Gas Appearing in bilge

[D2fish]

I have a 2000 Mirrocraft aggressor and having it parked in my driveway I noticed a gas smell. Pulling the deck inspection access to the gas tank I saw no indication of gas from the sending unit, line to the outboard or the fill and vent hoses. Also no indication of gas at the outboard.

I assume the heat of the day caused the fuel to expand but with half a tank why is it leaking. All I can think is the fuel line which is normally on a vaccum was put under pressure of some kind (although the vent seems to be working fine) and leaked into the bilge. I am thinking of replacing the fuel line but that looks like it could be a PITA and I don't want to do this if my thinking is off.

Any Ideas on where the fuel in the bilge could be coming from?

 

[tpenfield]

How does the song go ??? . . . there's a hole, there's a hole, there's a hole in the bottom of the tank.

 

[D2fish]

How does the song go ??? . . . there's a hole, there's a hole, there's a hole in the bottom of the tank.

That is the worst answer I could get, and possibly exactly what the problem is. Replacing a tank would truly bite the big one. The strange part is it stopped leaking once it cooled off outside. Still about 1/2 a tank in there.

 

[dingbat]

I have a 2000 Mirrocraft aggressor and having it parked in my driveway I noticed a gas smell. Pulling the deck inspection access to the gas tank I saw no indication of gas from the sending unit, line to the outboard or the fill and vent hoses. Also no indication of gas at the outboard.

I assume the heat of the day caused the fuel to expand but with half a tank why is it leaking. All I can think is the fuel line which is normally on a vaccum was put under pressure of some kind (although the vent seems to be working fine) and leaked into the bilge. I am thinking of replacing the fuel line but that looks like it could be a PITA and I don't want to do this if my thinking is off.

Any Ideas on where the fuel in the bilge could be coming from?

Did you actually see gas or just smell it?

A 2000 model year boat is long over due to have all the fuel lines replaced. If you think changing fuel lines is a PITA, try replacing a fuel tank.

Its also about the time for the fill hose to dry rot and start permeating fumes through the outer cover. Usually on the outside bend radius where the hose makes the turn going from vertical (fill) to horizontal (tank)

 

[D2fish]

Dingbat, I actually saw the fuel in the bilge. There is a slight opening in front of the tank that I could see in and there was the fuel. I cranked the front of the boat up and drained the fuel out the plug. Got about 1/2 a gallon. The timing was interesting as I was working on the fuel sender gauge when I noticed the smell and looked more intently.

I checked the fill and vent hoses and they were dry as a bone and are almost vertical. You are right it is time to replace those as well. I had an issue last week where the engine would fire up and then die. I used the kicker motor to get in. It seemed starved for fuel which is where my thoughts on the fuel line are coming from. I could not get the bulb to get tight. I tried to drain the fuel by removing the fitting to connect to the engine and pumping the fuel out with the bulb. Once started it should have kept going with a syphon effect but hardly any came out. Never got any meaningful flow out of the hose.


My issue is there was 1/2 a tank for a week and nothing leaked as I was updating the gauges and dashboard for a few days. Then it got hot and I am thinking that the expansion of the fuel did something but there is no way 1/2 a tank would expand that much. I just can't identify where the fuel is leaking from..... By lifting the trailer I got about 3/4 gallon out of her.

 

[Chris1956]

The tank should not leak, regardless of temperature or fullness.

In my experience the fuel tank gauge sender is the most likely leak, but the tank needs to be full or the boat needs to be in use.

What is the tank made of? Aluminum can get pin holes in the bottom rear from water sitting there.

 

[D2fish]

The tank should not leak, regardless of temperature or fullness.

In my experience the fuel tank gauge sender is the most likely leak, but the tank needs to be full or the boat needs to be in use.

What is the tank made of? Aluminum can get pin holes in the bottom rear from water sitting there.

Plastic tank. I would agree with you on the sending unit (as that is why I was looking into the tank, checking to see if it was broken / busted wire. good to go) but it was dry as a bone and only 1/2 tank of gas. This one has got me thinking hard.

Since it has been draining for 10 hours, I guess I will shoot some dawn and water in there, put the plug in, drive around some bumpy roads, and drain it back out.. Hopefully making it safe in there.

 

[kcassells]

Tanks leak. Period.

 

[hugh g]

If it's not leaking from the hoses etc. then it's the tank.

 

[kcassells]

You can isolate the feed, vent etc and do a 2-3 lb pressure test. Confirm the with tank mfg or make and model to see what a plastic tank needs for pressure test.
results should follow.

 

[PC on the Bayou]

I'm thinking it has to either be the tank (maybe a hole half way up the side), fuel line, or fuel pump.

The build-up of pressure in the fuel tank from hot weather, could push fuel out through the fuel lines or a bad fuel pump diaphragm. If this is the case, then there is also a problem with your vent which may be clogged.

I think it is unlikely that the leak would be the sender. The sender is on top of the tank; so, liquid fuel would not leak from there unless the tank was completely full and/or the boat was tilted up where all of the fuel is running downhill to that end of the tank.

If the boat is/was tilted upward, then the fuel could run out of a bad connection at the tank for one of the lines (fuel, vent, fill) as well.

Gas evaporates quickly; so, unless it is dripping, you wouldn't necessarily have a wet hose.

 

[PC on the Bayou]

Also, you may check your anti-siphon fitting / hose barbs to make sure it isn't cracked or has a hole.

Based on your description of the running problem, I suspect a hole in your fuel line or a fitting. Maybe even the pick-up tube inside the tank (although this wouldn't explain the leak).

When I was working on my boat and tried to pump out the fuel tank through the pick-up, I kept getting air bubbles. I replaced my tank, but at a minimum was going to need a new pick-up.

 

[kcassells]

Pressure test like suggested, bubble test is of course your way to find the leak on lines or connections. That would be great!
Unless you actually hear it. If you cap off lines for testing you can eliminate one at a time and or determine the tank is leaking. My go to is the tank is leaking.
Point is you need to start somewhere unfortunately.

 

[Scott Danforth]

its an aluminum boat hull, much easier to rip the floor up than a fiberglass boat as the floor is not structural

 

[D2fish]

Tanks leak. Period.

I see you have a similar version of this boat this is a 94 and since you did a rebuild do you have any thing you would look for when inspecting such a boat?

 

[kcassells]

This getting dumb. Have you done any of the suggested tests?