Fuse Blowing when trying to start inboard diesel

[lenseman]

. . . . . - didn't they have a fuse in the bilge pump supply? . . . . . .

As said above:

As the wiring got hot, and before it tripped out its own fuse, it melted into and shorted together all the other wiring in the major loom,

 

[pvb]

As said above:

As the wiring got hot, and before it tripped out its own fuse, it melted into and shorted together all the other wiring in the major loom,

So it was incorrectly fused?

 

[pvb]

Thanks for all your messages yes boat has worked fine previously with the 150amps fuse, only now i have the problem and have no idear why, Im getting down to the boat in the morning to do some checks, Hoping to try get done myself even though wires/electrics is not my strong point.

There's obviously another problem then, and hopefully you'll soon sort it out.

I'm a big believer in fusing battery circuits - the potential energy in the event of a short circuit is immense. The cabling from both my starter battery and my domestic bank is fused by MegaFuses, which are robust and reliable.

 

[yachtorion]

As said above:

As the wiring got hot, and before it tripped out its own fuse, it melted into and shorted together all the other wiring in the major loom,

Aw sorry misread it. In that case... what PVB said.

So it was incorrectly fused?

 

[lenseman]

So it was incorrectly fused?

I don't believe so, the fuse was a resettable type installed in the mid to late 1990's and carried the correct rating. As these fuses tend to be fit and forget, I don't know anyone who actually checks whether the current rating written on the side of the unit is true. You would need a high current variable resistor (reostat) and an high current ammeter inline to check when it trips.

How regularly would this test need to be conducted, annually??

I suppose the actual tripping mechanism inside the fuse became tired?

 

[pvb]

I don't believe so, the fuse was a resettable type installed in the mid to late 1990's and carried the correct rating. As these fuses tend to be fit and forget, I don't know anyone who actually checks whether the current rating written on the side of the unit is true. You would need a high current variable resistor (reostat) and an high current ammeter inline to check when it trips.

How regularly would this test need to be conducted, annually??

I suppose the actual tripping mechanism inside the fuse became tired?

The fuse might have been the correct rating for the bilge pump, but the purpose of fuses is to protect cable, so it would seem that the cable was under-specified.

 

[ex-Gladys]

I had a very mini one of these incidents last year when I "let the smoke out of the wires" and as we all know it's the smoke that gets electrickery working... Previous owner had wired a 12V 15A socket off the engine run relay which was only using a bit of 0.25sq mm at best to send the signal to the engine hr meter. The insulation melted big time, and only when the engine ran did I notice that the wire had run around the oilpressure gauge pipe... Nice little oil gusher...

 

[Eastanglian87]

Thanks all for your help, Got the electrician down today whom said that the 150amp fuse in the main fuse panel was too small so has put a bigger fuse in and it has not blown whilst trying to start however starting a new thread if anyone can help regarding what i hope to be the last part of my problem before i can get up and running regarding fuel blockage.