Kevin,

I have a Johnson 150 Fast Strike engine. The fuse in the engine is blowing. What could be the problem?
Background

Last year I installed a sump and it shorted out – several of the wires’ insulation melted. I have replaced or repaired all I could find. The motor ran well after the repairs, so I thought I got all of them.

This year I have run the motor on several occasions and it ran well. However, now fuse in the engine compartment is blowing shortly after the engine stars up.

Second Question

During the process of troubleshooting I had to remove the fuses. I forgot to write down which fuse goes to whicn component.

My fuses are:

Navigation lights
Internal lights
Sump pump
Bilge pump
Auxiliary (radio)
Auxillary

Jim

Jim,

The fuse on the engine supplies power to the ignition switch and engine trim control on your shifter. It also provides power for your gauges through the ignition switch.

Have you added extra devices to this circuit? The fuse blowing shortly after starting could a short in the boat wiring that occurs only when the engine is vibrating or the system draws too much current when the voltage increase as the engine alternator begins to charge the system.

Short:

Trace the red/purple wire from the engine to your key switch. Also trace the purple wire from the ignition, through your gauges, and back to the engine. A short in this wire will cause the problem.

Too much current draw:

Remove all non-essential wires from the ignition circuit. You only need red/purple from engine to key and purple from key to engine to run the engine.

If the fuse still blows, there is something wrong with the engine electronics that is causing the fuse to blow.

If the fuse doesn’t blow, the problem is with one of the non-essential items connected to the ignition switch. Eliminate these one at a time. This may take some time. It could be something as easy as a shorted wire behind a trim gauge or as difficult as a tachometer that shorts out at 3,000 rpms.

Fuses:

What size fuses do you have? What are the model/manufacturer of all the devices on your boat?

Hope this helps,

Kevin