Boat is running rich 02' tige 350 mpi

[soccerboy007]

My boat is running rich, yo can smell is when you get to the exhaust. I had replaced the fuel filters last time and now the boat will not go past 25 mph. the boat seems to run fine but it does feel a little tired, thats when I noticed the smell. I am not sure what kind of sensors are used to deternime air to fuel ratio on this motor and also the vaccum hoses. If anyone has any idea what could cause the boat to run rich and what to check for please let me know. Thanks to everyone who helped me with the fuel delivery issue last time.

[R&T Babich]

My boat is running rich, yo can smell is when you get to the exhaust. I had replaced the fuel filters last time and now the boat will not go past 25 mph. the boat seems to run fine but it does feel a little tired, thats when I noticed the smell.

Make sure you didn't loosen a plug wire or two. Our boat had a cracked spark plug. It seemed to run fine and had plenty of power compared to our old 302 sterndrive. You could really smell the exhaust - unburned fuel. Replaced the plug and wow, even more power and no more smell. Check the plugs for ones that are all black and oily. If they're all black then you've got some sort of fuel control issue. Is the engine a Merc 5.7L Mag MPI?

[soccerboy007]

the motor is a mercruiser 350 mpi I'm not sure if its a mag

[Jason B]

Is it the fuel that sat in the tank all winter long?

[laserfish]

If it is old fuel, that can clog injectors, filters, and it stinks really bad when it burns.

[whitlock87]

I had this problem on my 04 with the same engine.
I turned that my ECM needed to be reprogrammed. (The battery died on my one day, so I had to jump start the boat. Doing this cause the ECM to lose its program. I have also herded that charging the battery with the master switch in the on position; can also cause the ECM to default back to the factory settings.)

[soccerboy007]

I have take all the fuel out and put new fuel in there. I dont know where the master switch is at so please give me some instructions of where its at.

[whitlock87]

I have take all the fuel out and put new fuel in there. I dont know where the master switch is at so please give me some instructions of where its at.

its in the back locker left side. it is the red switch that has on and off on it ( just twist)

[infotom]

pull off the vacuum line to the pressure regulator, see if the inside of the hose is wet or smells like fuel. if so, your regulator is bad pulling raw fuel into the intake. causing a rich condition.