Mercury 90hp help needed

[psjr57]

OK, I am at my wits end. I have tried several things but my motor keeps bogging down under load. I have a 2003 90hp Mercury 2 stroke 3 cyl motor. I have placed new spark plugs, new spark plug wires, new inline fuel filter and a new primer bulb. All of these items have been purchased through a Mercury dealer.
The motor has no problems turning on. It idles smoothly. Once I throttle down it gets on plane but all of a sudden it starts bogging down. It will not turn off but according to my GPS I am only traveling 3-5 miles per hour. Now for the weird part, it does not bog down all of the time. I would say 90% of the time. I have checked the primer bulb while it?s bogging down and it remains firm. I have however pushed the key/choke while under way and the motor responds like it wants to take off but it quickly bogs down again. My next step will be empting the fuel tank and then perhaps rebuilding the fuel pump and checking the carbs. Do any of you guys have any suggestions? By the looks of this it seems that this is a common problem with motors of any make.

 

[mikeneal]

Re: Mercury 90hp help needed

Sounds like a fuel delivery problem. Is the fuel line from boat to the engine grey in color? The new ethynol gasoline has been attacking lots of things, and there is a TSB for the grey fuel hose Mercury used that breaks down and puts trash in the system. Other thing is the fuel pump has an upgarded rebiuld kit, same ethanol deal. I woudl start at both those. FP rebiuld kit is pretty cheap (~20 dollars) and the hose is same. If neither of those fixes it try running boat on external fuel tank to make sure anti siphon valve in the tank is not the issue. If then no results then next thing is carb rebiuld for trash in the carbs. Do you have a water separating filter? Not the factory in-line one under the cowl, a second larger water separating filter. If not add one, every boat should have one, IMO.

OK, I am at my wits end. I have tried several things but my motor keeps bogging down under load. I have a 2003 90hp Mercury 2 stroke 3 cyl motor. I have placed new spark plugs, new spark plug wires, new inline fuel filter and a new primer bulb. All of these items have been purchased through a Mercury dealer.
The motor has no problems turning on. It idles smoothly. Once I throttle down it gets on plane but all of a sudden it starts bogging down. It will not turn off but according to my GPS I am only traveling 3-5 miles per hour. Now for the weird part, it does not bog down all of the time. I would say 90% of the time. I have checked the primer bulb while it?s bogging down and it remains firm. I have however pushed the key/choke while under way and the motor responds like it wants to take off but it quickly bogs down again. My next step will be empting the fuel tank and then perhaps rebuilding the fuel pump and checking the carbs. Do any of you guys have any suggestions? By the looks of this it seems that this is a common problem with motors of any make.