Conference vicki::boats

I hope your boat is on the trailer.

Tilt your engine all the way up. look on the aft side of the transom clamp,
on the left hand side, inside. You should see a black plastic block with a 
movable arm that pivots. That arm follows the moving part of the outboard,
and while it's moving it is also moving a variable resistor. This is how your
trim gauge works. That arm sometimes gets stuck - weeds, salt, general guck.
Spray the heck out of it with WD-40 or CRC-66, and "work" the movable arm 
until it frees up. This works for me.

                +----------+ <-Transom clamp, looking from astern of 
		|X         |   your boat toward the outside of the
                |          |   transom.
                |          |
                |          |
                  X-marks the spot where the trim & tilt "sender" is.

    
     I'll give it a shot and let you know.....
    
    
                                       Thanks....

    
    
      Well... That's not it...Does anyone know how to test the
    sending unit back by the motor ?
    
    
                                          Thanks
    
                                                 Tom
    

    First check for + 12 volts on The I trminal on the back of the guage
    when the key is on . Next check if you have a ground on the ground
    terminal on the back of the guage. Next with the key on connect a
    jumper from the s terminal on the back of the guage to ground. if you
    get a fuul scale deflecton on the guage , then the probel is either in
    the sender or the wiring to it. If the guage does not move either iit
    is bad or its wiring or supply voltage is not there. To test sender
    wiring ground both sender wires at the sender or connection block guage
    should deflect if it does not senderwiring is bad. To check sender
    disconnect both leads and put an ohm meter across it set to low scale
    if meter does not vary while moving sender arm  sender is probably bad.
    
        BIll
    

Moved by moderator...

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Note 764.0                   Mercruiser Trim Problem                  No replies
GENRAL::CBROWN                                       13 lines  18-OCT-1990 15:43
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    The last time I had my boat out the trim gage stopped working. I
    have found that the dual wires going to the sensors on the lower
    unit are both pinched off. The boat is a 190 Sea Ray with a 260 hp
    Mercruiser. There is plenty of slack on wire on the inside the 
    transom so I'm wondering if it is possible to pull the wires through
    so I can re-connect them. Has any body else had this problem and if
    so what did you do to stop it from happening again.
    
    	Thanks for any info up-front
    
    	Craig
    

    My trim gauge was fine last year, but has somehow gone partially South
    over the Winter.  (115 Johnson, 1990, similar motor to the base note).
    
    It follows the motor down slowly as it should, but when you get to the
    part of the travel where the motor moves very slowly (the range you
    normally adjust while underway), the gauge dives to the bottom.  
    Judging from the earlier replies I'd say it was a sending unit problem,
    but what problem would cause it to behave non-linearly with the engine
    travel?  Doesn't seem like crud would explain it, it's very repeatable
    (and very smooth, not like the circuit goes open suddenly).
    

    Jim,
    
    One good reply deserves another (Sailing re loran)
    
    > What problem would cause it it behave non-linearly.
    
    I think you have correctly surmised the problem. On open circuit
    in the sender would give exactly that symptom. Once the slider passes
    the open spot, instead of seeing some voltage (proportional to
    position) through a resistance, it would see 0 volts (ground) through 
    some resistance. It doesn't matter what the resistance at that point
    it is still 0 volts, since you are disconnected from what used to
    be a resistive voltage divider.
    
    Bill
    
    

    If it dives for the bottom smoothly, that's probably due to damping in
    the gauge circuit - like gas guages normally have.
    
    Bill
    

    
    
    	if i remember correctly the johnsons had a plastic 
    screw out plug in the port ram, behind this is a spring and a ball 
    bearing that runs up and down on the variable resistor inside .
    id replace this after checking that the wire from the unit was ok and
    not getting an open cct in a particular position.
    i had heaps of trouble with this in my 135 johnson.
    in the end i even had extra earths because of some mods id made.
    
    the other option is to put in a manual trim and disregard the electric
    
    this is the option i took with my merc as their senders are really 
    inacurate.
    
    the other reg
    

    My trim gauge sending unit was definitely open.  Went and bought a new
    one (@#$#%$$ $52 for a variable resistor, a spring and a couple feet
    of cable &$#^$^*).   
    
    The guy at Russo's said replacing it was a piece of cake.  The mounting
    of the sending unit looks simple - couple of bolts and good access with
    the engine tilted up all the way (doesn't even look like I'd need to
    take the boat out of the water).
    
    Of course nothing is ever simple - the wires from this unit join two
    bigger wires which must be the juice for the tilt cylinders themselves,
    and then they go into a black sleeve which runs through the transom
    forward under the motor, joins the gas/oil hoses (via plastic cable
    ties), goes into the motor housing near the front of the motor, and
    then snakes along the bottom of the powerhead and up the back of the
    block where they emerge from the sleeve and join some connectors.
    
    Removing the whole sleeve assembly looks pretty contorted.  There is
    very little clearance between the bottom of the powerhead and the
    housing, and a fair number of ties and clamps.   Has anyone done this?  
    I was thinking maybe I should connect some string or another wire to
    the loose end of the cable and pull it out of the sleeve at the sending
    unit end.  Then I'd have a fishwire to pull the new cable back through,
    althought I'd have to at least cut the cable ties and loosen up any
    other clamps.
    
    I could also cut the wires right at the sending unit and splice the new
    unit into the old wires, but I'm not thrilled about doing this in a
    location about 2" above the (salt) waterline.