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1997 Mercury 9.9 HP fourstroke won't stay running

T

thebubba

Regular Contributor
I just acquired a 1997 Mercury Fourstroke Electric Start 9.9 HP outboard. I want to use it as a trolling motor on my 19' Lund Boat. Initially I tried to start it and it would not start at all. I cleaned the carb out as it had water in it somehow. It would start up and run for 5 seconds and then die. I pulled the carb again and found deposits so I had it ultrasonic cleaned so it looks brand new. Now when I try to start it I can only get it to start and run at a very low idle for about 5-6 seconds and then it dies. It is the Yamaha Powerhead version of Mercury Fourstroke motors. What am I missing here. When it does run it seems like it will be very smooth, I just can't get it to keep running or even start at a higher RPM.
 
What's the fuel pump look like - you might be "pumping enough gas" into the carb with the fuel line to get it to initially fire, but then it's running out of gas because the fuel pump is not pumping.

That would be my "first guess".
 
Graham,

Thank you for your suggestion, I think I just figured the problem out last night. This is a yamaha powerhead with their carb and it has a lot more parts and components than I am used to working on with other Mercury motors. After taking apart the carb for the third time, I discovered that I completely missed the idle jet, which is under a plastic plug inside the bowl area. I thought it was one of those permanent plugs that you have to drill out or something, but it pops right out and has an o-ring holding it in place. The only way I found it was closely looking at the parts diagram. This jet was completely clogged. Everything else looked perfect on the carb, but I double checked it all anyway. I think the reason it would start and run for a few seconds was the accelerator pump on the bottom would push a little squirt of fuel into it when I moved the throttle. I will try to fire it up this weekend and let you know. I can't believe I missed something so simple. I guess I always have more to learn.
 
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Re: 1996 Mercury 9.9 HP fourstroke won't stay running

I have a 1996 9.9 mercury kicker motor 4 stroke that will run for about 2 minutes and then die. I am thinking a weak fuel pump. When i disconnect the hose to the carb. It was spirting gas. I was looki g for a replacement fuel pump. But every where i look it says the part is unavalible. Part number 825470t. Anyone have suggestions. Thanks mike
 
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