Hey guys, hoping someone out there might have some insight on my engine troubles. Merc 6.2 2008 model. Engine idles a bit rough and will stall, however, also does restart. Main trouble starts at around 2000 RPM, when the engine starts to "chop", from 2000 RPM to around 500 RPM. The boat has twins, so I can get the boat on plane by running the good engine harder, which would take some load off the bad engine- but the bad engine still won't go over 2000 RPM. Seems electrical, but have swapped just about everything from the good engine, with the same results. Any ideas welcome!

How old was the fuel sitting in the new style gen 3 cool fuel tank? You have too fuel pumps in that tank mounted on the engine one of the pumps could be going bad, Or you have too fuel filters inside that same tank that will get dirty. you should check your fuel pressure to start with. See # 21 & 26. http://www.mercruiserparts.com/Show_...ule%28Bravo%29 Also you will need something like this to check fuel pressure http://www.harborfreight.com/cpi/cta...emnumber=92699. http://www.harborfreight.com/cpi/cta...CategoryID=455

The fuel for both engines is from one tank and never sits to long. I just went out and cleaned then swapped the two cool fuel filters- port/star engines.

The reason I don't think it's fuel related is that it's not "load" dependant. when planning, if both throttles are at the same point- the star engine starts chopping rpms at just before 2000. Now if I advance the port throttle- to plane the boat( to around 4000), then play with the starboard throttle, it stays the same- chops just before 2000. If it was fuel wouldn't the rpms go up on the starboard engine as there would be less load- being that the boat was now on a plane( port engine at 4000)? Does that make sence?

Also, I've got Diacom software, and no code show up.

It is possible you have a problem with the fuel pick-up in the gas tank for that engine.

Last year I noticed when below 1/2 tank and getting on plane my starboard engine would start to cut-out. It ended up that the dip tube on the pick-up came loose and was allowing air to get sucked up into the fuel pump. This caused it to lose its prime and the engine would stumble. It would first show up when getting on plane, like 2000 rpm...

does the stumble go away after getting on plane and running ? I had a float sticking on one of my carbs... loaded up the cylinder then it finally burned all the excess fuel away after 5 mins. my thought,

No, won't get past it.

Did you swap the fuel pumps? New fuel/water separators and inline fuel filters?

I had similar issues a few years ago. Twin 496HOs, but both had same symptoms. No codes in ECU. Ethanol fuel had ruined all that i mentioned above on both engines.

I understand what you are saying, But both engines need to be 100% One engine will not help get the other one going in most cases, You can never rule out the fuel system untill you know for sure it is working right. And the problem with your fuel system is you can test the hi fuel pump up on top of the engine, On the fuel rail, But the hard one to test is the low pressure fuel pump, Because there is no valve to hook your fuel gauge up to. You might need to either rig something up or could go old school and try a vacuum gauge on it, Or trust your eye sight and get a strong clear hose hook it to the fuel inlet hose barb on the side of the fuel PUMP tank mounted to the engine and get a smaller fuel tank and stick the hose in there and have some one key it up a few times and then start the engine and try to see if you are getting a good strong flow with no air bubbels in the line and see if the enging run better now. Do you have one tank running both engines or do you have too tanks? Once you know the fuel is good then you would start looking at the power side of things. Unless you see something not with in range with the Diacom software hooked up in real time then you would go after that.

Austin, let us know what you find out. I am curious.