1986 454 Magnum stalling issues

[isp184dude]

My 1986 454 will run fine on the water for the first 20-30 minutes of the day then will start to stall out under load. It will idle just fine but when you throttle up it will stall out right away. I pulled the anti-siphon valve and it looked good, no debris or gunk in it. After re-attaching the hose to the valve it will run fine again for about 5-10 minutes then stall out again. Could it be the fuel pump? Any help is appreciated. Thanks.

 

[Scott Danforth]

check the fuel vent. sometimes insects make nests in the vent plugging it.

 

[isp184dude]

Fuel vent looks good, not plugged.

 

[alldodge]

Try this, run the boat until it does it, then open the gas cap and see if you can run again, might even hear air rush it.

If that doesn't fix anything, get a vacuum fuel pump tester and measure fuel pressure between the pump and carb with a Tee fitting inline

 

[isp184dude]

Fuel pressure is good, I replaced the fuel pump and the anti-syphon valve but still have the same problems, what else should I do?

 

[NHGuy]

Remove the fuel line and blow it out, or even better get a new section. Cheap assurance. Dump the water separator contents in a clear container and check it for junk. Also check the carburetor inlet filter for stuff. Does your fuel get hot? Route it away from heat.
Are your gauges showing normal values? Hot? Oil pressure? State of charge? Is there stuff in the gas tank getting in the pickup? Which then falls off when there's no more fuel demand?
Is the choke staying fully open when the engine is warm? It should.
BTW the fuel water separator is a throwaway part. Not for reuse.

 

[alldodge]

I pulled the anti-siphon valve and it looked good, no debris or gunk in it. After re-attaching the hose to the valve it will run fine again for about 5-10 minutes then stall out again. Could it be the fuel pump?

Fuel pressure is good, I replaced the fuel pump and the anti-syphon valve but still have the same problems, what else should I do?

You have a restriction somewhere. Did you check the fuel pressure with the boat running on plane, or only at idle? I'm still guessing your running out of fuel. Get a gas can and stick the fuel line in the can and try.

 

[isp184dude]

I will try that. Do you think the tank may not be venting right? It is always tough to fill it, gas backs up and shuts off the pump unless you fill it VERY slowly.

 

[alldodge]

It's possible, but there are many boats which the manufacture routed the fill hose so there is a trap in it. In any case using a gas can will tell us if it's in the tank or not

 

[isp184dude]

Update, I had the same problem and ran the fuel line to a 2 gallon gas can I brought along. The boat ran like a champ. So what should my next step be?

 

[Bondo]

The boat ran like a champ. So what should my next step be?

Ayuh,.... Welcome Aboard,.... Yer boat's fuel system has a problem, find the problem,.....

The system consists of the tank, the vent, 'n line, the diptube, the A/S valve, 'n the fuel line to the motor,.....

It's restricted somewhere,....

 

[isp184dude]

The problem is coming from the tank. After it died today I disconnected the line from the tank and put it into a gas can and it ran fine. I'm thinking a vent issue?

 

[isp184dude]

Fuel tank vent issues

I have a 1987 454 magnum and it runs great for 30 minutes then bogs down. Long story short l unhooked the fuel line from the tank and put it into a gas can after it started bogging down and it ran great. As I pulled the line off of the anti-syphon valve I could hear it hissing like it was trying to draw fuel. (I replaced the anti-syphon valve already). I'm thinking it must be a venting issue but how do I solve this? Thanks for your help.

 

[GA_Boater]

Is this a new to you boat or a new problem?

One thing you can try is to open the fuel filler cap when it bogs. If it picks up, tank venting fitting is definitely suspect. If it doesn't, the new anti-siphon could be bad.

A couple of things to check;

Kinks in the vent hose.

Mud dauber nest in the vent fitting.

 

[isp184dude]

No mud daubers, opening the fuel filler cap seems to help, but not much. I wonder if the vent hose is partially collapsed?

 

[achris]

If opening the tank full cap didn't help, it's not a vent problem. Check fuel filters, don't forget the one in the carb, and fuel pump output.

 

[alldodge]

Guess you didn't like the answers you were getting in this thread
http://forums.iboats.com/forum/engi...ives/10191648-1986-454-magnum-stalling-issues

So your trying another one

 

[GA_Boater]

Guess you didn't like the answers you were getting in this thread
http://forums.iboats.com/forum/engin...talling-issues

So your trying another one

And getting all the same suggestions. Again! :facepalm:

The threads are merged.

 

[isp184dude]

My apologies for starting a new thread. I think I have the problem solved, there was a dip in the vent hose causing fuel to create a trap. I appreciate the help.

 

[isp184dude]

I guess it's not fuel related since the vent hose is good, all the filters look good, and the pump is working fine. I took it back out on the water and it did the same thing, died after about 10 minutes. Any suggestions on where to go from here?