Built-in Gas Tank- "Sucking" sound

[Pete Markantes]

I had a custom built-in gas tank made for my homebuilt 20' wooden boat. Manufactured by RDS Aluminum in Florida who produce custom tanks for Cabela's and others. The 20 gallon tank is 11" high and contains internal baffles

Fuel is delivered through a Perko Combination Fill & Tank Vent.

The tank is installed in the forward storage compartment and the fuel line runs high under the deck at the gunwale to the motor transom through a water separating filter with two outlets, one each for the 60 HP Yamaha 4 stroke and 8 horse T-8.

Problem: Periodically there is an audible "slurping" sound repeating about every minute. It almost sounds as if air is being sucked in through the pickup at the bottom of the tank.

In 65 hours of running the system has performed flawlessly EXCEPT for a one-time occurrence of vapor lock (on a particularly hot, 94 degree day). I don't know if the condition is attributable to the tank/ fuel delivery configuration or not but would like to find out.

Ideas?

[Boats]

Originally Posted by Pete Markantes

"Sucking" sound...

Ideas?

Hi Pete!
I experienced the same sucking sound with my boat...

Check your wallet.

[Pete Markantes]

boats02,

Does that mean I should be prepared to spend a lot to repair? This boat, tank design, etc. are all of my own creation and I'm fairly able to conduct all necessary repairs. If it's the result of faulty tank manufacturing I'd have to remove the tank to return to RDS for repair.

What was your solution?

[fishkisser]

Originally Posted by Pete Markantes

boats02,

Does that mean I should be prepared to spend a lot to repair? This boat, tank design, etc. are all of my own creation and I'm fairly able to conduct all necessary repairs. If it's the result of faulty tank manufacturing I'd have to remove the tank to return to RDS for repair.

What was your solution?

I believe He's reffering to the hole in the water theory... sounds like the tank is venting itself .. It has to vent or the tank would stop supplying fuel to the motors or collapse...Barney

[Pete Markantes]

This is the Perko combination gas fill/ vent that I installed. It has performed to specifications on previous boats.
http://www.fisheriessupply.com/onlin...ct/A01/Ntk/All

[Chrome Bumper]

Air bubbling by the baffles maybe.

[Hunt'nFish]

Pete,
Probably sucking air back through the fuel line.
My metal Tempo tank does it every time I shut the motor off if I forget to crack the vent.
Hunt'nFish

[Pete Markantes]

Originally Posted by Hunt'nFish

Pete,
Probably sucking air back through the fuel line.
My metal Tempo tank does it every time I shut the motor off if I forget to crack the vent.
Hunt'nFish

Hunt'nFish,

I still don't get it. The fill/vent combo is designed to permit proper venting and cracking open the fill cap would allow possible water invasion.The fill is installed on the foredeck where rain could easily enter the tank. Not good.


Previous installations have not presented this issue and I'm trying to ascertain what makes this instance unique.

[Boat Doc']

You are probably hearing the anti-siphon valve releasing. It is located where the fuel line attaches to the tank. Nothing to worry about unless it sticks and the engine runs out of fuel.

[Hunt'nFish]

Good point BoatDoc. Mine doesn't have an anti-siphon.

Pete, I might check to see if the vent hole on that Perko isn't plugged.
Could be that years of old 2cyc oil have dried and plugged it....maybe.
Good luck,
Hunt'nFish

[Pete Markantes]

Good suggestions. There is a possibility of the vent having been plugged with 4200 during installation. I've ordered a replacement to arrive Monday and will report after installing.

Thanks to all, esp. Hunt N and Boat Doc.