2018 Honda BF150 ignition fuse blown

Just bought this boat brand new. Never even had it in the water yet. I was moving it in my yard today, went to trim the motor up, it moved for a split second and then blew the #3 10 amp fuse.

The boat has an extra trim switch at the bow near the trolling motor. It’s been raining every day for like a month and the cover is not perfectly sealed there so I’m thinking maybe some water got into or behind that switch and blew the fuse? Isolated incident? Bad luck?

Is there something else I can look at? Everything seems to work fine after changing the fuse but I really don’t want it to happen again. I also don’t want to hand this thing back to the dealer and lose weeks of my season.

Any exposed switch on a boat should be sealed from water so not likely it’s that switch at the bow. Unless that’s a bad new switch? It could have been a bad fuse? Keep using the trim and see if that fuse blows again?

And carry a few extra fuses on the boat just in case.

Thanks for the inputs. Went a couple days with no issues but today I’ve blown it three times. Definitely something wrong. I blew two from the bow trim switch, so I unplugged it, and then blew one from the main control trim switch with that bow switch unplugged. So all in, I’ve blown a fuse at all three positions, bow, control and switch on the motor. All on the “up” motion if I recall. I have no idea where to look now.

Also took the control box out, inspected, disconnected and reconnected the green, blue and white trim wires. Traced everything as far back to the engine as I could. Inspected the wires at the main harness and at the trim motor. Everything looks completely normal.

So have you used the switch on the outboard itself, does it blow a fuse? Must be a dead short somewhere.

Yeah, the first time it blew was when I was trimming it up from the motor mounted switch to move the trailer. Subsequently it has blown from both of the other switches at least once. I may try to disassemble the side mount control box and check the wires in the handle.

What I am not sure of is, since it blew once using the engine mounted trim switch, does that also energize the wires going up through the control handle, thus causing the short in there? Or are they completely isolated from one another. If they aren’t connected I guess it would be a waste of time to look at the controls if that makes sense.

Just thinking out loud now...I know the bow mounted trim switch is piggy-backed from the control box trim wires and connected with bullet connectors.

I can get back there and unhook the wiring at the control box that leads up to the bow mount switch. That would eliminate any shorts in the wiring up to there on top of the switch up that that I already ruled out. Further, I can disconnect the 3 pin connector at the control and eliminate the control.

The difficult part is duplicating the issue or trying to. It happened 3 times today, twice one right after another like clock work. But it was fine for days before then. And then today I did the things I noted in my prior post, and it’s been fine. Neighbors must think I’m crazy trimming my motor up and down all the time.

This is a process I use on finding a short in my old antique cars, maybe you can adapt it to what you are doing. The beauty of it is that it will allow you to find a short once you have blown a fuse once, you don't have to keep repeating blowing fuses. Plug all your switches in before starting, then keep trimming until a fuse blows.

Get a 12v bulb and socket (I've used the bulb and socket from a brake/signal light, the bulb is dual filament) - Wire some pigtails to it and clip it across the BLOWING FUSE (cover any exposed metal on the socket with tape). One lead to one side of the blown fuse, the other lead to the opposite side. If the fuse is blown due to a short - the lamp will light. The resistance in the lamp filament will prevent any damage to the circuit. ie SMOKE. The bulb will light AS LONG AS the short is there, leave it connected and lit as you do the next instructions.
Unplug the various suspect wiring connections - if the test lamp is still lit - the problem hasn't been found yet. Keep going until you disconnect something and the light bulb goes out, you found your short. Use a long wire on the pigtails so you can put the bulb and socket up high enough so you can see it from wherever you are working.

http://www.impalas.com/1961-67-chevy-tail-turn-signal-socket-oem-type-plastic.html

Something like this is what I used, I've not tried it with an LED, you may be able to pick up something from an auto parts store for a utility trailer. I had some old car wire harnesses that I could cut up.

Most common place for a short in the trim circuit is in the throttle/shift handle itself, to inspect , remove handle completely and dismantle it include the neutral lock and look for damaged wires

Also, one other place to look is where the wire to the trim motor comes through the cowling. There should be an insulating grommet there which is supposed to protect the wires from chaffing, but they sometimes get damaged. See #10 at:

https://www.boats.net/catalog/honda...p/bf225ak3-xca-2007-and-later/power-trim-tilt

Also, inspect the plug where the harness plugs into the trim motor wiring.