Mercury 115 HP Fuel Problem

[75TowerOfPower]

I got my boat out form storage and wnet to start it and I can't get my primer bulb to get had or fill up the clearish fuel filter. I replaced the bulb thinking it was bad but that didn't fix it. I have two fuel tanks and I have about 1/2 tank in each and try each to make sure one vent or screen isn't working right. So my question is where do I start next? Fuel pump rebuild? I am going to replace all of the lines tomorrow and see where that gets me.

 

[86RajunCajun]

Re: Mercury 115 HP Fuel Problem

Do this i bet it fixes your problem.

Remove your primer bulb line from your main tank.

Get a small 2 gallon or what ever fuel can and mix your 50:1 ratio oil fuel mixture in that.

Put the fuel bulb hole into the 2 gallon fuel can and pump the primer bulb till hard and primed.

Start your engine and let it warm up to operating temp while fueling from the 2 gallon can.

After it reaches operating temp, re connect your fuel bulb line to your main tank and fire it up on high idle to create the vacuum pressure your fuel pump diaphragm uses to draw fuel from the tank through the entire fuel system.

Think it has to run long enough to draw fuel from the tank. against gravity, fill the fuel water separator, the fuel line and the fuel filter before it floods the carb bowls.

What i did to fix this pesky problem, was add an electric fuel pump to assist in priming. The problem is that the small primer bulb simply does not have the suction power to draw fuel up a line, through fuel water separators and filters. You could pump it for hours and it would simply never get fuel to the carbs.

The fuel pump i used i got from a model aircraft i wrecked a few years back <sad day>. Check in hobby sites and stores and you may be able to rig one up for yourself too!

Flip a switch, listen to the pump run for about 30 seconds and pump your primer bulb 3 times and wahlah! Starts every time.

GL!

RC

 

[billy the bass]

Re: Mercury 115 HP Fuel Problem

I'm having same problems with my 02' 125hp merc and 05' 8hp merc kicker. Before winter hit everything worked fine.. From the main line, 2ft out a 3way valve distributed gas between the two motors with a lot of extra hose. So this spring i installed a Water/Gas separator into the line and got rid of the 3way valve and cut off excess hose. So each engine has 2ft of gas line with bulb installed in middle going to separator and 1ft of gas line from the separator to the main gas line connection. Now when I pump gas from the separator to the engines it feels like I'm pumping air, when I do get some gas in the engine filters most just drains back into the separator. None of the engines will run with out dying unless i run at higher rpm. Should I get longer gas lines or get ride of the whole separator completely?? If nothing else i could get one of those electric pumps eh. thanks

 

[75TowerOfPower]

Re: Mercury 115 HP Fuel Problem

Well i replaced a couple fuel lines and replaced the lines on the primer bulb assembly. It seems like the check valve in the fuel pump isn't wworking because it continues to just pump air and the primer bulb won't pick up any fuel. I think that both of my tanks would go bad at the same time. i am looking for a rebuild kit for the fuel pump and see if that helps any.

 

[75TowerOfPower]

Re: Mercury 115 HP Fuel Problem

Well I got some more time to play with it. I took the fuel pump apart and looked to see if there was anything worng and it looked strong and clean. Since it felt like I was still sucking in some air and not able to hold the pressure i took apart one of my tanks. I drained the fuel and saw the pick up tube sitting at the bottom of the tank. So I unscrewed the gauge/sending unit and removed it and put on a new line using the old filter pick up part. Put it back together and then filled it up with new gas and oil. Put it on the boat and the bam hard bulb and started right up and purred real nice. Thanks for the help guys. I didn't think that both tanks with loose their pick up tubes but they did.