2003 Mercury 9.9 4 stroke (323 cc) bogging

[MarvinGabriel]

Ok, This is not a gas tank issue, so I thought it wise to start a new thread. so this engine is getting frustrating. I replaced the gas tank, the primer bulb/fuel line, and went ahead and put fresh fuel lines on (the old ones were mushy), and replaced the fuel filter.

Just to refresh, I was cruising along, and the engine started to run a bit slower, then just stopped! It would start for a second, then stop. So I just deployed my oars and rowed back to the dock. Today, I went to the local Mercury dealer and bought a new Mercury fuel hose, and gas tank. Added fresh gas, and started the engine. Idled fine, but I could not get it to leave idle. It just bogs, like it's starving for fuel. Runs a tad bit better at half choke. I pulled the plugs and inspected. Both have white electrodes, confirming a lean condition. I removed, disassembled and cleaned the carb. It wasn't a mess. Fairly clean, and I didn't see anything that would cause this issue. I think that the fact it runs better at half choke confirms a carb issue. SO, a couple of questions:

1. I've been rebuilding and cleaning carbs for 40 years. I used to drive carbureted cars, so had issues to deal with. I rode motorcycles, and once again, had to clean carbs. I live on a farm with a ton of carbureted small engines, and well...they need cleaned! Am I missing anything in the carb cleaning on these Mercurys?

2. That vacuum hose that comes from the air box, where does that go? A Vacuum Advance? I haven't seen one of those in a dog's age! I know the issue is enhanced when it's disconnected.

3. The engine doesn't idle right anymore. I tried adjusting the mixture, after cleaning, and it won't idle until about 4.5 turns out. And more turns out, it just doesn't change.

Well, I guess that's about it.

Thanks,
MG

 

[MarvinGabriel]

update: I removed the carburetor again, disassembled it, and put it in my Hornady Ultrasonic cleaner with the regular reloading brass cleaner. Ran it heated on the long cycle. I rinsed it all out with water, went through every passage on everything that looked like it moved gas, reassembled the carb, put it in the boat, and it started with the first pull. No more hesitation on acceleration, and it seems to run perfectly. I’m on Lake of the Ozarks so a Sunday afternoon romp is likely to be less than satisfying, so I’ll take it out tonight. I wonder what was gummed up? Everything seemed fine when I cleaned it before.

 

[MarvinGabriel]

Final update in this one: because this will be asked many times: yes, you can absolutely upgrade a 2002 Mercury 4 stroke 9.9 to 15hp with a carb swap. The displacement is 323cc on the 8, 9.9, and 15. The timing is the same, the exhaust is the same, but the carburetor has a bigger Venturi. Mine had the following results:

it’s on a 1985 Lowe Big Jon 1648, with two batteries, a trolling motor, basic bow fishing gear (no bowfishing deck), and 6 gallons of gas.

9.9 carb: top speed was 17.4 loaded like that, and just me driving. About 4,100 rpms

15hp carb: too speed was 21.2 and was able to max out the rpms at 5510, before I backed it down a bit on the throttle.

the upgrade was worth it for me. Super simple upgrade, and the carb was not all that expensive.