3.0 GLP-B running rough

[orean]

I have a 2003 stingray with the 3.0 in it. To start off the head gasket blew a few weeks ago so I had pulled it off and checked and reinstalled. It cranks up and runs good on the hose but when put in the water and under this load of the weight it runs not so good. It will idle good and you can get up to about 1500 rpm no problem. When you start to throttle up I would estimate about 25% to 75% or so of throttle the engine does not want to take off. The best description I can give it is basically just runs real rough and will not build up power to drive the boat. Now if from idle The throttle is put all the way to 100% the boat jumps up and runs just like intended and gets up to 4500 rpm running 45 or so no problem. After running this speed for a minute it tries to die down to 3k rpm. ITs odd because about 25% to 75% of throttle it runs like crap and doesn't want to accelerate. I felt as though this is a fuel issue but hoping someone has had similar issue and can lead me in right direction. Also could something stemming from the head gasket replacement cause this like valve being out of adjustment. I followed the service manual correctly setting the valves and this is not the first motor I have rebuilt so I am confident in my mechanical abilities. Any help would be greatly appreciated. Thanks

 

[Bondo]

Ayuh,.... Welcome Aboard,.... Sounds like a fuel delivery issue, which coulda been the cause of the head gasket blowin',.....

Have ya checked for crap in the fuel filters,..??

 

[orean]

I suspected it was a fuel problem when it blew the head gasket. I believe it was my own stupidity because I bought the bought used and ran it with the gas in it from when I purchased it. After the head gasket blew I pumped the tank out and started fresh.

I rebuilt the carb last night again making sure I triple checked everything according to the diagrams. I put a 6.5 power valve in it instead of keeping the 2.5 in it based on some adviceni had received to help the mid range stalling. I took the boat to the water this morning and dropped it in the water and let it warm up. After thravelling through the no wake zone I said a small prayer to the water gods and slowly pushed the throttle down so I could see how it reacted. Low and behold she pushed right threw and up on plane no problem. Here I was cruising at 4.2K rpm about 40mph and then it happened.....it started to bog down. It would drop back to about 3k rpms and about 30 mph at full throttle and just wouldn't do anymore than this. The engine did not run rough of excessive vibration and no noises. Also the rpm gauge would start jumping everywhere and I know It was not reading accurately because it would start flucuating between 5k and 6.5k rpm on the gauge. I know this could not be correct because the engine was not surging and there would be no doubt I would know if the engine was running 6k rpm as I am sure it would sound like the entire thing was coming apart. It will cruise all day at 3.5k rpm around 35mph until the fuel runs out but push more than that and the bogging I described starts. Also if I turn boat off for a few minutes and then crank it and go to full throttle it will run wide open as designed for a small amount of time and start bogging again. I read somewhere that the ignition module on the distributor that controls the timing advancement could do this sorta thing if it was going bad. The article said it would mess up once it got hot which could explain wit the boat runs ok at first then bogs on top end and when I turn it off for a minute it works fine again for a minute.
So anyone have any idea what would cause bogging on top end after a short run and by short I mean a minute and mess the rpm gauge also? As a disclaimer in will add I pulled the timing module off while in was doing the head gasket but reinstalled it.

 

[Lawnpro979]

I'm wondering if, It's NOT hitting on all cylinders i read you post 2 times and I have seen this b4. could be an issue at that Point when missing..... I would look at plugs, and then coil.

Hope this helps