99 200 EFI performance issue

[careybirdwell]

My motors is a 99 Mercury 200 EFI Ser # 0G897614. The boat & motor is new to me and I never had a boat with an outboard motor on it, so I have a lot to learn. 1st off, it sat for a few years before I got it, I removed all old gas, and filter before trying to start. Once replaced, it started right up and ran good on the muffs, when I put it in the water, it would troll around at idle fine but when I would try to get the boat on plane, it was like the motor had no power (no rev in engine or rpm). It did this for about 10-15 minutes, then out of no where, it jumped up on plane and I was able to get my 20' Champion up to 58 mph om my GPS. It ran fine the rest of the trip. I took it out yesterday, and it did the same thing, but wouldn't get up on plane for about 30 minutes. Sometimes the engines surges, but most of the time, it just seems like a loss of power. Once the engine started running good, it was fine the rest of the day.

I suspect I have a fuel flow issue. The previous owner said a marine shop installed the electric fuel primer pump to solve a wot issue. I would like to simplify everything and go back to a manual primer pump system, and change the electric fuel tank selector with a manual valve. The electric pump is a Carter 4070 which is rated at 4 - 6 psi output & 72 gph free flow. I found a manual for my Mercury that states if a electric pump is used, it should not exceed 4psi max.

I appreciate any suggestion, hints, or advice. I just never seen one run so bad, and out of no where it takes off and runs well oiled machine

[JOE54]

check it over closely [fuel system] if its running lean gonna loose a piston ,check for spark when problem is occurring , would not run it till solved

[careybirdwell]

check it over closely [fuel system] if its running lean gonna loose a piston ,check for spark when problem is occurring , would not run it till solved

I think it is running very rich. My spark plugs had quite of bit of oil on them. I also found out that both T-Stats have been removed. I wondering if the engine not completely warming up could be some of my issue. Both times that I put into the lake, water temp was about 55. Does the ECU control fuel delivery based on operating temp???

[WB]

double post

[WB]

Had the same problems. Would run great and then it would lose power to one or more cylinders getting on plane. If this describes your problems the answer to your problems is your voltage regulators. Buy OEM not cheap China crap. I chased this ghost for 6 months. THe VR are causing all your rich fuel problems also. It is all tied together with false signals cause by the bad VR's.

[WB]

and I pumped fuel bulb a thousand times..

[Tx 201]

Those ECU units get old and you may have the fuel driver going out. Problem with the 99 EFI motor is several components work together, but you can’t plug it into a diagnostic computer like a newer ProXs to see which component is at fault. Gets expensive changing power packs, regulators, ECU repair etc. mine ended up being ECU. I would suggest get a good timing light and check each cylinder to make sure all are getting spark. Betting it is the ECU dried up a little sitting so long and the drivers aren’t making good connections.

[JOE54]

^^^^^ agree ,sometimes bumping on front of ECU when its running bad if it clears up bad inj driver in ECU

[careybirdwell]

Those ECU units get old and you may have the fuel driver going out. Problem with the 99 EFI motor is several components work together, but you can’t plug it into a diagnostic computer like a newer ProXs to see which component is at fault. Gets expensive changing power packs, regulators, ECU repair etc. mine ended up being ECU. I would suggest get a good timing light and check each cylinder to make sure all are getting spark. Betting it is the ECU dried up a little sitting so long and the drivers aren’t making good connections.

I found your thread earlier, and this seems exactly what mine is doing.