inboard fuel tank issue (I think)

tazzvon

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Joined
Sep 22, 2007
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10
I will try to give all the necessary info but forgive me if i don't.

I have an 89 Sunbird Corsica 185 (17.5') with a 4 cyl OMC Cobra 3.0 and matching OMC outdrive.

I can't get it to run off the built in fuel tank more than about 5-10 minutes. The whole thing runs perfectly fine if i drop the fuel line into a 5 gal gas tank. I know this because i have been doing it for weeks now though i don't like it. It runs for long periods (30 minutes or more) when i run it in the drive way off the built in fuel tank but when i put it in the water all i get is about 5-10 minutes before it dies. The boat sat up in a field 5+ years but i drained the fuel tank with an electric fuel pump and whose, filled tank then drained again. I have a fuel/water separator between the fuel tank and the fuel pump. The air line from the tank to the outside of the boat is clear of obstructions. It won't even idle while in the ater more than 5-10 minutes. I keep checking the fuel/water separator but only maybe a 1/4 inch of water when i pour it into a mason jar.

I just don't understand what the difference is from land to water. I even lower the prop on land and shake the boat to move the fuel but it runs fine.

Any ideas would be welcome except the idea to replace or get rid of the boat, this is not an option.
 

alldodge

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Mar 8, 2009
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I can't get it to run off the built in fuel tank more than about 5-10 minutes. The whole thing runs perfectly fine if i drop the fuel line into a 5 gal gas tank. It runs for long periods (30 minutes or more) when i run it in the drive way off the built in fuel tank but when i put it in the water all i get is about 5-10 minutes before it dies.

drained the fuel tank, filled tank then drained again.

Could you explain how the drain, fill and drain again took place? You drained old gas out, then filled with NEW gas and drained again?

I have a fuel/water separator between the fuel tank and the fuel pump. The air line from the tank to the outside of the boat is clear of obstructions. It won't even idle while in the ater more than 5-10 minutes. I keep checking the fuel/water separator but only maybe a 1/4 inch of water when i pour it into a mason jar.

Your still getting water out of the tank after draining twice?

I just don't understand what the difference is from land to water. I even lower the prop on land and shake the boat to move the fuel but it runs fine.

Any ideas would be welcome except the idea to replace or get rid of the boat, this is not an option.

Lower the prop, shake to move fuel and "It Runs Fine" afterwards, more explanation please?
 

tazzvon

Cadet
Joined
Sep 22, 2007
Messages
10
- tank was supposedly empty when i bought it. I put 5 gal fuel in and could not get it to run so i hooked up an electric fuel pump and put the hose in the tank and sucked as much as i could. I thought it was good after that and i installed a fuel/water separator to be sure. Filled tank this time thinking all would be good and there was evidently still water in the tank. ran and drained the fuel/water separator multiple times till no more water or so i thought.

- i must not be getting everything out with my electric fuel pump and hose but don't know any other way to do it as there is nothing but the little hole the fuel level float goes into.

- on the trailer i am able to lower the prop almost all the way down to mimic being in the water (don't know what difference this makes but i am lost). while the boat is running on the trailer i rock the boat back and forth to mimic movement like i am in the water. I am basically trying anything as i don't understand why it runs fine on the trailer but not in the water. Makes no sense. Just got done running it on the trailer for 45 minute without missing a beat. Idles great. Also tried running at 2000 rpm for a minute or two.

Any Ideas?
 

Lou C

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Joined
Nov 10, 2002
Messages
11,803
anti siphon valve on the gas tank (it is a valve that the fuel line from the pump, is attached to at the tank). spring loaded ball to keep fuel from leaking if that fuel line leaks. sometimes the ball inside freezes up due to corrosion.
Fuel tank pick up inside the tank could be clogged with debris
 

tazzvon

Cadet
Joined
Sep 22, 2007
Messages
10
removed the AS valve and it seems ok. Not really sure how to tell but i will probably replace it anyway. Cannot get the elbow that goes into the tank for the fuel pickup to loosen. not sure what to expect when i do get it off as i have never taken one off. Not sure if i will lose parts inside the tank or what. Also don't want to break anything as it is pretty tight but fuel pickup may be an issue.

Still don't know why it runs great on trailer but not in water?
 

alldodge

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Mar 8, 2009
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Agree with Lou, replace your anti-siphon valve, their cheap

http://www.iboats.com/Moeller-Anti-S...view_id.392106

Its probably the water along with the pickup, siphon valve, or vent. Your using very little fuel reving the motor on the trailer. The motor might use a 1/2 ounce of gas reving to 2000 rpm's, and will use 8 to 10 ounces in the water for the same period turning the prop.
 

alldodge

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Mar 8, 2009
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If the pickup tube unscrews then maybe it will come out, but beware they can also snap off, don't force it.

Could also remove the fuel sender to get a larger hole so you may be able to direct the siphon tube. Be safe, get plenty of air blowing using a fan from a distance and turn lights ON/OFF away from the tank and only use battery powered self contained ones.
 

GA_Boater

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May 24, 2011
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on the trailer i am able to lower the prop almost all the way down to mimic being in the water (don't know what difference this makes but i am lost).

Are you running the motor with the drive tilted up? You should only run the motor with the drive down - Your U-joints will last longer..
 
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