1993 48HP Evinrude - Fuse Blowing

[ALATOM]

1993 48 hp Evinrude - The engine cranks and runs when first put in the water. When starting out I trim the motor and drive boat for a while and shut the engine off. Engine will not restart and a fuse will be blown. After changing the fuse engine starts and runs fine. If the power trim switch is actuated the motor will continue to run but the next time I try to start the motor the fuse will be blown. Change the fuse and the engine cranks and runs. Take the boat out of the water for a few days and put it back in and it works fine for a while then the fuse blows.

Power trim works fine and will not blow a fuse while the engine is not running. I removed the power trim and immersed it in water to see if the motor was getting wet and it works fine under water. The rear trim switch is ok.
I can't find a short in any of the wiring and all connections are tight. i have not disassembled the shift assembly yet. Could there be a problem with the ignition switch or the trim switch in the shifter.

Does anyone have an idea what the problem may be.

 

[Crosbyman]

Re: 1993 48HP Evinrude - Fuse Blowing

try an get a ammeter in series with the fuse circuit... measure the current during operation or at least try to notice when it peaks and blows the fuse.

It may clue you as to what event (component) suddenly draws to much current.

If the ammperage is to high to start with in a steady idle state then something is pulling to much amperage. Try and locate which component

You may be just on the edge of blowing the fuse and suddenly a few more amps does it. Try to identfy the event/component

(you can try to hook-in a 40-50 watt 12 v bulb instead of a fuse. Watch the light when it suddenly flares up... indicating a sudden pull of amperage. the bulb will act as a ballast resistor keeping the current within reason ( its own amperage needs).

In a worst case scenario a sudden zero resistance load (short) from the culprit component will only " turn on the bulb" to its rated wattage.

In the telephone industry years ago ballast lamps were used to replace fuses. Anytime a central office componet would "short out" the bulb would simply light up until the problem or defective component was fixed up.

( I presume the fuses you are using are according to the expected load....ie:. use the proeper fuse for the application.


edit: keep in mind that the bulb will act as a current limiter and lowers the working voltage on the trim motors. components may not work properly . the bulb only serves temporariliy to clue you visually as to current drawn. It is just a tool. use it sparingly if you do go that way. The ammeter is the preferred method of course. it does not affect working voltages. Up to you to decide. Do not run for extensive perodes with the bulb (resistor) in series in the fuse circuit !!

 

[racerone]

Re: 1993 48HP Evinrude - Fuse Blowing

Look for issues ( bare wires / pinched wires ) on the trim and tilt system.-----------Are any accessories hooked up to the motor electrical cable ?--Are ground connections confirmed clean and tight ?----------Wing nuts on battery or nylock nuts ?

 

[ALATOM]

Re: 1993 48HP Evinrude - Fuse Blowing

try an get a ammeter in series with the fuse circuit... measure the current during operation or at least try to notice when it peaks and blows the fuse.

It may clue you as to what event (component) suddenly draws to much current.

If the ammperage is to high to start with in a steady idle state then something is pulling to much amperage. Try and locate which component

You may be just on the edge of blowing the fuse and suddenly a few more amps does it. Try to identfy the event/component

(you can try to hook-in a 40-50 watt 12 v bulb instead of a fuse. Watch the light when it suddenly flares up... indicating a sudden pull of amperage. the bulb will act as a ballast resistor keeping the current within reason ( its own amperage needs).

In a worst case scenario a sudden zero resistance load (short) from the culprit component will only " turn on the bulb" to its rated wattage.

In the telephone industry years ago ballast lamps were used to replace fuses. Anytime a central office componet would "short out" the bulb would simply light up until the problem or defective component was fixed up.

( I presume the fuses you are using are according to the expected load....ie:. use the proeper fuse for the application.


edit: keep in mind that the bulb will act as a current limiter and lowers the working voltage on the trim motors. components may not work properly . the bulb only serves temporariliy to clue you visually as to current drawn. It is just a tool. use it sparingly if you do go that way. The ammeter is the preferred method of course. it does not affect working voltages. Up to you to decide. Do not run for extensive perodes with the bulb (resistor) in series in the fuse circuit !!

Thanks. I have an amp meter and will try that first. I checked the amperage with the trim unit on a bench and it was only 1.2 amps. I will install the unit and test it under load.

 

[ALATOM]

Re: 1993 48HP Evinrude - Fuse Blowing

Thanks. I have an amp meter and will try that first. I checked the amperage with the trim unit on a bench and it was only 1.2 amps. I will install the unit and test it under load.

The only other circuit on the cranking battery is the depth finder, bilge pump, and running lights. All wiring is new and all connections are tight. Tonight I will inspect the switches in the shifter.

 

[sutor623]

Re: 1993 48HP Evinrude - Fuse Blowing

You can sometimes find a short to ground if you run the motor in the dark. Just an idea. Not saying that you def. have a short, but it sure is possible.

 

[Fed]

Re: 1993 48HP Evinrude - Fuse Blowing

Are you using the correct size fuse?

 

[ALATOM]

Re: 1993 48HP Evinrude - Fuse Blowing

Are you using the correct size fuse?

I am making progress on checking wiring. last night I disassembled and inspected wiring in shift unit and found no problems
Removed shrink tubing from wires coming out of power trim motor and found a bare spot. I don't know how it could affect the circuit since it was protected by the shrink tube unless there is a catalytic effect grounding to the motor while under water.

I will repair it tonight and inspect the rest of the wiring.

 

[ALATOM]

Re: 1993 48HP Evinrude - Fuse Blowing

I am making progress on checking wiring. last night I disassembled and inspected wiring in shift unit and found no problems
Removed shrink tubing from wires coming out of power trim motor and found a bare spot. I don't know how it could affect the circuit since it was protected by the shrink tube unless there is a catalytic effect grounding to the motor while under water.

I will repair it tonight and inspect the rest of the wiring.

 

[Crosbyman]

Re: 1993 48HP Evinrude - Fuse Blowing

if you check the current with your ammeter use it in series with the fuse otherwise you will loose that protection.

The ammeter will let all the current fly by and it may cause component failures.
(some meters have internal fuses but do not rely on it . just measure current in series with your exixting , properly rated fuse.

 

[ALATOM]

Re: 1993 48HP Evinrude - Fuse Blowing

if you check the current with your ammeter use it in series with the fuse otherwise you will loose that protection.

The ammeter will let all the current fly by and it may cause component failures.
(some meters have internal fuses but do not rely on it . just measure current in series with your exixting , properly rated fuse.

Thanks for the information.

I think i solved the problem. One of the trim motor leads had a bare spot. probably from a pinch when the engine trims up and down. The wire had come out of the bracket that holds it in place. The two motor leads are covered with heat shrink tubing. When i removed the shrink tubing i found the bare wire.
I repaired the bare wire and installed new heat shrink tubing and reassembled being careful to make sure the wires were secure.
I ran the engine on the trailer for about half an hour, trimming up and down.
No blown fuse.
The real test will be when i put the boat in the water. Hopefully this weekend.
Thanks to all who have assisted with trouble shooting this problem.