I'm having issues with this outboard. It's a 1988 2 stroke 9.9 Mercury. The problem seems to be that it is starving for gas. My setup is as follows.
1. Fuel line comes from the tank into a fuel manifold where I can switch tanks.
2. Goes to the primer bulb
3. Through the fuel line to a clear replaceable fuel filter.
4. Through the fuel line to the inline fuel filter under the cowling
5. Into the carb.

Sometimes I can get a hard primer bulb, sometimes not. I have noticed that after I get it running, I am not pulling gas through the line, at least not much. I can see that through the clear fuel filter. I have also noticed that if I pump the clear filter down with the bulb, when I stop, the gas is siphoning back down from the motor and refilling the clear fuel filter. This one has me stumped. It seems like I have an air leak in the line someplace but I can't figure this one out. All fuel lines have been replaced, all new hose clamps, new filters, I've tried a couple different primer bulbs, I have rebuilt the carb and replaced the O-ring and filter for the inline filter under the cowling. All of this has not solved the problem, and the motor is acting the exact same way as before I replaced everything. The motor will run for awhile but not really pull any gas. This motor DOES NOT have a fuel pump. Anyone ever have this problem?

Could it have water or moisture in the screen on the filter at the engine?

I have a 1996 Merc 8 h.p. that had similar problems.

replaced all the fuel lines between tank & motor with all new hose,
fuel bulb, hose clamps & plug ends that plug into the motor & tank.

Outboard tech suspected air leak in these and said often new replacement parts
have very poor quality right out of the box/off the shelf.

motor ran fine at idle but when you took off and put a load on the engine
it would bog down & act fuel starved.

New plug ends were defective, and when replaced, the fuel starvation
& air leak was solved.

w

Have you tried it hooked direct to the tank? and is the primer bulb arrow going in the right direction?

Doesn’t that model have the flat fuel pump/diphram on it?

Osky

Sounds like an air leak. Worked on small 2 stroke Merks back in my GW days.

No

I could change plugs. I might as well at this point but that should have nothing to do with it not pulling fuel.

Bulb is the correct direction and I have gone directly to the tank and even bypassed the filter under the cowing.

To my knowledge, it has no fuel pump unless it is integral to the carb.

Air vent on top of tank open?If not,,it wont suck fuel.

Yep. By the way, this is my kicker. My Evinrude 90HP runs like a Swiss watch off the same tanks.

Do you have a spare outboard tank laying around?Just for giggles,,I would try to run it off a different tank and see what happens.

Once had a fuel pickup line break inside a tank. Engine would idle. Upon acceleration the fuel pocketed in the rear of the tank and the pickup tube sucked air. Once the boat leveled at idle, the engine ran just fine. Check your pickup inside the tank.

should be on the back of the motor

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Yeah, it's got a fuel pump. Usually, those little Merc fuel pumps are pretty trouble free. You can get in there and trace it out. It's inline after the gas connection fitting on the motor and before the carburetor. Three ports, in, out, and vacuum. It will either have a vacumn line going to the block or be bolted directly to a port on the block to get it's suction.
I would buy or borrow a regular 6' Merc gas line that you know is good and bypass all those fittings, valve and filters, run it, and see if that cures your problems. Then go from there. A small pin hole is enough for them to be able to suck air.

THERE IS NO FUEL PUMP. Unless it is integral to the carb.

Had a fuel pump go out on me once. In a river that was up. Paddled to the bank and tied up. Took the lines off the pump and guts out of a ball point pen. Little trimming with my pocket knife and used the pen barrel and clamps to splice the line together. Made it back to my pickup by continually pumping the bulb. Luckily it was an outboard with a tiller.

I wonder if there could be a vacuum line on the carb that is sucking air? Gas should not be siphoning back down the fuel line once the motor is off. It should be staying in the system.

This picture is where the fuel line connects to the carb. The only thing behind this point is a filter and the quick disconnect. If you see a fuel pump in this picture please tell me.