Mercury 90hp bucket of problems...Any input greatly appriciated.

[psjr57]

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

 

[enginepower]

Well you can't just name your problem and you get a solution. You need to perform checks and have an understanding of how things work. Doing a compression test was a big help on eliminating engine integrity. Depending on how high you are trimming, yes, it's going to run bad. When you are in water, back of boat leans back and puts carbs at a different angle than sitting flat or on down slope in your drive way. You need to figure out what you are losing, spark or fuel. Bring a spray bottle of pre-mix and spray into carbs and see if that changes anything.

 

[Texasmark]

I think you have a kinked wire that is shorting out. A good possibility is the engine kill wire in the control box. I don't have my manual any longer but it is either the yellow/black stripe or black/yellow stripe. Look at the wire on your fuel enrichment valve and it is the opposite.

When you turn the control off the ignition switch grounds this wire which grounds your trigger circuits and kills the engine. If the switch is crudded up internally, the ground may still exist when going to the on position and as such will be intermittent....depending on where the crud is at that time. I don't think any of the other problems are the smoking gun. The fact that you tilted the engine and all probably had nothing to do with it. I think you need a new switch in your control.

Mark