fuel vent

beckoning

Petty Officer 2nd Class
Joined
Dec 15, 2010
Messages
161
'89 Sea Nymph Great Lakes Special (tin) with same vintage 100hp Mercury, and 20 gallon gas tank below the rear middle floor. Problem: Fuel primer bulb will not suck gas most of the time. Details: Until 2 months ago, the bulb filled quickly. Slowly, it was harder and harder to fill. Now, after sitting an hour, a day, or week(s) in the hoist, I squeeze the bulb repeatedly, but it does not firm up, thus doesn't prime the motor. However, the engine will start and run after what I thought was squeezing without priming. Attempted solutions: I thought the bulb was faulty so removed it, but it tested OK. New bulb is $20, so don't want to spend $20 and have the same problem. Tried to blow back into the tank, but there must be a check valve at the tank as the tube would bulge slightly, but that is all. Took the gas cap off, and still could not blow back into the tank. However, with the gas cap off, the bulb seemed to prime slowly. I can also suck on the gas line before it connects to the bulb and get a mouth full of gas. Questions:
  1. Is there a check valve between the bulb and the tank?
  2. Could a partially blocked vent cause the bulb to not fill?
  3. Is there a way to open the vent if it is inside the tank without tearing out the floor and removing the tank?
  4. I cannot imagine there is a vent in the screw cap where gas is pumped in since it is in the motor well, close to the waterline, but could there be?
  5. Could the problem (bulb doesn't fill) be caused by a weak, old bulb?
  6. Do you have any other suggestions?
 

Fed

Commander
Joined
Apr 1, 2010
Messages
2,457
The tank should vent via a hose to outside of the hull, look for a fitting on the outside that has a fine 'wire' gauze in it.
The gauze can block up especially in salt water from salt laden mist forming around it.
 

airshot

Vice Admiral
Joined
Jul 22, 2008
Messages
5,393
First I would check to see if tank vent is clear as you stated bulb will pump up with cap off. Then consider a replacement bulb...if more than a few years old might as well replace the entire fuel line and the bulb. Fuel lines can break down from the inside where you can't see and these pieces of fuel line can clog everything including the checkball in the bulb
 
Top