replace 20A fuse with circuit breaker?

[Home Cookin']

I am still going crazy with an untraceable short occassionally popping the little 20A fuse that covers the starter and PTT. Usually happens at high rpms and/or after running for a while.

If I give up trying to fix it, and replace the fuse with a 20A circuit breaker mounted somewhere accessible, I could just flip it back on. It doesn't affect the motor while it's running; just won't restart or tilt. I know that's not the best solution but I am at the end of my rope, and bottom of my budget. Any harm in it?

or if I attach a voltmeter/circuit tester to the fused line, what should I see? Constant current even if the motor is running (ie starter is off) and PTT is not being used? The line also operates the fuel guage. I thought I'd run it up to the point where it pops to see what happens.

1987 70 hp Johnson. I already replaced the controls and wiring harness--had it done professionally.

Thanks!

 

[Daviet]

Re: replace 20A fuse with circuit breaker?

Use an AMP meter in series in the line in place of the fuse, it will show the draw in the system. Operate the trim, engage starter, start moving wire harness watch the meter, if something draws more than 20 amps, thats your problem.
Do you have a service manual to trace the system with the fuse in it, if not it would be very helpful to troubleshoot the system.

 

[clanton]

Re: replace 20A fuse with circuit breaker?

I sometimes use a breaker to find wiring problems, have made up with pig tails that will connect to harness.Careful, look for hot wire, smoke. If you have a laser temp checker, you can find the hot spot in the harness. Dirty and loose connections will cause it to blow the fuse also.

 

[Home Cookin']

Re: replace 20A fuse with circuit breaker?

I have a digital multimeter; what is the best way to use it as an amp meter? Would that be the DCmA setting? (DCv, ACv, ->+ check, K(Ohm), DCmA, ACmA settings)

Since it seems to blow at high RPM's testing is difficult as i don't want to rev it up in Neutral--or would a quick test be OK for the motor?

I'll look for a service manual. The wiring harness on the engine is brand new.

thanks, all.

 

[tashasdaddy]

Re: replace 20A fuse with circuit breaker?

it would work. but won't keep you from melting wire from solenoid to breaker. i would seriously look at the tilt wiring, as you do use that when trimming, while the motor is running.

 

[Home Cookin']

Re: replace 20A fuse with circuit breaker?

thanks, T-daddy. Right now (I think) the fuse wire runs from the solonoid--but maybe from the black box on top of the motor, which I understand has something to do with the PTT.
As to the tilt wiring--not saying you're wrong--but the fuse blows when I am not touching anything--no starter, no PTT.
As I mentioned before I am detecting some light shock from the throttle handle if my hands are wet and I touch it and the steering wheel (SS). Someone suggested checking the ignition wiring for an arc; haven't gotten to it yet.

 

[daselbee]

Re: replace 20A fuse with circuit breaker?

Please understand that current measurements with a VOM will disable the overcurrent protection that the fuse normally provides. When you attach the meter into the circuit correctly for current measurements, all the current that is flowing in the circuit will go thru the meter. So, if for example, you have a short that will flow say (just a random number) 50 amps, the fuse would normally blow. But removing the fuse, and wiring in the meter, there is nothing to prevent the full 50 amps from flowing. You will burn up some wires, or the meter.

Just be careful. Also, most meters have a separate jack for measuring high currents. You unplug the positive lead and move it to a different jack. It will be labelled. Your meter's mAdc scale is for reading milliamps, which is way too low for your purposes. If you set the meter up in series at the normal fuse location, and put it on mAdc scale, you will blow the meter.

It is tricky, and you need to have a good understanding of meters and electrical circuits.

 

[daselbee]

Re: replace 20A fuse with circuit breaker?

An added thought...I usually wire in a 12v light bulb (automotive) in place of the fuse. When the short is present, that bulb will burn very bright. If no short exists, the bulb will not burn. The bulb provides the circuit protection (limits current) to prevent wires from burning up.

With the bulb in, you can wiggle wires, harness, push, probe...looking to find where it is intermittently shorting.....

 

[Home Cookin']

Re: replace 20A fuse with circuit breaker?

good idea on the light bulb; I can rig up a tester from some old stern lights I have laying around.
I had thought about the fact that bypassing the fuse with a meter removes the protection, exposing the meter and motor to damage. Best I could do is watch it closely and yank it if it moves up--which doesn't help if it's a spike. Of course, I can test it through the fuse, to see what happens just before it blows. I am obviously new to this side of eletrical work.
But does this help: When I'm running I know when the fuse has blown by my fule guage dropping to E. Just before it blows, the guage will sometimes move erratically. I am trying to observe all conditions to find the problem, and have accumulated a bushel basket full of blown fuses in the process! So instead of watching the guage I'll watch the light bulb.

 

[Al-53]

Re: replace 20A fuse with circuit breaker?

Have you checked for bad wires in the controller on the switch...or on the plugs from controller to engine harness...I had a bad wire on the engine harness..was brittle and cracked...blew my fuse a few times till i found it..sliced it heat-shrinked it over the splice and then used liquid tape over that to keep it from moisture and corrosion


the insulation on the wires seem to get brittle in age...

I am going to make a new engine harness this winter as a project..using my old red plug and better wire....

Al

 

[captk]

Re: replace 20A fuse with circuit breaker?

You might also pull the flywheel and check for frayed wires from the stator. Bill

 

[clanton]

Re: replace 20A fuse with circuit breaker?

If you are getting shock from control, repair this problem.

 

[Home Cookin']

Re: replace 20A fuse with circuit breaker?

so just to confirm, I check the amps with my multimeter on DC Amps and not AC Amps? Is everything DC on an outboard system?

thanks for the education, guys!