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Blowing fuses

J

j trex

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New to the forum this is my first post. My son an law has a 1976 75 Hp evinrude will start and run good when he stop to fish and try to restart to move to another place the 20 amp fuse on top of the motor is blown, he thinks its coming from running the motor wide open, he had it to a shop and the man couldn't figure it out any help would be appreciated
 
Inspect all wires for worn or broken insulation that that could be rubbing against the engine block or in the throttle control box. You have a short somewhere that could be blowing the fuse. Good luck
 
This could be a bear to find ...first i would ask him if he has done any changes to the wiring at all..added anything to the boat?replaced any part that could be remotely related..is the problem solid or intermittent?does it blow every time he run and then stops the engine?when is the fuse blowing?is it blown when he stops or is it blowing on startup?are the fuses he is using the correct ones?some fuses are quick blow and some are delay...the slow blow or delay will carry some additional current for a short period of time before blowing..i would try to get the motor to fail at home running off muffs....the first thing i would try to determine is exactly when the fuse is blowing...i would also run the motor with muffs at night with complete darkness and see if you can see any fire jumping in the block area..i would simplify the wiring as much as possible..take everything off the battery but the big cable going to the motor..there is one thing i am not sure of but i think the motor if already started will run with this fuse blown...in other words it will be blown when you stop the engine but you will never start it with the key...i had a evinrude 90 that this was the case once..if the problem is solid i would also disconnect the wire from the regulator to the battery..you can start that engine all day with a fully charged battery without it being charged while running...
before you get into any serious troubleshooting i would take my time and give the wiring on the motor a good eye balling...separate wires etc and look for insulation gone or wrinkled where it has been hot..look real close where the wiring touches the metal...fix any corrosion you see in the wiring regardless of where its at...its future trouble anyway so fix it..
 
as Will said the problem could also be in the throttle control box or the key area...eyeball that also...if the problem is solid start the engine and then kill it without putting it in gear and see if the fuse is blowing without moving the throttle..that could further isolate the problem...it does not eliminate the key switch but it could either point to a chafing problem etc when moving the shift lever or not..the fuse could also be blowing when operating the power trim is something to keep in mind..
 
the wires don't appear to be broken I'll check at night for spark this boat was recently bought and I don't know if its previous owner had any problems, you'll gave me a good starting point some of the wires looks smashed thou we did have a problem with the power trim that could be a contributor thanks
 
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FishingLane said:
Hello j trax, I am having the same problem with my 115 hp Johnson. How did the problem get resolved? Thanks
Click to expand...

If you are blowing fuses, the first troubleshooting step is to figure out whether it is blowing right away or at some later time.
Do you know how to use a multimeter?

The fuse on the engine provides battery voltage to the ignition switch. The ignition switch, in turn, uses this to trigger the starter,
electrical choke (if equipped) and to power any accessories that may be connected to the ignition switch.
 
James, thank you for the info. I do know how to use a multimeter. I watched a youtube video on how to troubleshoot a short with it. I have the wiring diagram also. I have an Alloson circuit short/open tracer on order. I will work on this problem Thursday. I will post the results. Thanks, again.
 
The short was intermittent until I reinstalled the motor housing. Squeezing or bolting it tight caused the 20 amp fuse on engine block to blow. I was able to isolate the short to the power wire running from motor to ignition switch by disconnecting all of the trim circuit connectors and reconnecting them one at a time until the fuse blew. Verified short with ohm meter. Found insulation on two wires to worn off due to wiring rubbing between motor housing and a pivoting post with a carter pin. Spliced both wires and everything is good!!!
Thank you for your help.
 
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