I just purchased a used boat with a 1995 115 mercury ob. The guy I bought if from said he was having some trouble with the fuel line coming from the main tank. Meanwhile he was running off an auxillary tank. The fuel line connections were no good on the main tank so I replaced them. The motor ran great off the auxillary tank, but it ran very rough off the main tank, bogging down, backfiring, etc. Swithced back to aux tank and the motor ran fine after a minute or so. Is it possible I had some bad gas and/or sediment on bottom of tank causing my problem. Or do you think it was a venting issue or somthing else. Thank you, Mike
TomILL
03-03-2004, 12:46 PM
Sounds like a fuel flow restriction on the main tank you are halfway there. Could be the anti-siphon valve that is threaded to the tank (it is an in line check valve) Could be a bad promer bulb. Not likely bad gas unless the rigg has been sitting a coulple of years or so. Tom
Das Boot 3
03-03-2004, 01:55 PM
I'd replace the primer bulb then work my way back to the tank if that didn't fix it.
And...
My brothers DF70 had the same symptoms and it was the quick disconnect at the motor causing the problems. May not apply because of yours running well on aux tank but might as well check everything. His would sometimes seat and caused a gremlin-like problems for a month.1
I would do the following:
1. Take all of the fuel lines that run from the fuel tank to the motor and throw it away.
2. Use a new piece of hose, connect it to the tank and either suck, pump, or pressurize the tank, and blow all of the old gas out of the tank.
3. Replace the tank, and primer bulb with new parts.
3a. obviously this means new clamps as well.
3b. double check the vents to your tank to insure that they are not plugged. Remember, you can't suck fuel from your tank, if the tank vent is plugged. You can check this by simply using an air compressor to pressurize the tank, and insuring that the vent is letting the excess air out.
If you decide to pressurize the tank, to remove the fuel from the tank, simply plug the tank vent with your hand or other, while you are pressurizing the tank through the filler spout - with an air hose and rag, to plug the hole. It is safe, no sparks, and quickly expels the fuel from the tank.
Simply put a long drain line on the tank, and put into a 5 gallon container.
4. Fuel up the gas tank, and you should be good to go.
On this first fueling, I would only put in 3 or 4 gallons, and try the motor.
If you find that you are still getting a bit of intermittent operation from the rig, I would trailer the boat a bit to "shake up" the tank, and then, put your drain line back on the tank, and redrain the tank. It is possible that there is residual
"stuff - water, particles or other" in the tank, which a flushing will help make happen.
Take care
REW
bill hall
03-03-2004, 03:02 PM
pull the floor up on theboat/ make sure the stand pipe in the fuel cell did not fall off in the tank. if thats ok check the fuel vent on the boat. then run the engine/ if it begins too stall squese the primar bulb, if it runs fine then but stalls then replace the bulb. now this should fix it.
chk your fuel filter for debri and also water .
good luck
bill