Skeedeen | Monday, April 12, 2010

The only item not yet addressed on my work list was the trim tabs, which the owner reported did not seem to work.  Not knowing what to expect, I'd postponed this job till the other work was complete.

After some online research to locate manuals, schematics, and troubleshooting guides, I prepared to begin the task.  The first thing I noticed was that there was a switch on the DC panel for "trim"; I turned this on, wondering if it could be that simple.

Perhaps it was, but it was a longer road to get there than it should have been. 

With the batteries turned on and the proper switches thrown, I tried the helm control for the tabs, and was rewarded with the sound of a motor (I thought).  The problem was, the sound came from the wrong place:  in the engine compartment.  The trim tab pump was located aft, in the bilge near the transom.  This was bizarre, and my first thought was that somehow the trim tab control had been mistakenly wired into an unneeded trim pump on the engine, since this engine was one commonly used with stern drives, which feature a trim pump to control the attitude of the leg.

Tracing the wires, I found there was no way this could be, and it'd been an odd long shot anyway that would have made no sense had it been the case.

Next, I inspected all the connections, traced the power supply back to its source, added hydraulic fluid (ATF) to the pump reservoir, and several other tasks, to no avail.   Wondering if an add-on box (which I thought was an auto-tab retractor) was malfunctioning, I disconnected it from the wiring circuit and plugged the wiring harness directly into the trim tab pump.  Nothing.

Adding to my increasing confusion, I discovered that when the engine key was turned on, the trim tab control stopped causing the motor noise I'd heard before.  However, this also provided a critical clue:  the key activated the same sound.  Fuel pump.

Why would the trim tab control operate the engine's fuel pump?  Checking other switches, I discovered that just about everything I touched operated the fuel pump, or else did nothing at all.  This should not have been, obviously.

Next, I disconnected the power supply to the trim tab control, and wired it directly to a battery, bypassing everything else.  The control still made the fuel pump run when any of the buttons were depressed.  Now, I could just not determine any reason how this could possibly be so, which was rather frustrating.  I started suspecting a grounding issue, something buried deep within the boat somewhere that I'd never find...

...but this led me to the solution.  Something clicked--albeit slowly--in my mind.  Last Friday, following the installation of the new aluminum deck hatch over the battery compartment, I'd reinstalled the batteries, which I'd removed during the installation.  All the morning's weirdness had finally caused me to have a dim memory:  had I reconnected the small negative wire that ran to the ship's negative distribution busses?

I had not.  During the various projects, this wire had dropped into the bilge behind the platform, where the exposed section looked just like a transducer cable--same color, same diameter.  So I'd missed it for whatever reason.  I reconnected this wire, after which everything worked as it should--including the trim tabs, which I ran through a full cycle and visually confirmed.  There was a two-hour stretch I'd never get back.  Fortunately, I don't charge for my own foolishness.

With that project out of the way, my work list became virtually nonexistent:  just some additional varnish work, with another coat required on portions of the windshield and helm area, and two or three additional coats required on the new forward hatch frame before I could complete the hatch (and some trim) installation itself.

After working on another shop project or two during the afternoon, I reinstalled the cockpit trim pieces that I'd removed for varnish, and applied more varnish to the other areas as needed, likely wrapping up the bulk of the varnish maintenance this time around.


Total Time Billed on This Job Today:  4 hours (not including "diagnosis" time)

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