Adjusting BIII trim indicators?

[DavidS]

A mechanic (dealer) misdiagnosed my position switches on BIII's and replaced the set. When he tried them after the repair and the gauge still didn't work he said "Ah, you are gonna need a gauge too". Rather than wait on another service call etc... I replaced the gauge for $37. Sure enough the gauge came to life. It would show the drive coming up but would do nothing going down. After one or two tries it is now (the gauge) stuck at about half way up with no response. I am assuming he replaced the indicators but was unable to sync them with the gauge since it wasn't working. Does anyone know how to do this? There is one adjustable switch on either side of the drive.

Thanks...

 

[H2ONUT]

This should help ya...

http://www.sterndrives.com/replacing_trim_senders.html

 

[DavidS]

Thanks for the reply. I see where it talks about the symptoms etc... but not how to actually adjust them.

It looks rather straight forward. There are two set screws in each unit, loosening them allows you to rotate them on the housing. When I rotated the starboard I could adjust it to "o" trim gauge with the drive all the way down. When I lifted the drive the gauge would come up. When I lower the drive the gauge stayed stuck in the up position even though the drive is down. I wonder if the new sender is bad, or is there another step to adjust it?

 

[H2ONUT]

Sorry bout that... I thought it was in there... :smt021

I have only done the sender on a Volvo drive. I need to do mine this spring on the Alpha.

I'm still searching for info. :smt017

 

[MLauman]

Sounds like you are on the right track. Try this one: http://www.mercstuff.com/trim_limit.htm

 

[Dave M.]

You don't say in your post what the mechanic did when he replaced the senders. The kit comes with replacement wires, as Merc says they are rhe most likely thing to fail. So did the mechanic replace both the senders and the wires?

The kit comes with two small ceramic 'circuit boards' that help provide the indication. They are not the same, and things will not work properly if they are installed on the wrong sides. I think they physically fit in the wrong places, so could be installed wrong. But if your trim gauge ever worked where you could get a part scale indication after replacement, then they are not wrong.

The sender that is the limit switch, and I think this in on the port side, is just a contact that is open or close. It consists of a round ceramic board with conductive material deposited on it. Fingers in the housing wipe along the surface of the ceramic as outdrive rotates, and either make contact through the conductive portion or don't.

The trim indicator on the starboard side is a ceramic board with a deposited resistor on the surface of the ceramic. Fingers slide along the resistor, and this provides a variable resistance of between zero and about 180 ohms to the gauge. As I see it, there are six things that can go wrong here.

1. The gauge can be bad.

2. The wires to the sender can be open or shorted together. I think open would be the normal failure mode, and would cause the gauge to read full 'up'.

3. The fingers can be bad due to water intrusion as described in one of the links above. I think this would also cause a full 'up' indication normally, but often the guage will be intermittent first.

4. The circuit board with the resistive film can be bad. This happened to me. What can happen is that one end of the resistive material fails to contact the metalic deposition, so you get an open resistor. Result is flaky, intermittent readings. then maybe full up again when it fails totally.

5. Not sure how this can happen, but the circuit board rotates in the housing, and is rotated by being keyed into the fixed part of the outdrive. The circuit board has a plastic extension on the back that slides into the keyed hole in the outdrive. If the keying stripped for some reason, then the resistor would not rotate. So it could end up with an non-moving incorrect position indication.

6. The two sending pieces could be swapped if replaced incorrectly. If it ever worked properly after replacement, this is not your problem.

This thread belongs in the electrical section.

 

[DavidS]

Thanks for the replies. Good info...

Dave M- I wasn't there when the mechanic replaced them so I don't know if he re-wired them or not. Seeing how it would be easier to replace them without re-wiring them, I would guess that he did not.

M Lauman- Thanks, that's what I tried but they only made one trip up before the gauge stuck at 1/2 way. I'm betting I have a bad indicator.

 

[DavidS]

It turned out to be a bad (new) part.
Thanks for the replies...