Fuel delivery problem on a 1983 470 merc cruiser

[fmalott]

i have a 1983 thunder craft with a 470 merc cruiser when i winterized last year no problems starting i went to put in water this weekend there is no fuel in the line i tried pouring fuel in the carb it starts no problem but i can't get no fuel from the tank so i started from the beginning i pulled the fuel line off the pump poured fuel down the carb motor started pump was sucking so that's not the problem so i put a primer ball on the line i squeeze the ball and i still can't get gas to flow through the line so i made sure line was not cloged no problems there so i kept pouring fuel down the carb but i can't get the fuel to flow from the &$@# tank so i got to the tank the vent is not clogged i took the line off the tank and blew air into the tank it goes in because i can here the bubbles. when i took the line off the tank i got my wife to squeeze the primer ball that i installed and i can feel the suction so now i'm confused, gettin back to the tank i'm not sure if it's original but it's a aluminiun tank it has three holes on top one for pouring gas into it one for the vent and one for gas to go to the carb. now the main question is does the tank have a inline with a check valve or how does the tank work on this make of boat i have never had this problem before and it drove me nuts all weekend luckly i had beer to keep me calm LOL!

 

[fmalott]

Re: Fuel delivery problem on a 1983 470 merc cruiser

taking a better look at the fuel line and notice it's all cracked the fuel line is about 16' long i don't know if this is the problem but i know it's not suppose to be cracked so i will replace the line but i still need to know what's in the tank the fuel line from the carb to the fuel tank attaches to the tank with a brass fitting what's after that i can't see in the tank it's a aluminum tank if i knew this i should be able to fix it

 

[dubs283]

Re: Fuel delivery problem on a 1983 470 merc cruiser

there is a check ball valve at the tank fitting (most boats) that is called an anti-siphon valve, by blowing into the tank and hearing bubbles it sounds as if the ball valve has been removed from the barb fitting - pull it off and check

you should be able to remove the pick-up tube as well and check for blockages

here is some more info on the boats fuel system:

http://forums.iboats.com/showthread.php?t=283269

 

[Raystownboater]

Re: Fuel delivery problem on a 1983 470 merc cruiser

It sounds like one of two problems. Either the fuel pump isnt working or its working but not able to suck fuel out of the tank. One quick test would be to buy a cheap electric fuel pump at autozone and connect it to the line entering the fuel pump from the tank. If you get gas to the carb, your fuel pump is most likely bad. If you dont get fuel, the issue is in the line or the tank. Im not sure what setup you have but in my tank, the sending unit can be removed (the larger of the three holes) and that is also the pickup for the fuel line. There could be a blockage somewhere that just needs cleaning. I would try the electric fuel pump first to see its something as simple as a fuel pump

 

[fmalott]

Re: Fuel delivery problem on a 1983 470 merc cruiser

as for the fuel pump i pulled the line off and poured gas in the carb when motor started there was suction but maybe it's not enough i don't know i also put a primer ball on the line and i squeezed until my hand fell off but still no gas i even got this pump you attach to a drill i use this to winterize my camping trailer and works fine but still no gas i'm going to take the tank out of boat and inspect better the fuel line from carb enters from the top so where is the check valve when i rebuilt my snowmobile fuel tank i had to put a fuel line about 8 inches long with a check valve on the end and it lied on it's side on the bottom of tank is this the way a boat tank should be

 

[fmalott]

Re: Fuel delivery problem on a 1983 470 merc cruiser

i found the problem the check valve in the tank was defective i took the check valve out and didn't replace it do you have to have a check valve i put a primer ball on the line to stop back flow is there a law saying i have to have one or is it just to run better it runs great with out one

 

[dubs283]

Re: Fuel delivery problem on a 1983 470 merc cruiser

you just removed a safety feature that is installed on all inboard/sterndrive boats with permanant mounted tanks called an anti-siphon valve, and yes it is law that it be installed at the factory

you can be legal again by installing a new anti-siphon valve at the tank or a shut-off valve at the tank

a primer ball should not be used on a sterndrive/inboard - it is not needed if all fuel systems are working properly

 

[fmalott]

Re: Fuel delivery problem on a 1983 470 merc cruiser

ok then i think i will go with the shut off valve at the tank i love this forum you learn something new everday

 

[Don S]

Re: Fuel delivery problem on a 1983 470 merc cruiser

ok then i think i will go with the shut off valve at the tank i love this forum you learn something new everday

Bad idea. Consider for a minute if a fire were to start in your engine compartment. Are you planning on going back there and shutting the fuel valve off?? I doubt it.
Put a new antisiphon valve in. They are cheaper than a shutoff valve and work better in case of an emergency.
The primer bulb is not an antisiphon valve and will not pass any fire codes inside an engine compartment.
You seem to be working awfully hard to keep from using the proper part, why is that?

 

[fmalott]

Re: Fuel delivery problem on a 1983 470 merc cruiser

i used a primer ball just because of the fuel delivery probelm but now i don't need one because i eliminated the antisiphon valve and got good fuel flow i'm not trying to not use proper parts i'm just taking advise from this forum, dubs283 said it's ok to use a shut off valve. Don S i understand what your saying and it's great advise but my fuel tank is at the bow and of coarse the motor at the stern so the shutoff would be right beside me under the dash so i think it's not a bad ideal for a shutoff now if the tank was at the stern also i would not put a shutoff there i would put a antisiphon valve. once i know everything is ok i will take the primer ball off

 

[DACEAC]

Re: Fuel delivery problem on a 1983 470 merc cruiser

I would go with what Don says> Have yet to read where he told anyone the wrong way to do something

 

[fmalott]

Re: Fuel delivery problem on a 1983 470 merc cruiser

i agree i failed to mention tank is at the bow if fire starts i can still get to shutoff because it's at the bow the question is! is a shutoff at the bow any better and still safe

 

[stonyloam]

Re: Fuel delivery problem on a 1983 470 merc cruiser

And if a fire starts under the dash????

 

[fmalott]

Re: Fuel delivery problem on a 1983 470 merc cruiser

well if there is a fire and my fire extinguisher can't put it out i hope i have my life jacket on and i'm jumping