Bogging - flooding sometimes starving

[BarryTurano]

Still having issues I am now running 2 separators fuel is clean carb screen is clean. Was having a starvation problem at WOT. Changed out the fuel line (made it a little longer) think that has corrected the starvation at WOT. Started the boat up on Friday black smoke (first time in a long time that happened) burned off fairly quickly. Motor seemed to run well no bogging. Fished a tournament on Saturday motor seemed fine. Went to the weigh in leaving motor started right up but could not get past 3500 rpm's with out bogging down. Noticed my fuel consumption went from 13gph to 17gph at same rpm. Today I called the shop that rebuilt the new carb (Chinese parts were replaced) he thinks it maybe the fuel pump check valves sticking sometimes to much pressure because when it bogs I smell raw gas, or not enough pressure causing starvation and not allowing full rpm. It is very hard to diagnose because it is such an intermittent problem. I need some advice before I go back to my submarine training and calibrate it with a "crescent hammer", never use force on any inanimate object... just use a bigger hammer.
The fuel pump was changed when I first got the boat and I was fighting a "bad fuel" problem. The fuel was in the tank for about 3 years. I had it pumped and have run about 800 gallons of fuel over the last year and a half. I know all the bad stuff is gone now. Do yall think I'm on the right track?

 

[alldodge]

Others may know what you have but other like me don't know what your working on other then its a VP.

A carb won't go lean, back to flooding and then back to lean. You said fuel pump was replaced so unless its clogged back up from sludge in the tank, I'm not leaning that way yet. I'm leaning toward the carb or a restriction in the fuel line. Fuel pumps don't go back in forth with high/low pressure

 

[BarryTurano]

Sorry it's a 1999 VP 5.0GI which is now carbed. As far as the starvation problem I think I solved it with a new longer fuel line. The old line was a little close to the fitting and had enough of a sharp bent that I think would cause a slight restriction. The biggest issue at this point is the bogging down, which is not constant and varies in severity. As I said when it bogs down I an going up on the throttle. If I back off it will catch up to itself and as I said in the original post, when it bogs down I smell raw gas not exhaust but gas as if I were pumping into the fuel tank. The fuel pump was the first thing that was replaced way back when. I'm hoping that the sludge did something to stick or slow down the check valve operation. It's just strange sometimes it will run fine. Other times when I let it warm up and leave the dock it's bad. Saturday it started off great. Later on it was not the same motor. Nothing had changed except shutting down for 20 minutes. Very frustrating.

 

[alldodge]

As far as the starvation problem I think I solved it with a new longer fuel line. The old line was a little close to the fitting and had enough of a sharp bent that I think would cause a slight restriction.

Maybe but my jury is still out

The biggest issue at this point is the bogging down, which is not constant and varies in severity. As I said when it bogs down I an going up on the throttle. If I back off it will catch up to itself and as I said in the original post, when it bogs down I smell raw gas not exhaust but gas as if I were pumping into the fuel tank.

This leans me to think your flooding. Flooding happens most often with either a needle seat, not seating, or float level incorrectly set. Throttling back reduces the need for fuel and the engine to catch up a bit.

I'm leaning toward a dirty or incorrectly rebuild/adjusted carb. Could be a fuel pump issue but need to see what pressure its outputting at idle and higher rpm to tell

 

[BarryTurano]

Think I may have found the problem, will know for sure tomorrow. When I went from throttle body injection to carbed. The fuel pump was not changed. The fuel pump psi for the carb should be between 4 & 6 psi. The low pressure pump that was on for the throttle body is putting out 16 psi. Almost 3x what is required over pressurizing the system?! Changing it out tomorrow with a 4 to 7 psi pump. Crossing my fingers, toes and eyeballs. I'll post up results.

 

[Bondo]

Ayuh,.... That's probably the problem,...

Yer better off runnin' just 1 fuel separator filter, 'n changin' it more often, than runnin' 2 filters,....

Way more places for a vacuum leak in the system,....

 

[BarryTurano]

It's somewhat better. Does not bog down when throttling up. But it seems to lose power and then pick up again at WOT. Checked distributor rotor found one of the magnets sticking. Freed it up but did not help. Tried running on port tank only and stbd tank only same results. Pulling carb off going back to the re-builder for a bench test. The saga continues.

 

[BarryTurano]

Fuel pump helped somewhat. Boat does not stumble when throttling up. At wot boat starts to starve then catches up. Took off the carb. I brought it to the carb shop he bench tested it and it was fine. He feels the problem is choke related. Being it is an electric choke it may lose voltage and close up. Which is why it being intermittent. He suggested I run a carb without a choke. I asked what that would mean he explained that I would need to pump the throttle a few times on a cold start and let the motor idle at about 1100 rpms until it starts to warm up then pull back on the idle. That is what I am doing now. He also suggested he could disable the electric choke and it could be re-installed. I have lost all confidence in the carb from National. I am having a new rebuilt carb being made without a choke. I feel as if I am going to change the boat name to Dr. Jekyll and Mr. Hyde. You never know who is in the motor box. Hopefully this will have a happy ending next week. Fingers still crossed.:frusty:

 

[alldodge]

I think your carb guy is full of BS. If the electric choke was the problem the replacing the electric choke would fix it.

Sure like to know how the carb is "benched tested"?

 

[BarryTurano]

It was bench checked with a vacuum system. The electric choke (he thinks) is losing voltage from a bad connector or poor power connection. I think that would explain the intermittent happening. At least I hope so.

 

[alldodge]

All the best, hope it works out for ya

 

[BarryTurano]

Thank you, me too.