2003-75hp mercury power trim

[PDSNIPER]

Finished striper fishing at Lake Murray the other evening and headed back to my dock. Got the boat up on plane and noticed it wouldn't trim up so I shut back down to idle. I found that the trim motor was running in the down position. No trim switches were on (3) I finally had to take negitive battery cable off to see if it would reset the trim motor and it didn't. I did find that if I held the throttle trim switch in the up position the trim motor would quit running. I made it home holding the trim switch in up position. I took throttle trim switch apart in it looked brand new inside. I left the switch apart and connected the battery cable and the trim motor came on in the down trim. I then took apart/unplugged the trim switch up front near the trolling motor with the same results. I checked the trim switch on the outboard (didn't take it apart) checked all wires to the switch. I did find that if a took a small screw driver blade and crossed the up trim contacts the trim motor would stop running in the trim down mode. Could not get the trim motor to run in the up mode. Never had any problems or even a hint of a problem. Does anyone have any ideas??? Thanks Much

 

[gonefishin485]

Re: 2003-75hp mercury power trim

well, im not an expert, but to me, it sounds like your down relay is stuck in the on position

i know on an evinrude 115 i had, i had it rigged up with two 5 prong relays from the auto parts store, i dont know how a merc is setup, but thats what it sounds like it to me, if its possible, try swapping your relays and see what happens

im just thinking on the context of a power window motor, for example
driver holds button up to roll window up, smart *** passenger holds button down to finish their cigarette, window stays in the same spot untill one person lets go of their button

just a thought

 

[PDSNIPER]

Re: 2003-75hp mercury power trim

Thanks so much for your prompt reply. I have checked all the trim switches (2) and they seem to be fine. In fact when diassembled the trim motor comes on (down position) when I re-attached the negitive battery cable.

My next problem is I don't know where the power trim relay is on my system. I'm thinking it should be near or in the trim switch mounted in the motor cowl. Can anyone answer this for me. Thanks again for your help.

 

[Texasmark]

Re: 2003-75hp mercury power trim

I have the service manual for that engine in my lap. Trouble shooting procedures do not cover your problem. Soooooo

First, there are 3 relays on that engine: Start, trim UP and DOWN. You can find the start as it is connected to the starter. The others look just like it and are located somewhere under the cowl.

In the service manual they talk about the remote being inoperable and the cowl switch being operable, or both inoperable. Since the switches are in parallel, either could cause the problem. But I don't think that is your problem as indicated below.

The motor requires the operation of both relays. One or the other is the drive relay putting 12v into the blue or green wire of the trim motor. Whichever gets it determines the direction the motor runs and the trim movement direction. The blue or green wire not being fed 12v is looking for a ground which it gets through the relay not supplying the 12v. Energizing one or the other with the trim switch(s) determines which is energized supplying the 12v, and which is de-energized supplying the ground.

I think Mr. 485 nailed it. If DOWN is energized/stuck closed (on position) and the motor is turning because the green wire (wiring to the trim motor from the trim relay) has 12v on it, the circuit is completed through the ground (unenergized contact) of the UP relay and the piston retracts (DOWN). When you push the UP switch, the UP relay energizes and puts 12V on the blue wire and removes the ground from it. So, with both relays closed 12v is applied to both sides of the motor and the motor stops (12v on both sides) which is exactly what you have.

Replacing the DOWN relay makes sense to both of us.

My 2c

Mark

 

[PDSNIPER]

Re: 2003-75hp mercury power trim

Mark, thanks sooo much. Any ideas on how I can find the power trim relays on my motor? Would they be built inside the trim switch on the motor cowl or what would they even look like. Do you have any contacts and what would you do?? di

 

[Texasmark]

Re: 2003-75hp mercury power trim

Like I said, go to the hot terminal (red wire connection) on the starter and follow it back till you get to the start relay. The other two look just like it and are mounted somewhere under the cowl, either on the engine block, or a plate that mounts to the engine block. May be on a plate under a plate that is mounted to the engine block.

There are red and black wires on both, with green and green/white on one and blue and blue/white on the other. The wires with white are the control wires, the red and black are 12v in and ground. You know what the blue and green do.

If you still can't find them tell me and I will go out to my engine and see where mine are. Mine is 90- hp and is just a gassed up 75 so everything should be in the same place.

Let me know.

Mark

 

[PDSNIPER]

Re: 2003-75hp mercury power trim

Mark, I located the relays and found defective one. I replaced both of them and put everything back together. All is good and I can get back to striper fishing again. Could not have done it without your assistance. Thanks much

 

[Silvertip]

Re: 2003-75hp mercury power trim

Relays are plastic blocks about one inch square and two of them would be located next to each other on the side of the engine. They definitely are not built into the trim switch.

 

[rosser1]

Re: 2003-75hp mercury power trim

ypur trim has two relay the down is stuck open and they may be next to your tilt trim motor and resivoir. sorry not much help. change that and you will be good to go!