2002 Mercury 9.9 2 stroke dies under load.

[Gilera]

Apart from the slightly torn end of the vacuum tube there was nothing much in the carb. Ill replace the vacuum line if i can find some and try a different fuel tank with new disconnect and a fresh batch of fuel.

[LakeFever]

I’ve had issues like this a few times over the years. I find it’s the best move to replace every single rubber line and hose on the entire motor and fuel system. Tygon fuel lines for the little ones are available at Home Depot in any size I’ve needed and I buy bulk fuel line 1/4, 5/16, and 3/8 which covers the rest typically. Don’t forget the pick up line in the fuel tank they can crack and cause this as well. Hope this is of some help

[WaterZebra]

Get Tygon fuel line tubing online. Rubber gets soft and spongy over time.

[Gilera]

I can get Tygon fuel line in 2.5mm diameter (approx 3/32"). The tubing that came off looks more like 1/8". I have seem mixed references to the genuine part being 1/8" and 3/32". As long as it is a tight fit and can deliver pulse it shouldn't matter?

[LakeFever]

I doubt that will matter much. A leak free line is way more critical than slight dia differences. You got to be a little careful with tygon because it gets really floppy when it’s hot so make sure it’s routed well and check it out after running it a few times make sure it’s not wiggled itself into somewhere awkward

[Gilera]

I doubt that will matter much. A leak free line is way more critical than slight dia differences. You got to be a little careful with tygon because it gets really floppy when it’s hot so make sure it’s routed well and check it out after running it a few times make sure it’s not wiggled itself into somewhere awkward

Thanks. I have replaced all 3 parts of the bleed hose with Tygon and also other fuel hose from disconnect to filter and filter to carb with good quality usa made hose. Took out paper gasket between carb and motor and just left o ring. Carefully checked fuel hose from tank to motor including cutting off the connectors to inspect inside of hose and replacing connectors. Got an auxillary tank and pulled out fuel pickup and carefully checked. Cleaned out tank and fresh 95 octane fuel with quicksilver oil. Cleaned out fuel filter and replaced. Just need to get it back in the water now and test. Hopefully it runs better.

[FORBESAUTO]

Just had to post lol. Our generator we are running on we crazy and wouldn’t hardly run this morning at 5:30. Realized it was fuel related and looked at in line filter and noticed full to the top. Pulled it off and back flushed it and low and behold went back to running good and the crazy thing running appearing to 1/4 way full. For those that think ive lost my mind lol.

[LakeFever]

I had a 72 Oldsmobile cutlass eons ago and installed the glass see through fuel filter ( it was the thing to do back then ) and to my shock it barely had any fuel in it when running. It looked like 10 or 20 percent full yet that thing ran great. I always thought it strange but didn’t bother looking into it because it ran great. In fact that may have well been the toughest motor I ever had. 350 rocket, turbo 400 trans. Bullet proof

[InjectorService]

I had a similar sort of issue on a 2 stroke 15 a while back. Would start & idle, but if you reved it, it died. I went through the carb etc way too many times, did all the electric tests, finally I just started replacing electronics. Replaced the trigger, and boom, up and running. IT tested good, but obviously something was wrong.

Anyways, all I'm saying is don't rule out electronics.

Blake

[Gilera]

Thanks Blake. Still waiting to test as weather was awful last weekend. If it continues to give me grief then this will give me somewhere to go next.

[Gilera]

Well I got to have two good days of running on the weekend to test the motor. Running like a champ. Glad it seems to have not been the electrics and glad to be able to enjoy boating with the family again. Thanks to everyone for their help.

When I get around to it I might try changing one thing back at a time including swapping the fuel hose back over to the old fuel tank full of fuel. Hesitant to try the larger pitch prop again - a bit like the last thing you ate before getting gastro!! I have left the thermostat out for now but might try it in again later.

Interestingly I used to prime it 3 times and turn to fast idle to start and it would start first pull. When I first tried this on the weekend it seemed to flood it and it took about 6 pulls to start. The next time it was cold again I just turned to fast idle and no prime. It started first lazy pull. I have left he idle mixture slightly on the rich side which makes it a little rough at idle. I didn't get any lean sneezes after coming off the plane on the weekend when set like this. I will also do a test of leaning this off a bit and seeing if it changes anything. I did notice that the exhaust relief valves do go under for a second when the wave catches up from behind if coming of f the plane quickly. This was suggested as a potential cause. This is the only time the ports go under and it is literally only a second or so. The motor seems to be sitting at about the right height with the cavitation plate about 30-40mm below the bottom of the hull. I could prob lift it slightly at some point if I can be bothered. Only way of avoiding the wave is to come off the plane slower.

[Gilera]

After using the motor a few more times, I am wondering whether I do still have a small problem. I noticed that now the bulb does not get hard no matter how many times I pump it. I cannot see any fuel leaking from carb. With the fuel hose disconnected from the motor the bulb is hard so I feel that it is not any issue with the bulb itself. As I said in my previous post the motor is a little harder to start that before but runs well at WOT so if obviously getting enough fuel once started. When it was all apart I checked the needle and float and the little ball bearing and spring in the fuel pump so I don't think it is either of these things. The disconnect to the motor is the same one as I was using before when the bulb did go hard (same fuel line connected to different tank). Any ideas of what could be causing this - air leaks in the fuel hoses that I replaced in the engine? O-ring at the top of the fuel filter canister not sealing? I would have thought these things would result in fuel leaking out somewhere while pumping. Apart from being a bit harder to start and a bit of a rough idle it seems to run fine.