twin 95 Mercury 150 carbed. One not making power

I have a 1995 Robalo 2440 with twin 150hp mercurys carbed (OG423303 and OG429567). engines have good compression. I rebuilt the fuel pumps on both. replaced plugs, fuel lines, inline filters, water seperators. the engines idle pretty well, a little smokey (classic 2 stroke). when advancing the throttle to get on plane, one motor reaches 4500 the left motor only goes to 1800-2000rpm. the boat just kinda sleds through the water. you can hear the left motor surge 200-300 rpm up and down, knowing that its not real good for the engine to run at this rpm range, I come off the power. after a few attempts at this, the left motor will finally start picking up rpm and like a super charger came on, the motor finally roars into power. I use the boat for trolling so, i use it as is. I should sure like to have the instant power available to get through some of the inlets and not require 2 hrs to get back from blue water. anyone have any ideas on what is plaguing this engine. all help would be greatly appreciated. Thanks

Re: twin 95 Mercury 150 carbed. One not making power

OK, you have eliminated some possible issues. Maybe the high speed stator winding is bad on the left motor. Maybe the plugs are fouling. maybe you have a bad switchbox? Do a spark test at idle and when the motor isn't working correctly. Inspect plugs for water infiltration.

Re: twin 95 Mercury 150 carbed. One not making power

Chris1956 said:

OK, you have eliminated some possible issues. Maybe the high speed stator winding is bad on the left motor. Maybe the plugs are fouling. maybe you have a bad switchbox? Do a spark test at idle and when the motor isn't working correctly. Inspect plugs for water infiltration.

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I have checked the plugs regularly for fouling or anything abnormal. they seem fine. I replaced both switch boxes and voltage regulators on that engine and the performance didnt change. i have "thrown" alot of parts at it. I have never messed with the stators or the carbs though. I removed the top carb from this engine, inspected and reinstalled. the carb looked clean and the floats and bowl worked and looked spotless so, I didnt go any farther with the carbs. This high speed stator winding, how can I test it? I am an aircraft mechanic, I have alot of electrical testing equipment. I am very green concerning outboards. does this engine work on three at low range and six at upper range? that would make sense. is it possible to just swap these windings and see if it follows?

Re: twin 95 Mercury 150 carbed. One not making power

Spark at high speed is controlled by the Stator's high speed winding. Maybe yours is bad?

Re: twin 95 Mercury 150 carbed. One not making power

You can do resistance check on Stator wires connected to both switch box's.Disconnect the Batt first.May need service manual for specifics.