Weird Electrical Short

[Sam]

My wife and I just got back from the store and were unloading groceries when she came in the kitchen and said "Something just came on in the garage." By the time I got there I heard an electric motor run for a few more seconds, then it quit. Looking around my boat on its trailer, I saw that the outboard motor had power-tilted itself all the way up and fortunately the prop didn't quite reach my garage workbench. The rubber motor tie-down strap wasn't broken but the metal hook was straightened out.

My boat Is a Tracker TX-17 and I swapped the original motor out for a 50 hp Suzuki 4-stroke a few years ago. There are three power-tilt controls - up and down buttons at the front of the boat, an up-down toggle switch on the throttle lever, and an up-down toggle switch on the side of the motor itself. Standing there scratching my head, I figured my wife's cat must have stepped on the front deck "up" button - but I didn't see the cat.

THEN - all by itself, it did it again. The tilt motor went on for about two seconds, trying to raise the already all-the-way-up motor, then turned off again. O.K., I can't put up with that. Imagine if it did that when I'm not around or in the middle of the night - dead battery, burned-out tilt motor, etc. What if that happened while trailering the boat? Not good.

I disconnected the main battery ground wire and I guess for now I'll leave it that way and re-connect it at the launch ramp. Any recurrences while fishing would be a major problem, though. I've got to fix this, and since the short is intermittent I don't even know where to start. Suggestions?

[mic]

Ghosts.

[fishinwrench]

Attach a digital volt/ohm meter on the BLUE harness wire, you'll notice that there is "some" voltage present (probably from 0.7 to something less than 12v)

Now go wiggle some switches and relays while keeping an eye on the meter..... When the voltage reading goes to zero (no voltage) you found the shorted switch (or relay).

If it turns out to be a relay be sure to replace BOTH of them, and not just the UP circuit side.

If none of this makes any sense to you.....Take it to a qualified O/B tech.

[bfishn]

Attach a digital volt/ohm meter on the BLUE harness wire, you'll notice that there is "some" voltage present (probably from 0.7 to something less than 12v)

Now go wiggle some switches and relays while keeping an eye on the meter..... When the voltage reading goes to zero (no voltage) you found the shorted switch (or relay).

If it turns out to be a relay be sure to replace BOTH of them, and not just the UP circuit side.

If none of this makes any sense to you.....Take it to a qualified O/B tech.

'zactly. Prime suspect is the bow switch, then the helm, then the motor.

[Sam]

fishinwrench, bfishn, - thanks!

I think maybe I found and corrected the problem, but if not I'll take the boat to a qualified tech - 'cause you lost me at "relay".

Checked everything I could think of with a digital voltage meter and didn't find anything strange. BUT there's a plastic plate flush with the deck at the front of my boat and the motor-tilt "up" and "down" buttons and the three-point plug-in for my trolling motor are mounted in that plate. All three are threaded, pass through the plate, and are secured by flat nuts. The "up" button nut was 'way loose and that switch was flopping around and had a lot of wiggle in the hole, so I tightened it. Maybe being loose in the hole was causing something to ground out occasionally.

The wires to those switch buttons are real thin, and I'm thinking they must work like a starter solenoid on an old car - pressing the button just shorts out a small current to ground but that runs through a solenoid switch that sends current through a much bigger wire to the electric motor that raises or lowers the outboard motor. Is that right?

For now I've got the battery reconnected and my boat is on the trailer in the garage. I left the tie-down strap off the outboard motor and left it half-elevated. Made sure the prop won't hit anything in either full-up or full-down position, and I've leaned a small stick against the prop that will fall over if that motor moves when I'm not looking - high-tech, huh?

I'll disconnect the battery overnight for a couple of nights just to be sure, but I think the problem may have been that simple. The boat took a pounding running through whitecap waves last trip, so that would account for shaking some things loose. Thanks again!

[bfishn]

I doubt you solved your problem, as nothing grounds thru that mounting plate. If the switch was loose enough that the wires could contact other wires though, you're in business.

Your analogy to a car solenoid is on target. A relay does the same thing, using small wire/low current switching to close a set of contacts that carry the larger current, in this case directly from the battery to the trim motor. The DC trim motor reverses direction when the DC polarity is reversed. In this case, one relay provides normal polarity, the other reversed, to give up/down action. The relays are mounted on the powerhead.

If it happens again, the cheapest DIY first attempt is to replace the bow switch. Unlike the helm and motor switches, the bow switch is seldom suitable for wet applications, and the most common to fail. Assuming there's no stray voltage at the relay(s) coil as you suggest, it could take a (paid) tech a long time to duplicate the problem. Interrmittent electricals suck.

[Sam]

Interrmittent electricals suck.

Yep, and I'd guess a short would be harder to find in an aluminum boat. Anywhere a bare wire touches my boat hull or frame, hidden under the front deck or wherever, it would short out. Not so with fiberglass.

So far, so good, though - it hasn't happened again, yet. If this turns into a big deal I could do without those tilt controls up front. I didn't have a power tilt with the motor my boat came with. Power tilt came with the Suzuki 4-stroke I switched to about 4 years ago, and while I really like having it I usually forget I've got tilt control buttons up front. If I'm fishing along and get hung up on a stump, I'll be back to the driver's seat before I remember I could have raised the motor from up front.

[Wayne SW/MO]

There would likely have to be a relay involved because of the fact it tried to raise when it was already passed the limit. The problem, I would think has to be beyond the control buttons because the current from them should be in front of the limits. A short in or beyond the limit could do it. I.E., if the lower path was getting to the raise it would do the opposite because one should be energized all the time.