blown 20amp fuse

[zachmeredith]

I took a weekend trip to my favorite lake and after running my motor for most of the morning I blew my 20amp fuse in my 02 Merc 150 opti. The last run was a 4/5 mile run and while on plan, I blew the 20amp fuse in my motor killing my motor and trim. I pulled the cowling off and replaced the fuse and the fuse immanently popped. I was towed back to the marina (took about 2hrs to get back). After putting my boat back on the trailer I attempted to replace the 20amp fuse and it worked with no issues. the next morning I made another run and about two miles pop goes the fuse and my motor and trim are out. I pulled the cowling off and felt around for warm or hot wiring and couldn't locate any. I trolling motored around for about an hour and was able to replace the fuse and make my run back to the marina with no issue.

Before the trip I replaced my Cranking batter with an Optima group 31.

I'm guessing because the issue is my key ignition switch, battery or power cables from battery to motor..

any help would be appreciated.
Serial Number OT486088
2002 150L OPTI

Thanks,
Z

[EuropeanAM]

Problem is likely in the engine keyswitch wiring, or the control.

Which type of control do you have (and where is the keyswitch located)? Have a picture of these?

[zachmeredith]

[zachmeredith]

I believe I have a key and horn assembly with no push to choke. The key switch is located on my left side of the dash.

[EuropeanAM]

Common locations for shorts are:

-Where wiring exits cowling or splashwell
-Along gunnel (rub-rail screws rubbing harness)
-Around steering components at console
-Trim wiring in control handle
-Trim wiring at bow switch

[zachmeredith]

Awesome thanks for the help! Anything in particular on the wiring I should be looking for to determine the short?

[EuropeanAM]

Bare or chafing red, purple, blue w/white stripe, green w/white stripe, yellow w/red stripe wires (any of these colors).

[tomloans]

Mine recently did the same thing and it was a bad coil. Look at your cools to see which one is cracked and sometime white foam will protrude from the crack.