In Line Fuse's

[tannedman]

Ok where do i start. I bought a small bass boat last fall with a 75hp 3cyl Mec so far the starter won't even try engageing and the trim only works in the down position. I'm starting with the inline fuse's 3 of them were wrapped in foil and 1 was in peice's now i know there is 1 20amp? right near the starter now would it matter if i use all 20 amp fuse's or what size would i need as i can't make out what the other's were i'm guessing 5amp?

 

[Texasmark]

Re: In Line Fuse's

Let me walk your through it.

The 20 amp fuse near your starting solenoid runs all your Merc functions including your engine, remote control, and any Merc accessories (tach, speedo, fuel gauge) attached to the Merc accessory plug of your Merc wiring harness near your control box. It says 20 amps and that is what it needs to be.

Any other "stuff" is wired on it's own. I don't know about your foil wrapping nor why, but everything else needs to be:

10 Amp fuse for 16 AWG wire
15 .............for 14
20 .............for 12
40 .............for trolling motor wiring...usually 6 gauge.

If you don't know what AWG (American Wire Gauge) is, go to your automotive parts store and get into their wiring/connectors section and you can see the packages with wire in them with the AWG size on the label. Compare the size (diameter of the wire, forget the insulation) of that wire to yours and you now know how to size it.

You need a pretty much fully charged battery to crank your engine. If it is discharged, charge it then get after your engine starting. A clicking starting solenoid is a discharged battery.

Trim only working in the down only position could be a bad up trim relay. You have 3 relay/solenoids that look a lot alike: starter, up switch, down switch. There is a blue and green wire to the trim cylinder that applies activation voltage to the trim motor. Each comes from either the up or down relay (one color per relay).

The blue/white or green/white wires supply 12v from your trim button to activate the respective relay. When it energizes it runs the pump in the direction selected to move the piston out or in, up or down. If you have 12v to the xxx/white control wire to the respective relay, and you don't have 12v through the high current contacts, the relay is contaminated and needs to be replaced.

Want more ask.

Mark

 

[triumphrick]

Re: In Line Fuse's

Another reason those fuses can fail is the poor quality of the fuseholders. If not making really, really good contact with the fuses, they will draw more current and blow the fuse. After going thru all this, check spring tension, lightly sand ends contacting fuse or replace entirely. Good luck!

 

[Texasmark]

Re: In Line Fuse's

Another reason those fuses can fail is the poor quality of the fuseholders. If not making really, really good contact with the fuses, they will draw more current and blow the fuse. After going thru all this, check spring tension, lightly sand ends contacting fuse or replace entirely. Good luck!

All due respect man, but it's not additional current: The load determines the current, not the wiring, nor the fuse. What pops the fuse in the situation mentioned is heat from a bad termination in that the fuse can't differentiate between wiring over current heat and heat caused by excessive terminal resistance. To the fuse, heat is heat and heat is what melts the metallic conductor of the fuse and blows it. It has no earthly idea as to where the heat came from and doesn't really care. Big grin.

Agree, clean up the contacts then contact resistance will diminish, voltage drop across the contacts will diminish, heat will decrease and life will be good until you get a real life overload.

Mark

 

[j_martin]

Re: In Line Fuse's

I replace inline barrel type fuse holders with these. 10,15, 20, and 30 amp, different size wires.

 

[triumphrick]

Re: In Line Fuse's

All due respect man, but it's not additional current: The load determines the current, not the wiring, nor the fuse. What pops the fuse in the situation mentioned is heat from a bad termination in that the fuse can't differentiate between wiring over current heat and heat caused by excessive terminal resistance. To the fuse, heat is heat and heat is what melts the metallic conductor of the fuse and blows it. It has no earthly idea as to where the heat came from and doesn't really care. Big grin.

Agree, clean up the contacts then contact resistance will diminish, voltage drop across the contacts will diminish, heat will decrease and life will be good until you get a real life overload.

Mark

Sorry to disagree, but I don't buy your analogy. Heat is a byproduct of the higher current. The basic design of the fuse is the soldered element will fail when the amount of current it is rated for increases and heat is THEN generated. Just as it is designed. The voltage drop across that faulty connector varies, and WILL produce increased current. Consequently your heat. Consequently your blown fuse.

Try an experiment. With a full load on a circuit, intermittently connect the fuse to the fuse holder. That intermittent contact will cause the current to vary, eventually exceeding the amount needed to generate the heat required to blow the fuse. That heat is the direct result of the current flowing through the fuse.

 

[tannedman]

Re: In Line Fuse's

Thanks guys i will try and clean the fuse conecters if that don't work i will then replace those too. I did try a fully charged battery and still just clicking. Possible relay or silinoid problem?

 

[CharlieB]

Re: In Line Fuse's

Poor battery cable connections, on EITHER end of the cable, will contribute to a 'just clicking' condition as the poor connection will not allow adequate voltage/current to run the starter.

Also remember to clean the contacts of the short cable between the starter relay and the starter motor.

You may try using a set of 'jumper cables' across the starter relay as a crude test for poor contacts in the relay.

 

[Texasmark]

Re: In Line Fuse's

Sorry to disagree, but I don't buy your analogy. Heat is a byproduct of the higher current. The basic design of the fuse is the soldered element will fail when the amount of current it is rated for increases and heat is THEN generated. Just as it is designed. The voltage drop across that faulty connector varies, and WILL produce increased current. Consequently your heat. Consequently your blown fuse.

Try an experiment. With a full load on a circuit, intermittently connect the fuse to the fuse holder. That intermittent contact will cause the current to vary, eventually exceeding the amount needed to generate the heat required to blow the fuse. That heat is the direct result of the current flowing through the fuse.

You can send me a PM on this if you want to continue. I hope no one reads and accepts your reply.

Mark

 

[j_martin]

Re: In Line Fuse's

Sorry to disagree, but I don't buy your analogy. Heat is a byproduct of the higher current. The basic design of the fuse is the soldered element will fail when the amount of current it is rated for increases and heat is THEN generated. Just as it is designed. The voltage drop across that faulty connector varies, and WILL produce increased current. Consequently your heat. Consequently your blown fuse.

Try an experiment. With a full load on a circuit, intermittently connect the fuse to the fuse holder. That intermittent contact will cause the current to vary, eventually exceeding the amount needed to generate the heat required to blow the fuse. That heat is the direct result of the current flowing through the fuse.

Where you getting the good stuff?

For everybody else:
A fuse is a low melting point, resistive element (fairly low resistance) that heats up when current flows through it. It is rated in current flow, which is that current that will develop the voltage drop, (usually a few millivolts) and heat that will melt the element and open the circuit.

If a connector is dirty, it now has a significant amount of resistance, will develop a voltage drop, generate heat, which then transfers through the fuse connectors (caps) to the element and melts it. The current actually goes down as this is happening.

A 3AG fuse will normally blow in the middle of the fuse wire if it's overloaded, and usually blow up inside the end cap, sometimes not easy to see if the connectors are overheating. Key word is usually.

BTW, I've been an electronics tech or engineer for 45 years.

hope it helps
John