Hello,
I have a '93 90hp Johnson on my Stratos 260. Over the past few trips I find that my trim works intermittently while running on the water. I have inspected the relay box/wiring, tested the relays according to my seloc manual, replaced relays just to make sure, inspected all 3 of the trim switches (motor housing, control and bow). Inspected visible wiring with it all looking good. Has anyone ever dealt with this kind of issue? One main problem is that it the "short" or whatever the problem is tends to correct itself before I can accurately find it. The last time I thought I would get a good chance to find it, I had to use the manual pressure relief screw to put it up on the transom saver. By the time it got home it was working again. Does anyone know what I can try? I've thought of replacing the entire wiring harness but if there is another option that you know please share. Thank you!
Justin

If the problem moves with all switches, it is a connection to the trim motor from the relay box or the trim motor itself. Try to check if its getting voltage to the trim motor. Or next time it does`nt work, tap the top of the trim motor. If it starts working, you will know thats it.

Thanks Gary Purdy,
In the process of checking wires I had tested voltage on the blue and green wires before and after the 2 pole plug to the motor. It showed a problem with the plug connection. I found it to be corroded and I did remove the plug from the wires and connected them direct by soldering and using shrink tubing to insulate. The problem has continued since then. I did get the motor inspected by an electric motor shop. I inspected it with them and all it needed was to be cleaned it up and did minor maintenance as they said it was in good working order to begin with (you can't take one in and not expect to get charged for something). Today I'll mess with it and see if knocking on it will do the trick. If not I'll see where to go from there. Thanks for the input! I'll sure give it a try. This has been a real aggravating problem because I can't readily get it to fail or reliably get it located. Thanks again!

check all push on plugs at switches and relays, if any are even a little loose then pinch them with some pliers. since it is when running or trailering it sounds like you have a bad connection somewhere. look for any wire with black burn marks at the terminal, this would be from heating up due to bad connection.
get someone to help you and use a multi meter at the relays, one at a time have someone activate the switches and check for voltage before the relay, this should tell you if a switch has gone bad, low voltage.

Thanks for all the help so far. I did get a chance to run the boat this weekend. The trim will not work only when the boat is in gear and running. Any other combination the trim works. (engine running in neutral, not running in gear, etc.) Truly a stumper for me. I checked all plug connections. I have a parts motor so I've swapped out the relay plugs/wiring. Everything tests right. I'm looking for an area to use as a test tank as the docks at the lake are public state park docks and have a 10 minute limit. Even so, I can't figure what would change just from being in gear and running vs just having the ignition on and putting it in gear. If this opens any new thoughts or ideas up let me know. The motor also started to lack power on the way back to the dock, wot with the current prop is about 4800, it dropped to a max out of 3800. Hopefully unrelated, ultimately another post though.
Thanks for the help so far, any future help is appreciated.
Justin