1998 merc 9.9 fuel problem??

[bamasteeler]

1998 mercury 9.9 four stroke s/n 0H014563

Went out to lake yesterday for test run of boat and motor. Motor starts up and idles fine, little on high side, seems to b running great up and down lake fin for bout 10 minutes, stop to adjust idle cause its idling pretty fast, start back up idling much smoother. Shifts into forward and reverse a lot better now as well. Start riding again and it just dies!!! No matter what I do I can't get it to stay running, I can twist throttle a couple times, pull start rope, engine starts but then dies as soon as it uses that fuel.

Limped back to buddy's dock on trolling motor, same thing, would only run on fuel I injected by twisting throttle before starting. Walked away from it for awhile, went back pretty much same but started varying throttle linkage inside engine once it started, eventually got it to idle on its own without stalling out. But every time the butterfly would start to open it would stall. Eventually after several attempts of varying throttle linkage I was able to rev engine, could see fuel being sucked in through main jet in throttle throat. Decided to go back out in lake and test it out again.

Idled around buddy's dock area for several minutes with no problems at all. Got out to main channel and got to WOT and everything was good for about 150 yards when I could feel engine start to lose power, eventually stumbling and then stalling!! Pulled start rope nothing happened!!! Cycled throttle 3-5 times pulled rope, started up idled fine. Started off again, same thing...150 yards or so and engine stumbled then died. Decided to give up for the day. Now seeking others wisdom!!!

So why does it idle fine yet go so far at WOT then die? Fuel starvation?? Carb issues? Air issues?

I know I am sucking a little air at fuel line connection on front of engine, not sure if this is cause of it but sure it doesn't help getting air in fuel system. Taking fuel hose back and exchanging it for another.

Sorry so long but just trying to explain everything that was goin on with motor yesterday. I'm new to the outboard world but not new to mechanics. Thanks for any and all help

 

[oldman570]

Re: 1998 merc 9.9 fuel problem??

If the tank vent is not open or is pluged up the fuel pump will cause a vacum in the tank and not ba able to pump the fuel when the vacum gets to high. Any air leak in the fuel system can cause the motor to run lean and can cause damage if it runs to lean. When the motor starts to lose power have you tried to pump the primer bulb to see if it gets the motor to running without dieing? If the new hose fixes the trouble, take a clamp that fits around the fuel hose and mount the primer bulb in a vertical position on the transom with enought slack hose to move the motor full movement side to side and tilt up and down. I have found that it helps keep the added weight of the fuel hose from wearing on the conection at the motor and causing air leaks at that seal pluse it keeps the check ball in the ptimer bulb from being sucked out of the position it should be in. JMO
Oldman570

 

[bamasteeler]

Re: 1998 merc 9.9 fuel problem??

yes tried to squeeze the primer bulb when it started losing power and no change, it still stalled out.

 

[oldman570]

Re: 1998 merc 9.9 fuel problem??

If there is a fuel filter in the fuel system, it could be gettng pluged up and should be cleaned/change out. Other wise it could be that the carb inlet needle is sticking and the carb needs to be cleaned or rebuilt. JMO
Oldman570

 

[snowman48047]

Re: 1998 merc 9.9 fuel problem??

There may be multipe filters too. I always replaced the only one I could see on mine, then after a few years it wouldn't do anything but idle. THEN I found out about that second filter, which was actually the first filter in the fuel system line on the moter.