2002 Mercury 9.9 2 stroke dies under load.

**Gilera** · 09-04-2021, 04:39 AM

So i thought my problems were due to trying out a larger pitch prop but apparently it was concidence that the issues started at the same time or maybe they were somehow triggered by stressing the engine.

I can start engine first pull. Idles fines but after i give it some revs in drive it dies after 10-20 seconds. When i say it dies, I mean sudden power loss and engine struggling to stay alive. If I keep the revs just above idle it will run but any more than that and it will almost cut out.

Carb freshly rebuilt. Checked vacuum lines for leaks, new impeller, fresh fuel, new plugs.

Plugs are light tan on the electrode and both look the same. On the muffs it idles fine and gives a crisp rev when i crack the throttle plate open, but in the water in gear it wont even hold mid range revs.

Any help greatly appreciated.

**FORBESAUTO** · 09-04-2021, 05:27 AM

Maybe sucking air from the disconnect fittings on fuel line from tank to motor not allowing enough fuel to support the extra load. Hard to test, easiest way would be try another hose or bypass disconnects and see if helps. Can tell at times by watching clear fuel filter if you have one, a normal operating system usually shows around 1/2 full filter when running.

**Gilera** · 09-04-2021, 05:31 AM

Originally Posted by FORBESAUTO

Maybe sucking air from the disconnect fittings on fuel line from tank to motor not allowing enough fuel to support the extra load. Hard to test, easiest way would be try another hose or bypass disconnects and see if helps. Can tell at times by watching clear fuel filter if you have one, a normal operating system usually shows around 1/2 full filter when running.

Thanks, yes i was wondering about this and also about blocked fuel hoses but today i was running with the cowl off all the time and the fuel filter stayed full. I also opened the fuel filter before i ran it on the muffs. No crap inside.

**FORBESAUTO** · 09-04-2021, 05:41 AM

Filter full or 1/2 to 3/4 full? All the way full while running normally indicates a problem as long as it’s before the fuel pump on engine, which normally would be on these, if it’s between pump and carb all the way full would be normal.

**Gilera** · 09-04-2021, 05:46 AM

Its before the pump - between fuel tank and fuel pump (fuel pump built in to carb). The fuel filter housing is opaque but it certainly looked full to me when i was going along. I definitely could see it fill up as i was squeezing the bulb after cleaning it when i had it on the stand. What issue would a full filter indicate?

**FORBESAUTO** · 09-04-2021, 06:04 AM

Usually sucking air. I got bit by this on a 115 that had a disconnect on the engine. We where crossing a rough lake and it starting dying out. Didn’t think we where gonna make it back, turned out the beating finished the seals out, and would think one that gets removed more often would be more problematic. The appearance of the half full filter while running is caused by slight pressure drop across filter while fuel is flowing, could be caused from what I’ve seen as sucking air or a blockage.(maybe just filter itself). I would look closely at the filter restricted and those pesky disconnects

**Gilera** · 09-04-2021, 05:20 PM

On these ones the fuel filter has hoses at the top in and out. The fittings dont go down very far. Wouldn't it have to be full for fuel to flow through it?

**25two.stroke** · 09-04-2021, 06:59 PM

Originally Posted by Gilera

On these ones the fuel filter has hoses at the top in and out. The fittings dont go down very far. Wouldn't it have to be full for fuel to flow through it?

No. Doesn't have to be full. But after running a min it should fill up.

**FORBESAUTO** · 09-04-2021, 07:45 PM

May no see the air pocket on that style. Still a good idea to check fuel supply, just looking at filter may not work on that style filter, only works on inline type.

**97mirage** · 09-04-2021, 07:52 PM

My filter remains full when running.
Be sure there are no tears in the small bleed line under the carb. If you recently removed the carb for cleaning and then reinstalled, there could be a small tear where the line connects to the nipple on the bottom of the carb. Also, make sure the ball inside the choke/enrichener assembly didn’t get jammed and stuck up inside the little spring. These are two issues I’ve encountered with mine…not much else goes wrong with these.

**Gilera** · 09-04-2021, 10:02 PM

All right 6 pack of beer and back off with the carb it is. Having trouble finding that vacuum hose as was intending to replace it just to rule that out. The local Mercury dealership told me to ring a hydraulics place as they dont stock it!? Local hydraulics place shut due to covid. Its basically just rubber tubung 1/8" ID right?

One other thing i didn't mention before was that i tried squeezing the bulb when it was struggling to stay alive and it caused it to sputter and die. I guess this flooded it which may or may not be normal.

**Gilera** · 09-04-2021, 10:19 PM

Another question. When i got the engine there was only the patterned O ring between the carb and the motor. The rebuild kit came with a paper gasket of the correct pattern. The exploded diagram seemed to indicate the paper gasket should be there and i was having idling issues at the time. I have both in there now against each other. Does anyone know if this is how it is supposed to be?