Starting Issues - 9.9 HP Mercury OB

[dougd1]

I have a 9.9 HP Mercury OB motor that I am having some fuel issues with. First of all, it is a tricky engine to start. It appears to be very easy to flood, and once flooded, it simply will not start. To start the engine, I use the squeeze bulb on the fuel line to pressurize it, open the tank vent and use the pull cord. It may start on the first or second pull - if not, I use the priming bulb on the engine a couple of times. The engine may fire (but not actually start) - if it does, I will use the priming bulb again. I don't use the choke, because it never seems to start if the choke is on. Can you flood the engine by simply using the squeeze bulb? I have checked the output from the fuel pump when only using the squeeze bulb - I get a flow of fuel out of the fuel pump, so the carb is getting fuel, but I would have thought the float and needle valve in the carb would prevent any excess fuel from getting into the engine, so I don't quite get why the engine will not start.
Once I get the engine started, all seems well until I am operating at higher revs. The engine will simply stop dead. I can re-start it immediately after this happens, but what would cause the engine to suddenly stop like that? I suspect the fuel filter, but there is no way to check the filter for any kind of blockage. As I said above, I know the squeeze bulb will pressurize the fuel line up to the carb, so does that not eliminate the filter as a problem area? Any help appreciated.
Doug

 

[boscoe99]

What is the model of the motor? 9.9's are not all the same.

 

[brodmann]

The primer bulb fills up the bowls of the carburetor. If your needle and seat aren't working properly, you'll actually pump gas beyond the needle and seat and flood the motor. The best way to test for a flooded motor is to open the throttle up to half or even full throttle and pull the rope one time. This allows lots of air to flow through the carburetor to offset the excess amount of fuel. Not sure why you say you can't check the filter for a blockage. No idea what type of filter you have, but removing it and trying to blow air through it, or spraying carb cleaner through it should be a way to test it. Dying at full throttle is usually a fuel delivery issue. I'd order an OEM carb kit and start with that. Again, if you think it's flooded, try opening the throttle up and pull the handle. If it fires right up and runs at full speed, you've flooded it. If you take off whatever kind of breather or airbox you have so you can see the actual carb, pump the primer and see if gas runs out of the front of the carb. That's an obvious indication that the needle/seat isn't working. Almost all of these possibilities can be resolved with a carb kit and a good video to see what all is in the carb that needs to be cleaned.

 

[dougd1]

The primer bulb fills up the bowls of the carburetor. If your needle and seat aren't working properly, you'll actually pump gas beyond the needle and seat and flood the motor. The best way to test for a flooded motor is to open the throttle up to half or even full throttle and pull the rope one time. This allows lots of air to flow through the carburetor to offset the excess amount of fuel. Not sure why you say you can't check the filter for a blockage. No idea what type of filter you have, but removing it and trying to blow air through it, or spraying carb cleaner through it should be a way to test it. Dying at full throttle is usually a fuel delivery issue. I'd order an OEM carb kit and start with that. Again, if you think it's flooded, try opening the throttle up and pull the handle. If it fires right up and runs at full speed, you've flooded it. If you take off whatever kind of breather or airbox you have so you can see the actual carb, pump the primer and see if gas runs out of the front of the carb. That's an obvious indication that the needle/seat isn't working. Almost all of these possibilities can be resolved with a carb kit and a good video to see what all is in the carb that needs to be cleaned.

Thanks for getting back to me. Will look at all those issues you identified. I have an in-line fuel filter on the suction side of the fuel pump. It has a clear body and I can see the filter element. It looks fine, and if I use the squeeze bulb on the fuel line, I get fuel coming out of the discharge of the fuel pump, so the filter is passing fuel, but it could also be partially blocked and still pass fuel.
Regarding the engine stopping at higher throttle settings, I have had no issues restarting the motor after the engine simply quits. It will fire up again and run. I seem to have this weird problem of too much fuel when trying to start it from cold, and then not enough fuel when operating at high throttle settings. Motor is a 209 cc motor, serial # OR126144. Thanks again for your help.
Doug