mercury 90 fuel issue?

[jdhgcb]

hey guy's, I've got a 90HP Mercury 2 stroke on my 99 tracker. I assume the motor is also a 99 it's the original motor as far as I can tell. My problem is this. Last time out to the lake, It had a real hard time starting and ended up taking it home do to a serious pluming leak. today, started a bit easier but upon accelerating much over idle it died out. didn't die, just wouldn't gain RPM. now in the past i have been known not to prime the bulb enough, which would make it act this way, and would have to give it a few more squeezes to get it going. but after that it would run great all day. this time, if I gave the bulb a few squeezes when it would die out it would run on all three cylinders for a moment and then back to dying out. each time i would go back to the primer bulb it would be soft and would take 6 or 8 pumps before it would firm up. It felt as though it just wasn't running on all three cylinders all the time, sometimes two, sometimes only one. I fought with it for 20 minutes or so and ended up bringing it home. Any ideas? fouled plugs? I took them out and cleaned them before this trip, (they are NGK gapless plugs) fuel delivery? maybe the pump? Is it sucking air rather than gas somewhere?

I figured you Merc guys would know. thanks in advance.
Joshua

 

[jdhgcb]

Re: mercury 90 fuel issue?

I should probably add that before this, it ran AWESOME. other than me not priming enough. I haven't run it much over the last several months, but when I did i would disconnect the fuel line and run it dry each time before letting it sit.

 

[Lone Duck]

Re: mercury 90 fuel issue?

Are you using a built in tank or a carry on ? If it is a carry on make sure you open the vent. If it is a built in make sure the tank vent is not plugged. If this is not done your fuel pump will make a vacuum in the tank. Causing the fuel to want to run back to the tank. next check all hoses and connections between tank and fuel pump for cracks and leaks. pay careful attention to your bulb . Take your time and tell us what you find. Some will argue with me, but when you run it out of fuel you are causing a lean condition in your engine which will cause unnecessary wear, you are then starting your engine dry.

 

[carholme]

Re: mercury 90 fuel issue?

First of all, what was the serious plumbing leak?

What is the s/n of the engine?

Have you tried starting it and once it starts keep pumping the bulb to see if the engine will continue to run as you advance the throttle?

Gerry

 

[ENSIGN]

Re: mercury 90 fuel issue?

Check the inside of the fuel line.There has been a problem with the gray fuel line coming apart on the inside.The small particles get stuck in any part of the fuel system and cause problems.

 

[jdhgcb]

Re: mercury 90 fuel issue?

Lone Duck: on board tank, vent is clear. I was wondering about the bulb as it will drip a little while priming as it begins to get firm.
Carholme: plumbing leak was through hull fittings as well as the "nipples" on the bilge pump and the live well pump. I did pump the bulb while running and it seemed to help, sometimes a little, sometimes enough to make it run fine for maybe 15 to 30 seconds.

as I can tell the fuel line goes to the top carb first and then T's to the second and then third carbs. I was thinking if the fuel supply was not great enough the top carb was using all the fuel and starving the second two. with a few pumps of the bulb, it would supply enough for all three momentarily, and then back to starving them once they used the fuel. sound reasonable?

 

[Mi duckdown]

Re: mercury 90 fuel issue?

There should be NO LEAKS in fuel line whatsoever. Fix that leak first.

 

[Lone Duck]

Re: mercury 90 fuel issue?

Lone Duck: on board tank, vent is clear. I was wondering about the bulb as it will drip a little while priming as it begins to get firm.
Carholme: plumbing leak was through hull fittings as well as the "nipples" on the bilge pump and the live well pump. I did pump the bulb while running and it seemed to help, sometimes a little, sometimes enough to make it run fine for maybe 15 to 30 seconds.

as I can tell the fuel line goes to the top carb first and then T's to the second and then third carbs. I was thinking if the fuel supply was not great enough the top carb was using all the fuel and starving the second two. with a few pumps of the bulb, it would supply enough for all three momentarily, and then back to starving them once they used the fuel. sound reasonable?

Replace fuel bulb with a good one not a cheap piece of crap. Make sure all connections from fuel pump to carbs are good. Then fire it up and let us know how it goes.

 

[jdhgcb]

Re: mercury 90 fuel issue?

10-4 on replacing bulb and lines from tank to motor, and checking lines from pump to carbs. hopefully this will remedy the problem. I know sometimes it's the simple things that bite you. thanks for the help and I will post after these fixes and a trial run.

 

[MH Hawker]

Re: mercury 90 fuel issue?

any fuel drips means it will drip when it inst running and suck air when it is.