highspeed problem : Throttle dropping out

Ok, so I finally got my boat to idle perfectly and it does great at low speeds. I cleaned out the gas tank and all the gas lines, and now I am having trouble when my boat is going faster than 20mph. It goes good, then when you reach about 20 it's like the throttle drops and the boat will die. What could be the problem, is it my fuel pump, or could it be something else. Also how do you pressure test a fuel pump and what should it be at?

I don't think it's air in the fuel lines, but I do agree it has something to do with the fuel getting to the carb.

Is the timing set too high?

let me be a little more clear. I was having the issue before I cleaned the tank/fuel lines, it didn't happen after I cleaned them.

If you werent having this issue before you must have reinstalled something the wrong way. Recheck all you did, if not, there are many things you could try in order to find the problem.

1-When you first cleaned did you find anything odd? maybe it's running richer now and it just needs a tune up. is it backfiring?

2-Check each section of the fuel line is correctly installed allowing good flow.

3-Take each section out and blow to check for any obstruction (the problem in my old boat was a piece of plastic bag just between the fuel filter and the tank). These would be tank to filter, filter to pump, and pump to carb.

4-Clean the water/fuel separator

5-Take the fuel pump line to the carb out and crank the engine a bit, it should start spitting fuel, so don't point the line to your eye!

You could also take out the inline hose to the pump and place one finger at the inlet to check if it's working on vacuum.

Try all of this, either way it cant be worse than it is now. wish you good luck

ok, i guess I need to be a little more clear. The reason that I took the tank apart was because this was happening, and I figured it was gunk in the tank, getting through to the hoses. So I cleaned the hoses and the gas tank and it is still happening.

Luchog - Found nothing odd in the tank, just those black balls that is made from gas.
Fule lines are connected correctly and nothing is blocking them.
The water/fuel seperator's container busted last week, so I have bypassed that (don't see how that could be the reason though)
and I am getting gas to the carb.

Eric - I did look at the anti-siphon valve and it's clear.

I also put a tester up to my fuel pump and it's working, putting out 7 pounds.

Could this possibly be the carb?

hold on...MC??? I told my Priest over the weekend that i would never even say that word or even think it   lol

yea, sorry guys, it is a '82 2001. So that would be a 351 windsor with a holley carb.

will check to make sure the strainer isn't clogged up, but i'm almost positive I would have got that already.

ok, so I still can't seem to find the problem.
no gunk in the carb or fuel lines.

is 7 pounds of pressure too much coming from the fuel pump? If so could that be the problem?

any other ideas?

I thought is that there is a air leak in the fuel line on the suction side of the pump. At low speeds, the pump can keep up. At high speeds, which means high fuel demand, the pump is sucking air into the fuel line and starving the carb of fuel. As soon as the carb bowl(s) run dry, then engine will want to die.

This happened to me and ended up being the improper sized hose clamp around the thick marine grade fuel line. The clamp was not exerting even pressure and thus air was being suck in at the in-line fuel filter. Once I replaced the clamp, the issue was gone.

Not necessarily. The point was that you need to look for possible places that air can be entering the system...whereever and however. I just gave the clamp scenario as that is what happened in my situation. The point is that the fuel pump was sucking air and not enough fuel and thus starving the engine under load. With the very thick rubber marine fuel lines, it is imperative that the proper sized hose clamps are used. otherwise, the clamp will not exert even pressure around the hose.

It could also be a kink in the fuel line or some other type of restriction.

If you can catch the engine and quickly keep it from dying by pulling back on the throttle, then I think this supports this scenario. If not, it may be ignition related.

Brandon,
I think a fuel pump for a carbed engine should be putting out 5 to 5 and a half pounds. 7 pounds doesn't sound bad, but still may be a little high. Any more and the pump will keep the needles off the seats in the float bowls and just keep flooding the engine. Is that an original pump or a new aftermarket? The problem you're having sure doesn't sound like a over pressure pump issue though.

Explain about the fuel filter/water seperator container busting. What's that all about? Something just doesn't sound right about that statement! You have it bypassed now, but I would want to know why it busted in the first place. When it busted what contaminants did it send toward or into the carb? Please explain.

Hmmm...I did not read carefully. A busted water seperator...I bet it was water saturated and then froze over the winter. If it was immediately notice and replaced prior to attempting an engine start, you should be fine. If not, it may have sent trash downline and thus a restriction limiting the amount of fuel being delivered to the carb at high engine speeds/loads.

Now, if the seperator was saturated, then it stopped doing it job and allowed water to reach the carb. This can cause other problems such as setting up corrossion in the carb. Once corrossion starts in the carb, you might as well throw it away. However, corrossion in the carb usually causes needle valve fouling and thus flooding out on idle. Not usually a high speed/load issue.

My suggestion: Starting at fuel pump, use pressurized air and blow back through the fuel line into the fuel tank (make sure fill cap is off and any in-line filter is/are removed). Replace fuel pump and in-line filter(s). Do the same with the hard line between carb and pump.

Here is a part I am not familiar with, but seem to remember reading about. If the pick-up tube within the tank is loose or sucking air, you will have a hard time finding it, until you remove and inspect. how to do this and can you do this...I do not know. Anyone?

just an update.   

It was the fuel pump, once replaced it started running like new.