Blowing engine fuse after 2 seconds of cranking ‘78 Johnson 70hp.

Gday all
Weirdest thing. I am blowing the 20amp fuse near the starter solenoid everytime I crank the engine for 2 seconds. Cranking obviously then stops when the fuse blows. Fuse is ok with ignition on or off and with choke active. Fuse does not blow instant I start to crank, but blows after 2 seconds of cranking every time. Also if I bridge directly from +ve battery to active on the starter solenoid (replicating the starter switch bypassing the fuse) then can get the motor cranking and running, but will blow fuse in 30 seconds or so.
perplexed.

There is a bare wire in the harness from solenoid to the ignition switch.----Or from ignition switch back to the solenoid.-----Or internally in the solenoid.------Inspect entire length of wiring harness for signs of melting plastic.----At any time did you find a loose wiring connections /terminals ?

racerone said:

There is a bare wire in the harness from solenoid to the ignition switch.----Or from ignition switch back to the solenoid.-----Or internally in the solenoid.------Inspect entire length of wiring harness for signs of melting plastic.----At any time did you find a loose wiring connections /terminals ?

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I had the same thought at first. Except the OP's last sentence says it still blows the fuse while the motor is running after bypassing the solenoid (solenoid out of the picture now). Better concentrate on the run/accessory circuits for shorts/overloads. Any boat wiring or accessories improperly connected to the ignition switch?

Replaced a control box a few years ago.----Wiring harness from engine to control box showed signs ( melted insulation ) of overheating.-----The 12 volt supply from solenoid to key switch had a short.-----It is up to the owner to check the situation.-----Sometimes coaching on simple electrical stuff can be frustrating.

Thanks to all for the comments. Looks like some more fun ahead to solve the issue. Any thoughts on why there would be the 2 second delay in the fuse blowing? My experience with a short is the fuse will blow the instant the short circuit is closed.
also just a quick comment on the starter solenoid bridging. The bridge from +ve battery to active starter solenoid terminal would only be in place during cranking, once the engine fires up then that bridge is removed. The bridge is only to activate the starter motor.

Tortoise said:

Thanks to all for the comments. Looks like some more fun ahead to solve the issue. Any thoughts on why there would be the 2 second delay in the fuse blowing? My experience with a short is the fuse will blow the instant the short circuit is closed.
also just a quick comment on the starter solenoid bridging. The bridge from +ve battery to active starter solenoid terminal would only be in place during cranking, once the engine fires up then that bridge is removed. The bridge is only to activate the starter motor.

Click to expand...

Right, that's why I said what I did in post #3. Problem most likely is not in the starting circuit.

Thanks.

Gday
Just thought to close out this post with the cause. It was a neutral switch wire pinched (by me) between the remote control housing when I cleaned that out and put it back together. I am guessing that the delay in the problem coming to light and delay of 2-3 seconds for the fuse to blow could relate to the wire not being fully exposed to the housing metal…..

Also had a nifty fuse set up for trouble shooting.