Trouble Starting & Tripping Electrics?

[_jp]

Hi All,

2006 (ish) 4.3L Mercruiser with Carb and Thunderbolt Ignition

Boat was running great last year. Just attempted to start the boat for the first time this season (on earmuffs water hookup). It turned over a few times sounding normal, then the electrics went dead. Nothing on the ignition and nothing else (blower, etc). All fuzes are OK under boat dashboard and the 50 amp breaker mounted on the top of the engine was ok.

I bridged the starter motor "block" fuze (A - B) in the image below, and the blower worked. Then all the electrics came back on. Attempted several restarts and the same thing keeps happening, attempts to turn over, then electrics go and need to bridge the "block" fuze (I forget the official name of the block fuze) to bring them all back on.

- battery is brand this week, fully charged yesterday and fitted today
- block fuze was changed last year

Is this likely to be a faulty "block" fuze, or could it be a problem with starter motor perhaps?

Any pointers would be great, thanks

James

 

[Bt Doctur]

Not so much as how the factory has it wired.The block will fail if the alt goes bad or the output post is shorted to ground. Get yourself a "Maxi-Fuse and holder (50-60 amp is sufficient) and crimp on the correct size connectors and only protect the Orange alt feed wire, Wire the Red system power directly because the system is protected by the 50Abreaker,
Wired this way you only lose the charging system but not the the main power to the boat.

 

[_jp]

Not so much as how the factory has it wired.The block will fail if the alt goes bad or the output post is shorted to ground. Get yourself a "Maxi-Fuse and holder (50-60 amp is sufficient) and crimp on the correct size connectors and only protect the Orange alt feed wire, Wire the Red system power directly because the system is protected by the 50Abreaker,
Wired this way you only lose the charging system but not the the main power to the boat.

Hi, thanks for the quick reply. Just to check, are you saying that I have it wired up wrong on mine, or that they're all wired up this way from the factory and there's a better way?

What would cause the electrics to trip, is the block fuze "thermal protected", as i can get it working again after waiting sometime and then bridging it for a few seconds. Then it all functions again.

I'm happy to look into your solution regarding the maxi-fuse, as having this happen on the water would be a nightmare, but I am puzzled by what's likely to be causing it

Many thanks

 

[Bt Doctur]

hard to tell exactly why the 90 or 110A fuse stopped working , can blow a 90 with a 50 backing it up. A suggested rewiring it with the Maxi because the fuse can be easily changed if the issue is with the alt or its wiring, This way you still retain the ships main power to run the motor. Some call it a "lawyers fuse" but early years never had on the wiring.

 

[Droid]

I'm assuming the 2 cables on "A" are battery direct & trim pump.
"B"is alternator (orange) & all the electrical system.
Why did the black fuse blow (twice now if I read correctly) IDK. It's 90 amps & I can't see it blowing unless you have a huge short.