You should have battery voltage where the cable connects to the starter. You should have 12v at the back of the key switch. The click could be a solenoid or another relay that powers the entire system.

If both engines won't turn either starter, then it's not the starter or solenoid.

With a helper, when trying to start, measure voltage at the start wire on the solenoid. Solenoid usually has 3 connections, 2 heavy duty posts and one small one. 1st post-battery cable, 2nd post-solenoid to starter, and a small wire that energizes the solenoid. With the key in the start position you should have 12 volts at the small wire terminal. No voltage-you have a problem somewhere in the start circuit.
If the engine is controlled by a computer module, it could be the module, connections or a sensor.

 

[porman]

Try turning the engines over by hand. A friend had a boat with a single Volvo 5.0L GXI and several times after shutting down he would get water in the cylinders from a poorly designed exhaust system, locking the engine up. The risers weren't high enough. He had to remove the spark plugs and turn it over to force the water out. Luckily no internal damage.

 

[C lectric]

Neither engine would crank.
Likely a poor ground connection at the engine battery.
There are other possibilities of course but when neither works yet batts. show good voltage
this becomes very likely.
Clean and retighten.

If that starts the engines then start a program to clean and tighten all battery connections.
This is routine mtce.