Entire electrical system dies when under way

[peters715]

I wasn't clear, apologies. Reviewing the Mercruiser Service Manual 1, there is no reference to a circuit breaker.

The manual covers 1963-1973, my Mercruiser being a 1969.

That is an old picture. The power cable is brand new and all connectors are bright and clean.

 

[99yam40]

does this happen every time you hit the T&T?
Or only while underway?
I would be checking to see how much current the T&T pulls and what the voltage drops to on everything while the T&T unit is running

 

[peters715]

does this happen every time you hit the T&T?
Or only while underway?
I would be checking to see how much current the T&T pulls and what the voltage drops to on everything while the T&T unit is running

After replacing battery cables and battery switch I am not experiencing the problem now. I can run the trim, blower and sump pump without any issues.

But my alternator now seems to be acting up. When I start the engine the volt meter shows +12.5~ for a bit and then drops to zero. So break out the multi meter and start checking voltages.

 

[99yam40]

You need to monitor the battery voltage and the voltage at different places before starting and after.
with motor running you should be reading over 12.5VDC probably around 13.5 or 14

I do not believe the battery voltage your gauge shows is correct if it goes to 0 and RPMs drop
I was wrong it was the bilge pump that you said it affects the systems

"The alternator output drops and engine rpms drop (probably less than 50 RPM) when I turn on the bilge pump, system doesn't die, but it's noticeable."