I have a 2003 Mercruiser 350 that was running fine on the land but after we took it out for a run last weekend it will no longer idle. I believe the issue is bad gas as there was about 20 gallons of old fuel that sat in the tank for 2 years. I should have pumped it out and cleaned the tank but instead just added fresh gas. Sometimes I can get it to idle but I found that I can recreate the symptoms by revving the engine to 2500-3000 rpm and then bring it back to idle. Once I do that then the engine starts to run rough and then any little bit of throttle will cause it to stall. I plan on rebuilding the carburetor this week once I receive the kit but wanted to get everyone's opinion if something clogged up the idle jets and would be causing the issue. Thank you!
I did that and the gas definitely didn't look good. I replaced the fuel/water separator and then tried running the boat off a portable tank. It had the same symptoms so I am thinking the damage was already done to the carb.
I recently bought a used motor to replace my original 1997 one and found out that the motor had a bravo ICM on it instead of the Alpha one I need. Do you think that that control module might not be advancing the timing correctly and causing it run rough after increasing the rpm to 2500-3000 and back down. I found a bunch of ICMs on Amazon but I can't tell if they are for the Alpha drive. My problem was that the shift interrupter wasn't working with the Bravo ICM.
I will have to search my house for the old one as I removed it 2 years ago but I was able to get the shift interpret working by taping into the green/white wire on the sensor under the distributor and connecting it to the shift interrupter switch. That allowed the interrupt to work but then I ran into this problem.
Engine Dies at idle
Linear Mode
