BF90 keeps blowing 15 amp fuse

I am working on my 2005 BF90. I have another working BF90 on my other boat of reference and a service manual. My 2005 was a sinker but I am almost finished with replacing everything. I have put on a new power tilt and trim relay, ecu, coil packs, wiring harness, rectifier, starter relay, new tiller handle with associated wiring, new battery cable. The problem is this: the 15 amp fuse blows as soon as I put it in its place! The motor side trim button works even after the fuse blows. The tiller tilt and trim doesn't seem to be working. The fuse blows even with the key switch all the way off.

What causes current to run through the 15 amp fuse even when the motor key swith is turned off?

Sobie2

Most likely you have a short between the engine 14 pin connector and the tiller arm.

Before you blow any more fuses....connect a test light in place of the fuse. The light should come one.

Leave the test light connected, then disconnect the 14 pin connector from the tiller arm. If the light goes out, the short is in the tiller arm, if it does not, then the short is in the engine harness.

Your trim and tilt on the motor still works because it picks up its voltage on the hot side of the fuse.

The fuse feeds the black white lead to the tiller arm....key switch, trim/tilt, and alarm.

Once you know which direction to look, then just follow the black/white lead and disconnect wires along the way. When the light goes out, you are getting closer.

Look closely for the black/white connected directly to a black lead along the way. It is an easy mistake to make.

Mike

Thanks Mike,

I bought a test light (soldering iron looking pick type) $5 at NAPA. I undid the tiller arm, no change, then using the wiring diagram in the service manual, I undid the power tilt engine swithc, no change. Then I undid the rectifier, and the light went out. I have a new rectifier in there (and the old one, and they are both sealed electronics), so the problem is upstream of the rectifier.

Unfortunately then I had to get back to work after my lunch break was up. So after work I will again tackle this issue. The wiring diagram says the rectifier goes to ground (a clean contact area now with all the work), 3 greens that go the the alternator via a triple plug connector at the to of the plug in switch bar (easy to test that connection), and a single white that says "coupler bracket" So I will test those and see where next things go.

At any rate thanks for the tracing technique. I will report back when I find the problem.

Sobie2

I think you are looking in the wrong direction. The voltage comes from the 30 amp circuit breaker through the rectifier to the 15 amp fuse holder. The rectifier is also using the same wire to feed 12v to the trim/tilt switch on the engine, which you said is working correctly.

I think the short to ground is somewhere between the fuse holder and the 14 pin connector. I have a feeling that if this motor went under water, the wiring harness may have acted like a wick and it wicked up water under the insulation and corrosion was formed or the harness got pinched somewhere. You will probably have to eventually cut the wrapping off of the wiring harness from the 14 pin connector to the fuse holder and your will probably find the problem. Give a real good visual check of the harness going to the 14 pin connector and look for anything unusual (ie: radical change in shape, color, etc).

Another way to assure which direction to go.....clip one end of your test light onto +12v at the battery or at the point where the battery cable attaches to the engine. Then touch the other side (ice pick) to each of the contacts on the fuse holder. When you touch the contact that lights the light, that is the side that is grounded. Follow that wire. As I said, you might have to unwrap the wiring harness until you find the problem.

Also, look real close at where the white/black lead connects to the 14 pin connector and look at the pins real close for corrosion.

Another way to prove to yourself that the ground is going toward the 14 pin connector is to leave the test light connected like I said and then stick your probe in the contact where the white/black lead connects on the 14 pin connector. It the light lights, then there is a ground there too.

Make sure that all your testing is done with the 14 pin connector disconnected from the tiller arm.

Mike

I am going in the wrong direction, last night I followed it all the way to the starter relay, and yep it was connected to the 30 amp fuse. I did replace the wiring harness though. I will try working the test light from the 14 pin connector. Darn I didn't take my manual to work today so I can't follow the diagram.

Till next update, thanks.

Sobie2

I know it is a little late, but if you need a wiring diagram at work, you can download one with the owner's manual from honda-marine.com. It is at the rear of the manual.

Mike

Ok again I went to look at the motor. For a moment I got the fuse to not blow and the power tilt and trim worked on the tiller, but no key switch operation. Then I went to plug in the neutral safety switch and choke solenoid and it blew, but maybe I bumped the 14 pin coupler in the process. The problem does appear to be in the tiller handle... but that darn thing is brand new! The coupler seems to be good, there is a sharp bend in the wiring. So I guess I will have to strip down that whole wiring harness, maybe when it was assembled the coverplate ended up pinching the wire.

Sobie2

Well it was a pinched wire in the tiller handle. Talk about annoying, that was a brand new tiller from Honda, and it came with a wire pinched by the cover plate. That caused the short. So now I should get some of that liquid wire covering to prevent corrosion. Thanks for your help Mike.

Sobie2

Glad you found it.

Mike