1998 3cyl Johnson 25hp - Burnt wire in tilt/trim assembly

The powertilt/trim on my 1998 Johnson 25hp (3 cyl) outboard stopped going up. I boughtnew solenoids and that didn’t help. I found a burnt wire in the assembly andwhen I touched the burnt ends together it would go up normally.
So I soldered the wires back together and the tilt/trim worked fine...in thedriveway.
First time out on the lake, with the motor running, I hit the up trim buttonand it didn’t work.
With the motor running I took the cover off and found the wire was burnt again.I touch the wires back together and hit the up trim button and the wires got sohot it melted the solder.
When the motor is not running, and touching the wires together, it works.
When the motor is running the wires get so hot it burns right through thesolder.



I ordered a whole new assembly from:
http://www.marineengine.com/newparts...Engine=&Model=

The new part came in and installed easily. Same thing again, it worked fine inthe driveway but with the motor running it burnt right through the wire in thesame place instantly after touching the up button.
There went$75!
Has anyoneexperienced this before? Why would it work with the motor off but burnup with the motor running?
Any help or advice would be greatly appreciated.
Thank you.
Jim

is the power wiring for the trim from inside the cowl or has the trim been added and you have wires going to the battery?

when you say it works fine in the driveway and then burns up with the motor running....do you have it in water running or with muffs?

Thank you for responding.
The tilt/trim was factory installed equipment and the power wires connect on the side of the motor.
When running the motor I am on the lake, not using muffs.

ok...first i want to verify that we are talking the outboard motor is the one you are talking about when you say motor running..then a few questions...did that assembly you replaced include the relays?....are you in salt or fresh water?...when you pull the boat out of the water did you look to see if water is coming out of the motor?try operating the trim immediatedly when you get the boat on a trailer....even if it dont burn the wire feel the wire and see if its hot to the touch....get some muffs and see if you can get the failure running out of the water...the problem dont make sence unless you have water getting into something....the battery has a higher current source than the charging system.....i would also get an inline fuse to place in the wire that is burning...the relays will weld a point sooner or later if its hasnt already happened and then you will have two problems....the first thing i would do is run off the muffs(with a dry tilt system) and see what happens...do you have a multimeter and know how to use it.?please get back to us..interesting problem......

View attachment 3793thhis is a two wire system..it may not be exact for your motor...

i want to verify again about the basic wiring....is this a correct statement?....all the wiring including the power source is under the cowl with no wires going to the battery.....if the polarity is reversed then this problem would make sense....somewhat...no wiring was added and the problem just popped up with no activity to possibly cause it?

Thank you very much for taking an interest in this problem.
To answer your questions:
Yes, I am talking about the outboard motor running when the burning occurs.
Yes, the relay assembly came with new relays.
The boat was in fresh water.
When the boat is put back on the trailer there is no water leaking from the motor (other than the lower unit).
I do not have a multimeter or know how to use one, but several of my friends do.
The wiring appears to be similar to the diagram you provided. However, the trim gauge has never worked and the bow trim switch quit working a year ago.
All the wiring is inside the cowl, nothing direct to the battery.
The problem occured the first time I put the boat back on the lake after having a mechanic replace a broken shift cable. I spoke to the mechanic and he said replacing a shift cable would have nothing to do with the trim not working or the problem I am experiencing.
I wish I could put an inline fuse on the burnt wire. The burnt wire is red, about 1" long and jumps between the 2 relays on the underneath side of the assembly.
I have not tried anything with muffs. All tests of this problem have been either in the driveway/on the trailer or in the water/on the lake.

When I picked up the boat at the mechanic after replacing the shift cable, the trim worked fine, up and down. While on the water, I noticed the up trim would not work.
Down trim worked fine and continues to work fine even with the burnt wire.
The new assembly burnt in the same place while the outboard motor was running (the little 1" red "jumper" wire underneath the assembly).
With the outboard motor NOT running, I can touch the burnt ends of the wire back together and the up trim works.
With the outboard motor running, I touch the burnt ends back together, touch the up trim button and it gets instantly hot and sparks fly.

I am so frustrated with this situation.
Thanks again for taking an interest!

Is it possible that while replacing the shift cable, the trim wires running from the console to the motor got damaged, which in turn are causing the problem?

thats exactly where i would look.....the problem may be happening with just the key turned on and the motor not running?....if you feel uncomfortable tearing up the controls then take it back to the mechanic....it should be a no charge fix as he put the problem on the boat...i am surprised there is not a fuse that should blow under the cowl..but i dont have a complete wiring diagram for that motor...look at the wiring close and see if you have what appears to be an inline fuse under the cowl....probably on the port side of the engine...it may be jumpered out...also on any wiring coming directly off the battery...people do strange things in emergencies on the water and never seem to go back and correct them....

if you draw a blank with the mechanic and have to fix the problem yourself i think the next step will be to start disconnecting wiring and attempting to eliminate and get it down to where we are operating the trim with the basic wiring...by that i mean eliminating the wiring to the control arm and bow trim and stuff like that....it depends on your level of expertise with electrical circuitry....i would still get the muffs and try to duplicate the problem out of the water...it would be easier to work on......i am going to my boat today for a few days...i have a computer there but i dont know how much time i will have.....but i will check and get back to you....

it is my thinking now that being in the water has nothing to do with the problem...fresh water short or ground is not going to draw enough current to burn a wire like that.....

From what I have read here, it sounds like the trim motor is shorting out in the windings inside as that is the only place that could cause enough amp draw to burn the pos. batt. feed to the up relay. This would be for a 3 wire trim system as posted Papyson. If it were a two wire system, it would cause problems going both ways. Easiest way to test is to disconect the blue wire from the trim motor at the relay and see if the wire heats up where it is burned.
Wirth a try,
Oldman570

agree Oldman but the fact that he has to have the motor running dont make sence......he has to start disconnecting to isolate for sure....is it a 2 wire or 3 wire system?....i assumed 2 wire from looking at that harness picture...

Right on Papy , If the boat wrench replaced a cable on the control the trim wires are pinched in it or the trim switch will be the prolbem. Has to be powering up both relays as the key switch has to be turned on for the problem to happen. Jimmy; Best to take it to another mechanic and tell him the history of the cable replacement, or back to the one that did the cable replacement, and what it is doing if not electrical savy , and not have a wireing schmatic. Your trouble has to be there as you have replaced the relays an harness already.
Best of Luck,
Oldman570