2005 Mercury 50hp WOT Issues

[jmh1126]

I purchased a 04 Tracker 18' Pontoon with a 2005 Mercury 50hp 2 stroke 3cyl this Spring. The first time I took the boat out I noticed that the WOT RPMs were only going to 4500 with no extra weight on the boat. I later discovered that the WOT range for the engine should be 5000-5500. I started searching for the issue and found several small items that I thought might cause the issue. On top of the RMP not being in the proper range I started noticing that the engine would go around 5000 RPM for a few seconds if I went wide open all at once from a dead stop after the motor had been off for a few hours and then drop down to 4400-4500.

I found the following small issues that I have now fixed:

- Fuel Line had separated inside (replaced fuel line and confirmed that fuel filter and primer bulb were both clear)

- Fuel Cap Vent was stopped up (cleaned out vent & confirmed good air flow)

- Carb # 3 had some blockage (removed and cleaned all 3 carbs)


After each fix I made a trip to the lake with the same results. I have also confirmed that I am getting good spark to all 3 cylinders and confirmed the the correct prop is on the boat.

When I went yesterday the engine went to 5500 right off the bat when I went straight to WOT and stayed there for about 15 seconds (longest ever) and then dropped straight to 4200 (loaded with coolers, etc) and stayed there for the rest of the trip.

The only last thought I have is the Rev Limiter...
The engine has a factory Rev Limiter on it from Mercury...Could this be going bad and causing my issues???

I am about out of ideas and could really use some help on this one. Any help would be greatly appreciated.

[threeputt]

I would not run the boat until the engine turns at least 5000 RPM's at full throttle. I doubt the Rev Limiter is the problem. . I suggest to you to check the compression on all three cylinders and let us know what the reading are? I think you still have some ports plugged in the fuel system. Did you run ethanol gas? Here’s why ethanol contributes to boat fuel system problems, according to a marine retail bulletin:
Ethanol is hygroscopic, meaning it has a strong attraction to moisture. Ethanol increases the amount of water accumulating in fuel tanks.
Ethanol produces less energy (BTUs) than an equivalent unit of gasoline. Ethanol fuel’s usable life span may be less than the normal length of off-season boat storage -
It will also do a number on your fuel hoses. Pour the gas out your tanks and into a clear container and see if there is water and/or debris in it. I would also suggest you install a water-separator filter in the line. Check the fuel system again. I bet you will find the problem in this area and also just for good measures do that compression test. Tom

[jayman]

wot issues

Squeeze the primer ball when underway if rpm comes back you have a fuel supply issue.