size of fuse

[mollycat]

I have a '93 Mariner Stalker 28 but am not sure what size of fuse to use. The motor stopped working and when I traced it back, it was the fuse, 30 amp. It didn't blow but heated up and melted to the fuse holder. The motor was wired to the crank battery. I think I will buy a deepcycle and place it in the bow, close to the motor.

 

[Ralph 123]

Re: size of fuse

The fuse should have blown long before the thing heated up to the point of melting! This is how fires start.<br /><br />1) Was this fuse put in w/o knowing what fuse was meant to be there or is this the fuse it is designed for?<br /><br />2) What's on the circuit and what is the total current draw?<br /><br />3) What gauge wire is used throughout the circuit?<br /><br />Don't be surprised if the wiring is burnt somewhere in the run. You may have to replace it. Inspect it and look for melted insulator.

 

[denniz]

Re: size of fuse

40 amp 12 v 50 amp 24v\

 

[Ralph 123]

Re: size of fuse

If that's the case (takes a 40A), Then:<br /><br />1) could the circuit have been drawing less than 30A but still have heated the fuse up to the point where it melted the holder? That can sure happen if your fuse it too big for the circuit but in your case it was too small.<br /><br />2) is the fuse defective and was the circuit actually drawing over 30A?<br /><br />3) Is the fuse holder under-rated for the circuit it is being used in? <br /><br />mollycat, how comfortbale are you with troubleshooting this? If I were you, I would be concerend until I got to the bottom of this. Safety 1st, 2nd and 3rd. I wouldn't simply stick a 40A in there and move on until I understood what happened and that it was safe to do so. JMHO

 

[SingleShot]

Re: size of fuse

Formost you need to determine the wire size of the circuit. Fuses/cb's are for thermal protecting not only the devices but the wire. As stated above, this is how fires start. If the wire is rated for 20amp and you have a fuse protecting at 30 you will toast the wire big time if the circuit starts drawing this type of current. A direct short will blow the fuse and trip the breaker. The fault current allowed to flow during the short is pretty small with automotive type fuses so this is not a problem. As these fuses are not typicaly designed for steep inrush currents.<br /><br />SingleShot

 

[mollycat]

Re: size of fuse

Thanks for all the info. I will use all this information to get to the bottom of the matter, Safety first.

 

[Paul Moir]

Re: size of fuse

One other possiblility - since the fuse holder is a connection point, any corrosion will bring up resistance and so cause heat when current flows. I've seen this one happen a few times, but never on a boat. It's pretty gross when a protection device itself fails unsafely.<br />I would look at any other fuse holders in the area very carefully.

 

[enriquepagan]

Re: size of fuse

In many/most case's i have seen this happen, its caused due too the Fuse holder being rusted and inproper connection cause ARCHing which in turn cause's sparking and heating for the casing.<br /><br />But do check out all the other info the other gentleman have placed here. It will save you time many but most important maybe your life......... Happy boating.