I need some advise with this one

[kagr80000]

Well Im stumped with a problem I have had all year long and can't seem to get the problem resolved.

I have a Volvo Penta 4.3 GL (carb) 190 hp engine in my 97 Four Winns 180 RX and this is what happens.
Boat starts at the dock and runs great all the time never misses a beat running around the lake for and hour or so.

Now we stop and float around for an hour or two and we get ready to take off.
Engine starts right up but if I take right off from when I start it up it gets to plane and just dies.Now it takes alot of cranking to get it running agian but when it does it runns flawless for hours until the next time we stop and float agian.(this should rule out a bad Fuel Pump)

We have narrowed down the problem that the fuel system is leaking back to the fuel tank(installed a glass inline filter to see whats going on) and the carb bowl is going empty before the fuel can get pumped back up to it.
I have changed the Electric Fuel pump,Fuel line,and Anti Sifin valve (one way check vale) on the tank and still have the same result.

What else should I be looking for to get this thing fixed before spring
Thanks Kman

 

[Bondo]

Re: I need some advise with this one

and the carb bowl is going empty before the fuel can get pumped back up to it.

Ayuh,... So What carb are we talking about,..??

I'd sooner think the carb was leaking into the intake, rather than siphoning back to the tank...

 

[chiefalen]

Re: I need some advise with this one

You say the anti-syphon valve is allowing fuel back into the tank?

And you changed it out and installed the new one CORRECTLY?

Check that it is indeed on correct and not got some junk keeping the ball from sealing the valve correctly.

Are you letting the boat idle for 3-4 minutes before you shut it down from running hard?

And are you letting it idle for a few minutes before you take off after you start it.

Are you starting it correctly, bye pumping the throttle once or twice and leaving it in neutral one quarter of the way down the throttle?

 

[kagr80000]

Re: I need some advise with this one

The fuel is draining back to the tank not the intake we can see little air bubbles in the glass inline filter when we watch it after about 20 mins.

Have tried 2 different valves at the tank one Alum and on brass witch was supposed to be better.

If I start the engine and let it idle for a couple of minutes it has no problem getting on plane a running fine.

But I would like to be able to turn key and go if I have to.

This has the Holly 2 bbl carb on it

 

[Bondo]

Re: I need some advise with this one

The fuel is draining back to the tank not the intake we can see little air bubbles in the glass inline filter when we watch it after about 20 mins.

Ayuh,....

I can't see any way that, that is physically possible....

 

[kagr80000]

Re: I need some advise with this one

Yeah me and two other boat dealer mechanics can't figure it out either but even after they have replaced almost every fuel related part on the boat even flushing the tank itself thinking that sediments from over the years were getting into the valve just enough to hold it open to drain the line empty the problem is still there.

 

[Don S]

Re: I need some advise with this one

The anti siphon valve is NOT your problem, and is not there to prevent fuel from going back to the tank. I's a valve only there to prevent fuel from siphoning out of the tank if the line gets broken off and drops lower than the fuel level.
How hot does it get in the engine compartment, it sounds a lot like a vapor lock.
When it doesn't start, are you sure the fuel pump is running? Have you checked?

 

[ziggy]

Re: I need some advise with this one

maybe hook up a remote fuel tank.
eliminate everything prior to the fuel pump...

 

[kagr80000]

Re: I need some advise with this one

Last year I Posted here thinking exactly that (Vapor Lock) thats just what it felt like.
But the engine runs at 160 Degree and 190 Degree at the max never higher even when shut down floating so that sorta ruled out vapor lock accoring to the Four Winns dealer.

The Dealer swears that it is the anti sifon valve and they have replaced alot of them over the years and thats allways cured the problem.
He said the line was completly drained and the electric fuel pump just couldn't pick the fuel up fast enough to fill the seperater filter and get to the carb bowl.
Thats why if I start the engine and let it idle for a few minuite before I take off I have no problems.

Now If I run hard for 20 mins and shut down for say 10 or 20 mins it has no problems starting and getting on plane its only if you sit for like over and hour.

 

[chiefalen]

Re: I need some advise with this one

You say when you let it idle for a few minutes after running hard, shutting it down, and than let it idle for a few minutes after you start it it runs fine what's the problem?

You just can't start a carbed motor and expect it not to stall if you don't give the choke a chance to open.

One thing the needle seat good the bowl should not be draining if the seat is good.

 

[Don S]

Re: I need some advise with this one

You've already changed the Anti siphon valve, and that didn't cure it. The pickup tube in the tank may be sucking air if it's the kind with a plastic tube pressed on the metal fitting.
Even if a new AS valve cured someones problem, that was an accident and didn't cure their real problem, just covered it up.
Like ziggy said, hook it up to a remote tank and see if the problem still exists.

 

[chiefalen]

Re: I need some advise with this one

Never ever supposed to run at 190 how i miss that, i went back to read every post.

Games over.

 

[kagr80000]

Re: I need some advise with this one

Sorry about that thermo opens at 160 never runs hoter then that.

Well Im going to take the boat back to the dealer and leave it for them to figure this problem out.
I have had the boat since 1998 and never had to idle more then a minute before I could take off at WOT with absolutly no problems.

Im sure it's going to be something so simple that has got overlooked thats how most problems like this are resolved.

 

[Howard Sterndrive]

Re: I need some advise with this one

I wonder if you simply have an air leak somewhere in the fuel lines on your fuel pump or engine.

The fuel is running back to the tank because air is leaking in. (thus the bubbles you are seeing)
If the lines are all well sealed, the fuel cannot run back.
Like when you put your thumb over the top of a straw... if air can't get in, the fluid can't run back.

I suppose a second anti siphon valve installed backwards at the fuel pump could be worth a try, seeing as you have a few spares anyways.

 

[JustJason]

Re: I need some advise with this one

We wrote this for scenarios like yours.
Have a gander at this thread. It will answer all your questions on testing a boats fuel system.

http://forums.iboats.com/showthread.php?t=283363

It doesn't sound like a boat side fuel system supply issue, but it is SOP for me to do the tests in that thread before I touch a carb.
It sounds to me either like a leaky carb as Bondo says, or vapor lock (probably caused by heat soak) as Don S says.
After it stalls, and when it starts back up, are you getting a plume of black smoke out of the exhaust?
I know you say the engine does not run that hot. But A heatsoaked engine causing vaporlock can have more to do with the design of the boat, and not necessarilly the engine.
An easy test for that would be to get a wire type thermocouple for a capable digital mutimeter. Run the boat hard for 15-20 minutes. Shut it down and quickly pull the hatch and tape the thermocouple to the base of the carb, seal the hatch back up with the wire hanging out, plug it into your meter and see what the temp rises to. You can try taping it before you run the engine... but it will probably fall off.