Fuel starvation conundrum

[Lou C]

Ok so all season had a performance problem where the engine was reluctant to plane the boat and max rpm was way low 3800-4000. First I went thru the ignition system & verified total timing advance, then rebuild the Qjet (but no real problems found). Next ran it on the remote tank with fresh fuel and it ran like normal. So that brought me to the boat fuel system. Pulled the pick up tube & antisiphon valve & both were fine. Looked at old fuel line wasn’t delaminated inside. Vent was open. That leaves the fuel, it was e10 fuel stabilized less than a year old. I’m thinking it must be bad fuel since after all that no real problems found! Might have to get the tank pumped. Looked in the tank it looks clean to the bottom. Fuel from fuel filter looked normal. No water, crud etc. Thoughts?
While I was in there I replaced the old pick up tube & anti siphon valve & fuel line. I was surprised it came apart so easily esp since the tank is original 37 years old!

 

[Scott Danforth]

Fuel lasts a maximum of 12 months. Pull the fuel and run fresh in spring

 

[Lou C]

That’s my thought. I may have to get a service to do it for me because it’s about 35 gallons of gas. Gonna ask people I know in the business….

 

[Scott Danforth]

I recently pumped nearly 40 gallons out of my boat. However I switched to an electric fuel pump with the Gen VI BBC. So I just used a bit of hose to run out the boat, a paperclip to bypass the oil pressure switch and turned on the key

You could block the vent use a vacuum cleaner to pressurize the tank and push the oil out the pickup tube if you remove the anti siphon valve

 

[Bondo]

That’s my thought. I may have to get a service to do it for me because it’s about 35 gallons of gas. Gonna ask people I know in the business….

Ayuh,........ What does it Smell like,..??..??

 

[dingbat]

Just a thought…how old are your fuel lines?

Could be a partially collapsed or detached piece of liner. Have you blown out the fuel lines with compressed air from carb end?

Have you installed a piece of clear fuel line to check for a vacuum leak?

Had a similar issue a few years back. Same basic troubleshooting as you. Replaced all the fuel lines while I had everything torn apart but the problem persisted.

A friend recommended checking for air using the clear hose method. Turned out to be a leaking selector valve.

 

[Pmt133]

I'd get a cheap electric pump... pump 5 gallons at a clip and burn it in whatever vehicle I have laying around. If it doesn't smell like crap it'll still run and 5 gallons in a 20 gallon tank won't screw you.... just a thought.

When you ran the test tank, did you bypass the fuel filter head too? Did you also check fuel pressure while running?

 

[Lou C]

As far as vacuum leaks I had the same idea and tested the old (actually well made) pick up tube, no leaks that I could find. It is all alu with the tube threaded into the top fitting, no screen to clog. Today I will rig up a better way to test it with my vacuum pump. The anti siphon valve was just as good as the identical new one I bought to replace it. Tested with the vacuum pump.
The fuel line from the pick up to the filter I cut in half and inspected and it was hard but not delaminated inside. The gas in the tank looks clear & smells like gas.
What surprised me most of all was how easily it came apart. I was prepared for a battle with 3 different penetrating sprays and my home brew ATF & acetone. 5 min and it was all apart. Maybe because the boat is always covered and no rainwater has been laying on the top of the tank.

 

[Lou C]

I'd get a cheap electric pump... pump 5 gallons at a clip and burn it in whatever vehicle I have laying around. If it doesn't smell like crap it'll still run and 5 gallons in a 20 gallon tank won't screw you.... just a thought.

When you ran the test tank, did you bypass the fuel filter head too? Did you also check fuel pressure while running?

When I ran the test tank it was hooked to the regular filter so I assumed that filter & the fuel pump were OK. The boat ran absolutely perfect on the test tank.
Also I changed the fuel filter after spring start up and dumped the contents into a large mason jar & it was totally clear like it’s been every year and smelled like gas. So it’s still a mystery to me that I went thru the ignition system rebuilt the carb (no obvious problem) then ran it on the OB tank it immediately feels better had all of its power back so I thought FOR SURE I’d find a delaminated fuel line, stuck anti siphon or clogged screen on the pick up tube, but none of those things was present! Checked the tank vent too, fine!

 

[Lou C]

Just a thought…how old are your fuel lines?

Could be a partially collapsed or detached piece of liner. Have you blown out the fuel lines with compressed air from carb end?

Have you installed a piece of clear fuel line to check for a vacuum leak?

Had a similar issue a few years back. Same basic troubleshooting as you. Replaced all the fuel lines while I had everything torn apart but the problem persisted.

A friend recommended checking for air using the clear hose method. Turned out to be a leaking selector valve.

Good suggestions I thought the same thing. Cut the old fuel line in half to check for delamination but found none. The filter, pump & steel lines from pump/filter to carb functioned fine when tested with the remote tank.

 

[Pmt133]

I have seen a few times where a worn lobe on the fuel pump will test okay then not generate enough lift pulling up from normal tank height. I don't think that's your issue but maybe?

 

[Lou C]

Thought of that but it ran perfect with the test tank. The use of the test tank reduced the possibilities to:
Anti siphon (tested good)
Pick up tube ((clean no screen tested good but will do more testing)
Fuel line, cut in half to check for delamination found none.
Fuel (unknown).
Only other thing I just thought of could the old fuel line been collapsing under vacuum, but as stiff as it was I doubt it….
Boat is winterized now so no testing till spring but I will speak to my boat yard guy about getting rid of the gas. It’s now about 1.25 year old but was stabilized when I bought it. I have run old stabilized fuel before (when I did the top end overhaul 8 years ago) and did not have this problem. I think that gas was 2.5 years old! Ran fine!

 

[rolmops]

If the fuel lines are from before the year 2000 they might not be completely ethanol resistant. And even if they look good, they might still have very small holes that allow air to be sucked in. Also, what you did not mention is the fuel tank air vent hose. maybe that is crumbling or folding up on itself or clogged with some insect crap. That might just be enough to create a bit off vacuum working against your fuel pump. A friend of mine had a similar problem. It turned out to be a screen over the air vent which his son had accidently painted over and clogged.

 

[Lou C]

Good thought! I checked the vent, I think it's clear, who knows with that old fuel line though. I "think" the hoses were original if you can believe. It's a 1988 boat!

 

[airshot]

The cost of replacing all the fuel lines is a drop in the bucket when compared to all the testing and headaches you are going thru. Had an issue with fuel delivery on my outboard last year. Check the fuel line in various places and it looked fine. After the problem continued, I just said screw it and bought premium fuel line and replaced it all. Just for fun, I started looking at the old fuel line more closely....sure enough there was a couple bad spots !
If you have any over 10 years old, just replace it and be done with it.

 

[Lou C]

I replaced the one from the tank to the fuel filter but I know the fill & vent should be done too…thank goodness the tank appears to be in pretty good shape…

 

[Lou C]

Last question for my iboats friends…anybody know if fuel can be tested to tell if it is still usable or not?
Blackstone Labs does offer a test kit but it’s expensive….

 

[Bondo]

Last question for my iboats friends…anybody know if fuel can be tested to tell if it is still usable or not?
Blackstone Labs does offer a test kit but it’s expensive….

Ayuh,...... I trust my nose,..... if it smells like gasoline, it'll run just fine,....

 

[Lou C]

Ok I’ll have to smell around again some more!

 

[rolmops]

A fairly easy way to remove the fuel from the tank into a fuel can is running a hose through the drainage hole in the transom (where you normally stick the plug) and pull it all the way to the fuel hose and connect it to that hose. On the other end(behind the boat) attach a shut off valve and then a piece of hose that goes in the a fuel can that stands on the ground, so it is well grounded.
Now raise the front end of the boat so all the fuel in the tank will go toward the fuel pick up hose. Open the shut off valve, and create a bit of vacuum ( maybe suck on it) and the tank will empty itself out into a fuel can. If the can is full, turn the shut off valve and replace the can, and so on until the thank is empty. For the last bit of fuel use a different can because it will probably have some dirt and water. All that fuel can go into your car a bit at a time.