I hate 4 Strokes

[bullie]

quote PM T2:

I fail to understand why the Moderators allow the discussion of Nissan outboards on this site.

Bestd,
PM T2

We can pull it off if it makes you too queasy.

[bullie]

I replaced the slow speed jet in the original carb to get it running at the beginning of this fiasco. It was clogged and I could not get a wire to pass through it. The holes are quite tiny. It is interesting that a wire would not pass through the new jet either. It would stop halfway from either direction though I can see a tiny spot of light looking in it.

The motor is the same as a 2007 Mercury 9.9 I had. I think the model numbers span several years.

[outbdnut2]

I don’t like 4-strokes because, except for a select few, as they get above 20 HP, they are so darn heavy! Most models are at least 100 pounds heavier than the same HP 2-stroke.
Dave

[slim60]

The last time I changed the strings on my acoustic guitar I cut the ends off the old strings. Most cut them off after they are installed but I did’nt that time. They make great carb cleaners. After a 24 hour soak in NAPA carb cleaner and compressed air of course. Then another spray with aerosol carb cleaner. They last one I did was a MTD rototiller 4 stroke that was under a lean to for 10 years.

[wedgie]

I’m interested to know the answer to this problem, as it could potentially apply to one of my old Lauson 4 strokes. Why set such strict limits on what is open for discussion ?

[billw]

This is all I could come up with. I don’t know if it has anything to do with your problem or not. Where I work, I can count on one hand the engines we service that are under 10 hp. Most are 150 hp and up.

Situation
Mercury Marine has identified a performance issue with the fuel pump on the above listed outboards. The check valve seat
located within the fuel pump could cause the performance of the fuel pump to diminish as the engine run time increases. It has
been determined that all fuel pumps within the specified range should be replaced.
Fuel pumps that have been reworked at the factory will have a green paint dot on them. If your fuel pump does not have a
green dot located on the fuel pump body, proceed to the correction procedure.

Long live American manufacturing!

[joesnuffy]

"It ran for a couple weeks and then quit. I cleaned the carb over and over thinking it was a fuel issue. I gave up and put on a new carb this morning. Still the same thing. It will not start unless the throttle is advanced and then will only run if the choke is engaged. It will die if I attempt to throttle down or if I disengage the choke"

I had a 40hp Yamaha that I rebuilt the engine and it ran well for about 2 weeks although it was a 2 stroke it was doing the same thing yours is. I would have to run it with the choke partially on and run the throttle up a bit and it would not get up to wide open throttle. It had 2 carbs I must have cleaned them 4 times still wouldn’t run right. It ended up being a sheered flywheel key and the flywheel was about 180 degrees off but since BOTH spark plugs fire at the same time which is called "wasted spark" because even though the piston is at the bottom of its cycle it fires. This allowed the engine to run but just not correctly. I would check your flywheel key for being sheered just to rule it out I would bet you have a wasted spark CD type ignition. It was amazing it did run and it could at least get you back to dock worst case so I never thought about a sheered flywheel key.

I hope this helps I pulled my hair out finding the problem,

I would like to also thank Fleetwin he helped me to finally figure it out.

Joe

[bullie]

quote BillW:

This is all I could come up with. I don’t know if it has anything to do with your problem or not. Where I work, I can count on one hand the engines we service that are under 10 hp. Most are 150 hp and up.

Situation
Mercury Marine has identified a performance issue with the fuel pump on the above listed outboards. The check valve seat
located within the fuel pump could cause the performance of the fuel pump to diminish as the engine run time increases. It has
been determined that all fuel pumps within the specified range should be replaced.
Fuel pumps that have been reworked at the factory will have a green paint dot on them. If your fuel pump does not have a
green dot located on the fuel pump body, proceed to the correction procedure.

The 1st thing I had to do with this motor was replace the fuel pump. I assume it is of recent manufacture.

[joesnuffy]

I’ve got a clear fuel line on my test tank and can see the fuel getting drawn or not getting drawn. On a small engine like yours less fuel would need to be drawn on a 150hp it would need much more. I normally just pump the fuel bulb a bit to see if carb is staying full of fuel if I think fuel pump might be an issue or just disconnect the out fuel line of fuel pump and crank engine over a few pulls to see if fuel comes out. I would say you have an ignition problem since you have gone through the fuel system and I assume you have good compression on both cylinders. I would at least check your flywheel key even though its a four stroke it can run with a sheered key or partially sheered key etc. I put my engine on TDC and put a pencil in the spark plug hole and the #1 piston was close to the bottom of its stroke not the top of stroke but I had to pull the flywheel to actually look. But it was a great feeling knowing that it was most likely my issue. That engine could have had a sheered key many years and it would run but just not like it should and the flywheel may have shifted again and that could be your issue. I hope this helps but on my Yamaha golf cart and another buddies Yamaha 4 stroke it turned out to be ignition problem not a carb probelm when I was getting them to run correctly.

Hope that helps,
Joe

[fleetwin]

All I can say is that it seems like this engine has some sort of original defect that never got resolved. In these cases, we must make no assumptions, and remember to pay close attention to "the basics". I keep hearing references to the flywheel key, just seems like a sheared key would definitely affect valve and ignition timing. It is surely worth spending an hour or so checking timing belt orientation and the flywheel/key. How about the cam gear, perhaps it is improperly oriented on the camshaft/sheared key as well.
Again, you mentioned the engine ran for a few weeks, but how well did it run? Was it still tough to start? Did it idle properly?
You replaced the fuel pump and carb with new OEM items, correct? Did the engine run better/differently when these components were changed, even just briefly? Everyone has spoken about the small passages in these carbs, perhaps a dirty fuel supply has messed up this brand new carb….Doesn’t seem likely, but anything IS possible.
Try to avoid the temptation to "dig too deep", 95% of our engine problems are related to very basic issues. Trust me, I am not preaching, just trying to help you avoid the traps we all/me included create for ourselves…
This is an interesting project, wish I had more knowledge about these engines.. Look forward to finding the basic issue and getting it resolved.

[Author]

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