Mercury 9.9 Hurting my Season: Advice Needed

[Sock Puppet]

I've been chasing an issue with my 2009 Mercury 9.9 4 Stroke since last year. Sometimes it will run perfectly, other times it will run for various lengths of time and 'run out of fuel'; die. I always disconnect the fuel and run it empty when done for the day. My non-venting Atwood fuel tank sits inside the rear compartment, and the hose runs through a bulkhead fitting and to the motor.

Last season I installed a brand new fuel tank and Atwood hose kit so everything was new to the motor. Still had problems. I originally had the fuel bulb mounted perfectly horizontal, and on the advice of this forum I re-routed it to sit at an angle (I've tried angling in both directions). This made no difference. I moved the bulb from inside the locker to the motor well so I could pump it to keep the motor running when it started to die. I drained the fuel with ethanol out of the tank, checked the tube and 'check ball' in the tank, and refilled with brand new ethanol free gas.

I found the lining inside the gray Atwood hose was separating from the hose, so I thought this was restricting fuel supply. I replaced all the fuel line with fuel injection line. I replaced the bulb. I replaced the bulkhead fitting.

A couple of weeks ago it was having issues immediately, and I traced it to an air leak at the fuel hose fitting at the engine. Bingo, right! I replaced the fitting last week and the motor ran perfectly during our outing; even during a storm while we motored back in under load. We went out yesterday, motored for about 25 minutes as there was no wind...then it died suddenly. Pumped the bulb, restarted, and had to 'nurse' it the rest of the day by periodically pumping the bulb.

Checked the fuel level and it is down to about 2.5 gallons (6 gallon tank). My only thought at this point is that the tank sits below the motor fuel inlet, and with lower fuel levels it does not maintain flow, but I don't know.

Below are pics of my installation. I'm open to any/all suggestions. These motor issues are impacting the wife's confidence. She didn't want to sail yesterday when the wind picked up because we couldn't count on the motor (my slip cannot be sailed into). Please help!

 

[Sailm8]

My guess is that you have the wrong fuel plug to the engine. I had the same problem with my Tohatsu. The plug seemed to fit just fine and would work for 2 or 3 outings then die until I pumped the bulb. I thought i had the correct plug but when I check the drawing on a parts list I saw it was slightly different. Bought one and problem solved for over a year.

PS If you pump the bulb can you get gas to drip out of the connection? If yes I think you need a new one.

 

[kloudie1]

Sounds a lot like an air leak at the engine "quick connect" or the pass through on the bulkhead. . It may also be a fouled fuel pump on the engine. The pump is easy to remove and clean... and it has a screen, I think, that may have gray stuff from the hose in it.

 

[Sock Puppet]

Thanks, gents, I'll check the drawing and buy a Mercury OEM engine quick-connect. No fuel leaks out of the current one when I pump the bulb. As the bulkhead fitting is new and the hose fits very tightly and is snugged with hose clamps, I'm nearly certain there is no air leak there. I will, however, check again. I'll also clean/inspect the pump.

Other ideas are welcome!

 

[Benny17441]

New regulations demand portable non-vented tanks. With changes in temperature positive or negative pressure will fluctuate creating problems for the engines. High positive pressure can cause engine flooding while high negative pressure can cause fuel starvation. There are some on demand fuel flow valves to deal with high pressure issues. Just remove the cap and allow pressure to equalize before use. I understand your problem predates the new tank but it will not hurt to verify it is not compounding the problems. Sounds like a fuel flow issue so check any filter or screen between the tank and the carburetor and like Kloudie suggests pay much attention to the condition and operation of the fuel pump.

 

[Zed]

New regulations demand portable non-vented tanks. With changes in temperature positive or negative pressure will fluctuate creating problems for the engines.

What new regulations?

 

[justsomeguy]

New regulations demand portable non-vented tanks. With changes in temperature positive or negative pressure will fluctuate creating problems for the engines. High positive pressure can cause engine flooding while high negative pressure can cause fuel starvation. There are some on demand fuel flow valves to deal with high pressure issues. Just remove the cap and allow pressure to equalize before use. I understand your problem predates the new tank but it will not hurt to verify it is not compounding the problems. Sounds like a fuel flow issue so check any filter or screen between the tank and the carburetor and like Kloudie suggests pay much attention to the condition and operation of the fuel pump.

If I'm not mistaken, the new non-vented tanks have a one way valve that will not allow a negative pressure (vacuum) buildup.

 

[justsomeguy]

What new regulations?

Apparently, the EPA doesn't want us venting hydrocarbons into the atmosphere anymore.

 

[Sock Puppet]

If I'm not mistaken, the new non-vented tanks have a one way valve that will not allow a negative pressure (vacuum) buildup.

I believe that to be the case. The tank will certainly swell up a bit in the heat, but I've never seen the opposite in the cold. During the troubleshooting I've loosened and even removed the fuel cap on the tank and it made no difference.

Any other ideas? If I pull the fuel pump will I need a replacement gasket or o-ring when I go back together with it?

 

[justsomeguy]

I think you've got another slight air leak somewhere.

[ducks the dopeslap]

 

[Benny17441]

Justsomeguy you are correct about the one way valve to prevent negative pressure, perhaps I should have phrased it to insure that the valve was properly working. Have seen tanks that seat OK but while the engine is running it creates negative pressure. Removing the cap is just a simple way of equalizing pressure in the eventuality there was a difference.

 

[Sock Puppet]

I think you've got another slight air leak somewhere.

[ducks the dopeslap]

That settles it then, I'm going to install a Cummins diesel and be done with it.

 

[Benny17441]

That settles it then, I'm going to install a Cummins diesel and be done with it.

Hey the Russians developed and were marketing a small nuclear cell to power an electric motor for sailboats. Consider unlimited range and not having to refuel for years. The glow would come free.

 

[justsomeguy]

I've had the same problem on my little 4 horse 4 stroke Nissan.

New O rings in the connectors, new fuel pump, new carb. Cleaned all the inline filters. The only things I haven't swapped out yet is all the fuel hose.

That's probably next.

 

[Zed]

Hey the Russians developed and were marketing a small nuclear cell to power an electric motor for sailboats. Consider unlimited range and not having to refuel for years. The glow would come free.

Really? Fuel cells run about $4000 for 200 watts. Where is this device?

 

[Zed]

There are some on demand fuel flow valves to deal with high pressure issues. Just remove the cap and allow pressure to equalize before use.

My tank has a little button on the top of the fuel cap which allows me to release or draw in air.

 

[jibes138]

I was having trouble where my 20HP Yamaha seemed to be starving for gas at wide open throttle, it would periodically skip. I mounted my squeeze bulb so it is vertical and haven't had further issues. Also make sure the flow direction on your bulb is going in the direction of the arrow. If it is backwards it will run for a while then starve the engine. Read the following: " Orientation

It is also advantageous if the primer bulb can be position in such a way that during priming it can be oriented vertically, with the direction arrow pointing skywards. This will allow gravity and the weight of the fuel inside the primer bulb to help with the operation of the one-way valves. If the primer bulb is oriented with the flow arrow pointing downward, gravity and the weight of the fuel in the line above the inlet check valve may spoil its operation, and the primer will not work properly.

This subtle but important point—orienting the primer bulb skyward—is often overlooked in many installation, but it really helps the primer bulb to do its job. This trick was shown to me by an experienced Mercury outboard mechanic, after I complained that the new primer bulbs he had installed did not work well. The difference in results is amazing, and just by changing the orientation of the primer to vertical, its operation is much improved. In just a few squeezes it should be possible to fill the bulb with fuel."
http://continuouswave.com/whaler/reference/primer.html

 

[Sock Puppet]

Thanks, Jibes, that is great information and I'll certainly give it a shot!

 

[walt]

I have no idea if this is related.. but I had a primer bulb in about the exact config as you have (same boat) and direct sunlight would get the bulb hot and the engine would die. Maybe some sort of vapor lock?? Simply shading the bulb solved the problem.

I had this issue at 8600 ft elevation which Im not sure matters. I think you are at about 6000

 

[Sock Puppet]

I have no idea if this is related.. but I had a primer bulb in about the exact config as you have (same boat) and direct sunlight would get the bulb hot and the engine would die. Maybe some sort of vapor lock?? Simply shading the bulb solved the problem.

I had this issue at 8600 ft elevation which Im not sure matters. I think you are at about 6000

I remember reading that post, and considered it before moving the bulb into the motor well, but decided it was worth the risk until I made some progress. I'll definitely do something about it down the road.

Yep, I believe my GPS says the lake is at 6100 ft.