gas leak when sitting

jlscjs

Petty Officer 3rd Class
Joined
Dec 15, 2015
Messages
85
Went down to the boat 2006 Yamaha 50 hp 2 stroke today and when I started climbing in and out of it I noticed gas dripping onto the water. It hasn't ran for about 3 days and the temps and been in the 60's and 50's at night. I spent 30 minutes looking for a leak and could not find one anywhere. Started it up, ran it for a while, shut it off and no leaks. Is it possible that the gas is expanding and causing it to leak somewhere? Happened before and never could find a leak once I started it ( and even before I could not find a leak) Driving me crazy trying to figure out where the gas is coming from. I need help please!!
 

robert graham

Admiral
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Apr 16, 2009
Messages
6,908
Is your gas tank one of the newer ventless types?....and if so, is it full?...and if so, is it where the sunlight gets on it? Pressure can build up on these newer tanks forcing fuel past fittings, o-rings, etc. maybe try cracking open the gas cap next time you leave the boat sitting.....
 

Tassie 1

Chief Petty Officer
Joined
Apr 13, 2018
Messages
581
Is it leaking from the motor or the tank?
probably not a good idea to start it either way,
 

jlscjs

Petty Officer 3rd Class
Joined
Dec 15, 2015
Messages
85
Is your gas tank one of the newer ventless types?....and if so, is it full?...and if so, is it where the sunlight gets on it? Pressure can build up on these newer tanks forcing fuel past fittings, o-rings, etc. maybe try cracking open the gas cap next time you leave the boat sitting.....

not sure if it is the ventless type,its a 20 gallon on a pontoon so there is a sundeck that covers it, the only thing that is in direct sunlight is the hose with the priming bulb running from the tank to the motor.
 

tpenfield

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Jul 18, 2011
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17,621
If you noticed gasoline dripping into the water, where was it dripping from? :noidea: Start there to find your leak.
 

jlscjs

Petty Officer 3rd Class
Joined
Dec 15, 2015
Messages
85
If you noticed gasoline dripping into the water, where was it dripping from? :noidea: Start there to find your leak.

looked to be dripping out from the back end of the motor where there is a drain hole. Checked all fittings and the clear filter bulb and cannot see anything dripping.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Most likely is maybe that you have the fuel line connected to the motor and vent closed on tank. It expands and forces the fuel up into the engine. Overflows out and into engine casing. Drains out into either outboard well or water. Never a good situation
 

jlscjs

Petty Officer 3rd Class
Joined
Dec 15, 2015
Messages
85
Most likely is maybe that you have the fuel line connected to the motor and vent closed on tank. It expands and forces the fuel up into the engine. Overflows out and into engine casing. Drains out into either outboard well or water. Never a good situation

I have found out that I have a vented fuel cap on the side of the boat, not sure if it might be sticking sometimes but I cannot find a place to buy a replacement cap. It's a 2006 Sunchaser by Smoker Craft. Hope someone can direct me to a site to buy one. thanks
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,417
A fuel pump delivers far more pressure than thermal expansion in a tank.

Nothing to “stick” on a vented gas cap.

If your leaking fuel at the motor it’s either a hose connection or a needle (float) valve in one of the carbs.

How is old is the motor?

Pull the plugs to see which valve is leaking or sticking
 

jlscjs

Petty Officer 3rd Class
Joined
Dec 15, 2015
Messages
85
A fuel pump delivers far more pressure than thermal expansion in a tank.

Nothing to “stick” on a vented gas cap.

If your leaking fuel at the motor it’s either a hose connection or a needle (float) valve in one of the carbs.

How is old is the motor?

Pull the plugs to see which valve is leaking or sticking

The motor is an 2006 but not used a lot according the previous owner.This has only happened 2x in the past year and both times the boat had been sitting and motor not running. How do I tell by pulling plugs if I have a valve sticking or leaking? I have looked and can never see any of the lines or the clear filter bowl leaking. I have also checked on the carb side and see no sign of a leak anywhere.It only has happened when sitting and motor not running, never been an issue once I take it out on the water.
 
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