2000 5.0 GL intermittent slow acceleration

[Laneman25]

Sometimes when I go to full throttle from idle the engine slowly accelerates. Sometimes it spits during quick accel. I am using this for water skiing so I need quick acceleration. It recently bogged really bad after idling a while while launching the boat. Then it seemed to clear out and do fine. It's almost acting like a 2 stroke that needs to be cleared out. Fresh plugs, clean gas, clean air filter screen, clean distributor cap. Boat came with a 4 blade 14.5 x17 stainless, which I think if anything is too low a pitch, so I doubt it's the prop. Hull is a 19ft bowrider. I believe the standard pitch is 19. I reach max RPM at WOT, afraid to let it go over redline so I haven't tried.

 

[alldodge]

Sounds like fuel, so either dirty carb or weak fuel pump

 

[Lou C]

 

[Donald0039]

Sounds like fuel, so either dirty carb or weak fuel pump

+ 1. Is it carb or EFI?

 

[ESGWheel]

Was it running last season with no issues? If yes, what, if anything was done other then your listed items? When you recently replaced the plugs what did they look like? When it ‘clears out’ does it run well with no issues for the rest of the day? The more info provided the better.

Also, about prop’ing: in general reaching redline at WOT with a normal load is the goal. And agree to not exceed redline but if you are already at redline at WOT unsure what you mean by afraid to go above. Here is some good info about prop’ing link.

 

[jimmbo]

Does it use a Distributor with a Mechanical Advance?

 

[Lou C]

Probably not on a 2000 model year. They used the Prestolite BID electronic and the GM EST.
A GL model should be a carb I think. Prob a 2 bbl or 4 bbl Holley

 

[jimmbo]

my 2002 5.7 with Carb uses a Mechanical Advance

 

[Lou C]

my 2002 5.7 with Carb uses a Mechanical Advance

You must have the Prestolite BID which is basically the same as their points distributor except with an electronic module instead of points. I think the GM/Delco EST was all electronic.
The old GM HEI used back in the '70s and 80s had an electronic module but used a combination of centrifugal and vacuum advance IIRC.

 

[Laneman25]

Was it running last season with no issues? If yes, what, if anything was done other then your listed items? When you recently replaced the plugs what did they look like? When it ‘clears out’ does it run well with no issues for the rest of the day? The more info provided the better.

Also, about prop’ing: in general reaching redline at WOT with a normal load is the goal. And agree to not exceed redline but if you are already at redline at WOT unsure what you mean by afraid to go above. Here is some good info about prop’ing link.

The plugs looked dark. No heavy deposits but the color was dark, not tan. The boat did clear out and ran pretty good all day. Regarding the prop, once I reach redline I throttle back. I don't want to over rev the engine. I think it would if I allowed it.

 

[Lou C]

Are you sure the electric choke is opening & staying open? These need a steady source of 12v to stay open or else they close!

 

[ESGWheel]

The dark plugs + bogging + acting like a 2 stroke that 'needs to be cleared out' leads one to think too much fuel. This is why Lou is asking about the electric choke. This is easy to check > simply start up at the dock with the spark arrestor off and look over time. Been awhile since I have monitored electric chokes but suspect it should be fully off (wide open) after about 5 mins, perhaps less. Another possibility is the float / needle seat not closing off flooding the engine. This could be the float, or the needle / seat or both. This may be also easy to see by idling at the dock and after warming up (assuming the choke fully off) by looking down the throat of the carb using a flashlight. Is liquid gas visible? If yes, the float / needle – seat issue.

Also, you did not say if was running well last season and what is different from last to this.

For the prop’ing: mark with some painter’s tape or know by feel the position of WOT. And when other issue resolved and running good, take it out on a good day with lots of space and slowly creep to WOT. If you get to redline (5000 RPM?) with lots of throttle left to still go, then yes, need a higher pitch prop.