TM: risk of fried electronics?

While transferring my 1197 transducer from an old 80# Terrova to a replacement unit, I stumbled across a design deficiency with the potential to short the leadwires from the control head to the motor. Sorry I didn't get a picture while the old unit was dissembled--but here's the relevant parts on the Terrova parts diagram.

NOTE: other models and brands of motors may also have this problem.
http://i267.photobucket.com/albums/i...va_diagram.gif

The lower half of the control head (255) is attached to the composite shaft (200) with a machine screw (260) and nut (270). The leadwires (135 & 136) feed down the tube alongside the screw and may be in contact with the screw--there isn't a lot of space in there. Unfortunately, the screw is threaded from end to end--allowing the threads to chew into the insulation of the leadwires as the motor vibrates (when running) and bounces (on the highway.)

After 188 trips, that's exactly what had happened to mine. The insulation was eaten away & the screw was in contact with bare copper wire. Fortunately only one wire was damaged--if the steel screw chews through the insulation of both wires the power will short--possibly damaging the motor's electronics, and certainly causing a trip to the repair shop. Since the damage happens very slowly, it most likely won't surface until your motor is long out of warranty.

There are several ways to avoid this problem, the simplest being to replace the screw with one that is only partially threaded.

Check your motor now & avoid an expensive repair later.

I was just repairing a transom mount MinnKota, and noticed the same thing, screw threaded to whole length. Not really sure how there would be much wear on the wires though, except maybe vibration. The control board and shaft are fixed together, so the wires wouldn't be pulling during operation. Unless it's your transducer wire that's causing movement of the motor leads.

The cable for the 1197 is on the outside of the shaft, not inside. The only other wires inside the shaft are the ones for the unused US2, and there's no play in any of the wires running through the shaft. This problem appears to be entirely due to the vibration caused by roughly 2,000 hours of operation plus 400 highway hours.

What would have happened if both power leads had worn through and shorted? These wires are between the maximizer and motor. Would this kind of problem fry the maximizer or does it have its own breaker to prevent damage on the outbound side?

Richard, call MK about this problem. I'm sure they would want to know.

Thanks for the info.

Thanks for the heads up on this. Think I'll put a piece of tubing over the bolt. Don't think the circuit breaker at the battery would help much in this instance.

Sent from my MB860 using Tapatalk 2

Thanks for the heads-up. Think I'll put a piece of tubing over the screw.

Sent from my MB860 using Tapatalk 2

Quote:

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Originally Posted by Corker

The cable for the 1197 is on the outside of the shaft, not inside. The only other wires inside the shaft are the ones for the unused US2, and there's no play in any of the wires running through the shaft. This problem appears to be entirely due to the vibration caused by roughly 2,000 hours of operation plus 400 highway hours.

What would have happened if both power leads had worn through and shorted? These wires are between the maximizer and motor. Would this kind of problem fry the maximizer or does it have its own breaker to prevent damage on the outbound side?

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There Ya go, you just fish too much! LOL! It really isn't too smart of a design. I imagine the control board would be fried if they shorted. Not sure why they didn't use a screw with just threads on the end where needed.