Hello, I have a problem, well actually several problems with my 2003 Mercury 90hp OT 605708. I would start it and it would not stay on. Or it would idle for a min and it would turn off. Someone decided that the carbs would need to be cleaned. I took it in to the shop and had all 3 carbs taken out and cleaned. Once they were placed back the shop turned it on and this time the motor stayed on. They even punched it several times and the engine responded. It would die if I tried this before the carbs got cleaned.
I filled up my portable fuel tank with new fuel and I took the boat to the lake a couple of days later and it started right up at the ramp. While I was moving real slowly waiting on my friend to park the trailer the motor cut off. I cranked it right and it would not start. I had to anchor on the spot to keep from floating away. After trying for 15 minutes, it finally turned on. I picked up my buddy and started out. I traveled about 300 yards and decided to stop and anchor. After about 30 minutes, we decided to move again and the boat would not start. So for the next hour we sat there trying to start it up again. The primer bulb was firm. The fuel was new and in a portable tank. Finally got to the dock and got out. That evening while in my driveway I tried to turn it up to flush the motor and it fired right up. The next day in the morning I tried it again and once again it turned right up. I decided to check compression and the readings were 112, 115, and 115. But here is where it gets strange.
When I finished the compression test and placed the plugs back in I decided to turn it on. It turned on right away, I decided to trim the motor up a little (away from the transom) and the motor died. I trimmed it back in and I cranked it and started right away. I trimmed out again and it died again. It got to a point that I would trim out and it would start to putter and about to turn off and I would trim back in and it would sound normal again here are some things that some people have said:
1. The vent is defective on the portable fuel tank thus creating a vacuum lock
2. The floats on the carbs are stuck or need adjustments
3. The grounds wire need to be tightened
4. The fuel line gets kinked thus cutting fuel to the motor.
5. The fuel pump needs to be replaced or serviced.
Please tell me someone has encounter or heard of this problem before. Thanks for your time and sorry about the long post. I just wanted to get the majority of the information out there. Thank You.
Pete

While I waa reading your post I was thinking fuel tank vent the whole time. I'm not a mercury expert and bet.you get.some better advise soon though.

How far up do you have it tilted?

I have an uncle that traveled with his motor in the tilted up position all the time and when he backed it into the water the angle of the ramp would make the motor look like it was trimmed down a lot more than it was. It gave him fits to get started until he figured out he had it tilted too much.

Sounds like you might have a broken wire in you wiring harness. Without trimming your motor up wiggle the remote wiring harness by hand and see if it shuts off. If it does try to locate where your short is. Also check inside the cowling where the harness plugs into the motor harness and make sure it is not too short possibly pulling it apart and disconnecting itself.

Thank Tommy. I will look into your advise.

Pete