200 hp. Mercury Optimax 2000' Won't Run Under Load

[Lizzy K II]

I have two 200 hp. Merc. Optis. that are 2000 year models. On the motor that I am having issues with I have recently replaced the thermostats and covers, installed a new high pressure fuel pump, installed a new low pressure electric fuel pump, cleaned the VST, replaced the fuel filter under the cowling, replaced the water seperator inside the boat, installed a new shift switch, and installed a new TPI. The issue I am having with the motor is that sometimes on a cold start the motor will fire but will rev up to a high speed on its own over 3000 RPM. While this is happening the motor sounds as if it is not firing on all cylinders and I have to turn the engine off to prevent it from revving up higher. Usually when this happens on the third or so attempt to start the motor it starts normally and idles smooth. At this point when I put the engine under a load of about 1500-2000 RPM it will run smooth for about 45 seconds to a minute and then cough, sputter, and reduce speed on its own forcing me to let it return to an idle. It will again run smooth at an idle but will not run at a higher speed for longer than a minute on every attempt. This situation seems very odd to me as I have used a DDT scanner to check the engine for any malfunctions or error codes. All of the onboard diagnostics on the DDT tell me the engine passes all tests within the requied specifications.

Any help or ides on what coud be happening here would be greatly appreciated.

 

[Lizzy K II]

Re: 200 hp. Mercury Optimax 2000' Won't Run Under Load

Is there anyone with any ideas on this problem? Today I tested the air and fuel pressure and they seem normal. I'm at a loss here...

 

[gonefishing1]

Re: 200 hp. Mercury Optimax 2000' Won't Run Under Load

Hi Lizzy K welcome to the board. The best thing you can do is start by doing a search on past posts. You have come to the right place to get all the help you need and some. good luck

 

[Lizzy K II]

Re: 200 hp. Mercury Optimax 2000' Won't Run Under Load

I have done some searches and some more trouble shooting and i notice that the fuel pressure drops right as the motor starts to lose speed. I have already replaced both filters and cleaned the VST. What could be causing this loss in fuel pressure? Collapsed fuel lines? Or could my problem be a fuel regulator or tracker valve? I pulled the line off of the fuel filter intake on the VST and no fuel leaked out. It was dry... I'm just a little confused on how to proceed at this point. Any ideas?

 

[the beast]

Re: 200 hp. Mercury Optimax 2000' Won't Run Under Load

hello. first time on this forum. Have Twin 03 optimaxs with fuel/ electrical problems on stbd motor. Been running irradic last 2 times out, hard start and wont rev properly. The 2-3 second low press pump bump you should hear when ign key is turned but not cranked is irradic . I was told this initial prime sequence should occur every time motor is keyed regardless of the presence of fuel. In my case , it is not. I jumped lp pump and it works fine. Havent looked at hp pump but not sure it matters here. Seems to be issue of initial fuel delivery but i have also confirmed fuel present in vst. I too am baffled . Motor wont even fire up now...changed vst filter and racor filter..primer bulb pulls fuel from tank fine, motor cranks but wont start. Switched ecm 's and ruled that out also checked harness and fuses so what could it be?