Front Tank Issues

[happy]

I carry an 18-gallon fuel tank in the front of my lil Ski Mate to assist in extended cruising; I'm running a mid 80's Evinrude 175 that really likes sucking down fuel. In addition, I carry a 6-gallon tank in the back of the boat. I run off the six-gallon tank with no problem. My front tank is where the problem is.
Before I put the tank in the boat I cleaned it out, pulled the pickup, sender and as far as one could see in the tank it was clean. (I expected to have some trash issues). I have a 5/8" vent which is clear, new hose, new fitting, I ran 3/8" fuel line from the front of the boat to the transom into a Raycor spin on 10 micron fuel filter, then the OEM fuel line from the filter assy to the engine. I can run about 10 minutes the first time with no problem, then the primer bulb goes flat, loosen the fuel filter and you can tell there is a vacuum. I tried running with the fuel cap off, same thing, pulled the pickup tube, no trash, cut open the filter, it was clean, rechecked the vent, it was clear. Now I can fill the 6 gallon tank using the primer bulb from the front tank, it pumps quite fine, I then ran an electric pump back at the filter and pumped the gas back into the front tank, I let this run for almost thirty minutes, it pumped fine. I dumped the filter, no trash found. I did make sure that the primer bulb was not installed backwards and that in and out on the filter were correct.
Do I have the primer bulb on the wrong side of the filter? Do I need to run a boost pump from the tank to the filter? Any Ideas?

 

[mateman]

Is the OEM line larger then the 3/8 from the tank. I would think that you would need the same size line throughout the system or at least have the larger line running from the tank to the filter. As has been said here before.... just my 2 cents worth.

 

[happy]

Both lines are 3/8" i.d. Thanks

 

[groundloop]

I have a guess as to what's happening. I'll bet your tank has an anti-siphon valve (looks like a hose-barb but has a ball and spring inside). It sounds like after sucking fuel through the filter, primer bulb check valves, and all that fuel line that the engine fuel pump doesn't have enough oomph left to pull open the anti-siphon valve. You could prove that by temporarily replacing the anti-siphon valve with a plain hose-barb (HOWEVER - you're supposed to have that anti-siphon valve in case your fuel line ever developes any kind of leak so yo don't end up with gallons and gallons of gasoline in the bilge).

Electric fuel pumps are frowned upon with outboards for the same reason, if the engine quits the pump keeps running.

 

[happy]

I have a guess as to what's happening. I'll bet your tank has an anti-siphon valve (looks like a hose-barb but has a ball and spring inside). It sounds like after sucking fuel through the filter, primer bulb check valves, and all that fuel line that the engine fuel pump doesn't have enough oomph left to pull open the anti-siphon valve. You could prove that by temporarily replacing the anti-siphon valve with a plain hose-barb (HOWEVER - you're supposed to have that anti-siphon valve in case your fuel line ever developes any kind of leak so yo don't end up with gallons and gallons of gasoline in the bilge).

Electric fuel pumps are frowned upon with outboards for the same reason, if the engine quits the pump keeps running.

I run an on off valve on the tank, no anti siphon I have always found those to be a friggen pain. I did run the boat today; temperature was 99 degrees, and the usual super high humidity. I removed the tank valve, bypassed the fuel filter, and guess what, the bulb went flat. Out of a whim, I took the 6-gallon tank and moved it forward right next to the front tank and used the front tank hose assembly on the portable tank, guess what the bulb went flat. I moved the 6-gallon tank back to the transom and the issue went away.
I took a short ride back to my old shop and borrowed some clear hose and a thermometer, I ran the clear hose straight from the front tank down the deck to the fuel filter assembly, and thermometer showed 120 degrees under the front deck, the back end of the boat showed 98 degrees. The clear hose did not collapse, however the primer bulb did. Then, I switched the primer bulbs out, same thing again the 6-gallon tank ran fine the other did not. I returned the borrowed stuff back, and one of guys there wanted to go for a ride, so we did. Stopped and purchased some gas, beer and a bag of ice. I didn’t bring a cooler, so we used the splash well where the primer bulb is. Guess what, the problem went away. WTF?

 

[mateman]

Heat causing vapor lock in the line?

 

[happy]

I'm going to splash it later today. I've moved the primer bulb out of direct sunlight and am going to try a Par-max blower in the bow of the boat in an attempt to lower the temperature around the fuel tank. Heck if I could find a way to insulate that splash well, I darn sure use it for an ice chest. Space is a premium on this lil Mate! Not to mention, when swimming grabbing a cold one would sure be convenient! Anybody out there convert thier splashwell to an ice chest?

 

[happy]

Welp, That did't fix the problem, Swapping out the front tank tonight, and run again tommorow.

 

[keith4216]

Anybody out there convert thier splashwell to an ice chest?[/QUOTE]

Seen alot of coolers mounted in the splash well. Sometimes one across the middle or two smaller, ones on each side. Guess it depends on the space you have to work with.

 

[ckmate225]

Have you made sure the vent is clear? Can you pop the vent line off once the ball goes flat and see if its ok? I had a vent line on my old mate that was clogged and it did the same thing.

 

[zstevens]

what bout runnin a hard linr from front tank vs rubber ? or larger dia. since its goin further distance

 

[happy]

The tank swap didn't work either, So we rigged in an electric fuel pump, that solved the problem. So tonight I can pull my buddies tank out and put mine back in. Any one got a cold beer?? Could use about 50 of em.