motor trims up automatically when throttle is increased.

[rachiebre]

we have a 21' pontoon boat with a 90hp yamaha motor. when we increase the throttle to a little more than halfway (sorry, i don't know the technicalities), the motor tilts up to almost out of the water. when we slow down we can put it back down, but when we speed up it comes back up. We were told it needed hydraulic fluid? if so, where do i put it? (its kind of embarrassing that i have to ask!)

 

[99yam40]

Re: motor trims up automatically when throttle is increased.

Sounds like the trim/tilt motor would have to be turning on to tilt the motor up as you are saying during power up, not a low oil level.

 

[rodbolt]

Re: motor trims up automatically when throttle is increased.

its an electrical problem not a hydraulic one.
unplug the pan switch and retest,if it still does it unplug the control box switch and retest.

 

[mcanderson1]

Re: motor trims up automatically when throttle is increased.

possibly wires for trim switch in control are frayed and making unwanted contact.