25 horse caught fire!

[renelson]

I've got a 98 model 25 hp 2 cylinder electric start tiller motor. Yesterday I backed it in the water and pushed the starter button and the button didn't reset - it stayed depressed. I then saw that the bare ground "cable" that goes from one of the starter bracket nuts to the screw by the gas line intake was red hot. It then caught a wire on fire and I had flames. I was able to put it out quickly thank goodness. The small ground cable had burnt in two.

Got home today and made another ground cable. After a few seconds of cranking, the cable continues to get red hot. Also, I noticed that the starter button didn't spring back out once I pushed it the last time. Looks like it had come out of its seat inside the cowling again even after I thought I had fixed it.

Could this be a bad battery? Could it be that the worn out ignition switch is causing it to get hot? I have no idea what's going on!!! Please help.

 

[Bob_VT]

Re: 25 horse caught fire!

You have corroded wires both + and - and I am willing to bet the corrosion is inside the insulation. When a wire corrodes on the inside the resistance goes WAY up and the cables get HOT. Every connection needs to be removed cleaned and replaced and I would have new heavy duty batter cables made.

I have been down a similar road but not with a fire......but I have seen red hot leads before.

 

[GA_Boater]

Re: 25 horse caught fire!

I would say the battery is good, it has enough juice overheat the ground wire. Was the motor turning over with the E-start? And if it was turning over, how long was the starter cranking before the smoke?

For some reason the starter is drawing too much current, hence the red hot wire. I would replace the start switch to begin with so the power is cut off when released.

 

[nwcove]

Re: 25 horse caught fire!

...isnt there a fuse in the mix?

 

[renelson]

Re: 25 horse caught fire!

Bob, thanks. I plan to get new cables and ignition switch.

GA, thanks. It wasn't cranking very long when it caught fire, but the switch was in pieces and it was basically engaging on and off as the motor vibrated. So it was giving juice to the starter on and off really fast. Think that's what caused the ground to get hot. Today the switch is back together, but it only engages the starter every other try. The times it doesn't engage the starter, it clicks audibly and the ground wire immediately gets hot. The times it does engage the starter, it still gets hot, but not near as fast.

Cove, no fuse in the mix. Maybe there should be??

 

[GA_Boater]

Re: 25 horse caught fire!

Is the click you hear the solenoid closing? You really need a new switch. Have you looked at the starter and does it turn freely? Bob is on to something with the corroded wiring.

 

[renelson]

Re: 25 horse caught fire!

Thanks guys. I think you are spot on with the switch. I let everything cool and came out to try again. I notice that when I don't push the switch hard, the wire gets hot, when I press the switch really hard, it doesn't. I don't know much about circuits, but I guess it isn't getting a very good connection and so it is getting hot. Would that cause the problem?

 

[Fed]

Re: 25 horse caught fire!

You need to find out why the starter motor case isn't electrically connected to the battery negative via the engine block then the main battery negative cable.

The small ground strap isn't there to carry the starter motor current.

 

[GA_Boater]

Re: 25 horse caught fire!

^^^^^ Now that's a great point, Fed. My negative battery cable goes right to the side of the starter.

 

[renelson]

Re: 25 horse caught fire!

Fed, good point. It all kinda makes sense now... Lol. I do have a ground wire running from the same bolt on the starter as the cable strap. It is running back to the neg battery post. I could slightly move the neg terminal on the battery. It's also got a bunch of other wires that are grounded on the negative terminal with it. My guess is that the ground was not connected well on the battery. I will pull them off and sand them down to ensure a good connection.

Still going to but a new switch.

 

[renelson]

Re: 25 horse caught fire!

I also noticed that the was a small bit of insulation missing from the ground wire back to the battery. It was where the strap got hot and melted it a little. I can see about a 1/4" of copper exposed.

 

[renelson]

Re: 25 horse caught fire!

I still don't understand why the heck the grounding strap is grounded back to the battery. It's just a static electricity relief for the area where the gas line hooks to the side of the lower cowling.

How the heck is the side of the motor grounded to the negative pole of the battery??

 

[Fed]

Re: 25 horse caught fire!

Alloy boat with hull connected to battery negative?

It's hard to see your set up clearly from here.

 

[renelson]

Re: 25 horse caught fire!

Okay, so I replaced the button ignition switch located on the lower cowling. That fixed the problem.

The problem was that the switch was shorting out on the aluminum lower motor cowling. Once shorted out to the cowling, the current was going through the cowling, into the static relief strap on that goes from the cowling (where the fuel line hooks up) to the negative post of the battery, and then of course back to the negative post of the battery. Once the old switch was replaced, the short was fixed and everything was right with the world...

Thanks to all for the help!

EDIT: By the way, that stinking switch was 60 bucks....oh well, at least I didn't pay for a boat mechanic to fix it....