'89 90 hp etlf limited to 2300 rpm

Ive been searching the forum for a while now to find some solutions, but im not sure of my next step.

Here's the problem, The engine is not going above 2300 RPM when in the water. Last summer it ran great with new fuel lines, pump ball, and fuel filters/water separator, new lower unit oil, until what became the last trip of the season. While running at speed the engine cut out. It would start back up, run for a minute then do the same thing, if the engine was throttled back quickly it would recover to work at low speeds. The problem progressed so that the engine would only run to approximately 3000 rpm where it would shudder and run very rough. while nearing the dock it worsened so that it would only run above at low rpms. No alarms were tripped, so i was left a little confused.

This spring I had drained the tank and refilled, replaced the fuel filters/water separator, and have cleaned the carbs and changed the gaskets, installed a new water impeller/gaskets, and changed the lower unit oil.

I put the boat in the water this weekend and the same problem - the motor was limited to 2300 rpms. It runs and sounds ok up to this rpm (the last 200-300 rpms seem a bit slow) but otherwise runs fine up to that specific rpm.

I tried pumping the ball while running and no help, levers/choke are not stuck, the check valves in the fuel pump seem fine and the outside diaphragm (screen) looks fine, their doesn't appear to be a problem with gas getting to the carbs. The plugs are fouled top one was wet and dirty with a lot of buildup, and the bottom two were dirty as well. I have the repair manual and i couldn't decipher what the next step to take is in order to isolate parts and find the problem. Any help would be much appreciated.
thanks.

[jb123]

did you try choking while running, if this helps clean carbs again.

do you have any buzzer sounding, does it work?

oil level fine, water pressure good?

because its stopping at that rpm it sounds like rpm reduc.

My problem this spring was very similar to yours. I cleaned the carbs and it ran ok for a short time. The problem was that I still had crap from ethanol in my fuel pumps. I rebuilt them ( very easy and cheap) and cleaned the carbs again. Runs great now. Hope this helps.

i haven't tried choking the engine while running. I will give that a try though. I haven't had any alarms go off and the fluid levels are good. I thought it was kind of odd to have these issues when the fuel lines up to the engine are new as well as having a cleaned fuel tank. Before i started running it i had installed new filters and then had it running good all summer. The problem occurred then i drained the tank, changed the filters and cleaned the carbs and there was no change in the problem. I started pulling the fuel pump apart, one side came off easy and the screen (diaphram) looked clean. The other part seemed to be stuck with the gasket so i didn't go further, I have to price out the fuel pump and see how much for new insides. well see then probably start looking at potential electrical issues next week, after a couple more fuel checks.

[jb123]

if you have the quick release at motor do yourself a favor and remove it, run fuel line directly to filter.