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post #1 of 13 Old 10-12-2011 Thread Starter
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Yamaha outboard question

Just bought a boat equipped with a Yama 9.9 high thrust motor.

Before taking the boat out, I ran the motor whith the shaft in a bucket.
It started easy, than ran great. Ran it a few times for 15 minutes at a pop.

Took the boat out for the first sail, and:

A- it doen's start as easily.
Once it does start, I have to give it throttle to keep it from stalling

B-it has a surge at low speeds. It runs smoothly at half power and above, moving the boat at, or near, hull speed. When I let it try to idle, it surges and stalls. Even motoring at low speed, it surges.

motor surge - YouTube


Any thoughts?
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post #2 of 13 Old 10-12-2011
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Dirty Carb

I have 2 of these on my boat. Your vidio sounded very familiar.

I'm betting when you took it out you stired something up. Remove the carb, then the bowl, and spray out with carb cleaner. You most likely do not need any parts.

It's easier than it sounds:
- 2 10 mm bolts hold the carb to the manafold (top and bottom)
- 2 wires for the electric choke
- a plastic clip for the throttle linkage. Press down and in and it snaps off.
- fuel hose
- perhaps a crankcase vapor hose
- 4 screws to take the bowl off
-the main jet screws out easy. Idle jet often falls out in you hand when inverted.
- Float comes out by pushing the hinge pin through; a small nail should do. clean the needle valve.

Also, it sounds a bit lean. If there is a mixture screw, turn a half turn counter. However, most new engines don't have this. E-10 is the problem (it's a bit leaner).

Yup, I've done it once or twice.

Fuel pumps and filters are also problematical, but since it ran under load, not this time. Good spares to have, though, since they are really easy to replace.

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Last edited by pdqaltair; 10-12-2011 at 11:01 AM.
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post #3 of 13 Old 10-12-2011
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How old is the fuel? If the fuel has been around for awhile it would be a good idea to replace with new.
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post #4 of 13 Old 10-12-2011
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I fully concur with the cleaning. Check with local marinas to see if you can purchase non ethanol fuel. Airports that support general avaition also have non ethanol fuel. Using non ethanol fuel is worth the extra cost. Before it was available I was cleaning my carb about every 3 months. Since going back it's been over a year. I didn't even drain it last winter, started first try in the spring and has ran all summer. If all you can get has ethanol, use a good stabilizer, only buy enough for your immediate needs. If the motor is going to sit for more than a couple days run the fuel out of the carb. When you take it apart to clean it make sure you can get the drain screw out of the fuel bowl, about once a month rather than running it dry, drain it to remove any water/crud that may be taking residence. Don't let fuel sit in a storage can, if you buy more than you need, use it in your car and start fresh the next time you go sailing. The 9.9 probably has an external tank, a good course of action might be to drain it if the boat is going to sit for a week or longer and refill the next time you take the boat out. A couple gallons of 50:1 or even 16:1 isn't going to hurt your car.
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post #5 of 13 Old 10-13-2011 Thread Starter
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what about the choke?
It's an automatic choke. Not sure where this actually is, and how I might check it.
Any thoughts?
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post #6 of 13 Old 10-13-2011
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I know there used to be a way that folks "primed" their Yam's and that was by twisting the throttle hand fully open 4-5times before they started it. These are great little motors, but they've always had a tendency to be a little tough to "cold start".

However, I think you've also got to consider a full carb cleaning because of the other issue you mentioned; not-so-good idle. There's a low-speed jet, or any of them actually, that can pick up some very small debris in today's fuel and easily get clogged up. An annual carb cleaning isn't a bad idea to keep you motor trouble-free in the long haul. That and vigilant attention to the water flow, i.e. impellar change every 2 years at least.
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post #7 of 13 Old 10-13-2011
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Quote:
Originally Posted by emoney View Post
I know there used to be a way that folks "primed" their Yam's and that was by twisting the throttle hand fully open 4-5times before they started it. These are great little motors, but they've always had a tendency to be a little tough to "cold start".

However, I think you've also got to consider a full carb cleaning because of the other issue you mentioned; not-so-good idle. There's a low-speed jet, or any of them actually, that can pick up some very small debris in today's fuel and easily get clogged up. An annual carb cleaning isn't a bad idea to keep you motor trouble-free in the long haul. That and vigilant attention to the water flow, i.e. impeller change every 2 years at least.

Yes, I pump the throttle about 2-3 times. There is an accelerator pump.

The electric choke is the black thing setting on top of the carb (2 wires). I don't know of any good way to test it. I do know that they fail on occasion. However, at that point, it simple won't run at all, in my expereince.

Yeah, the water pump impellers do not hold up well. Not easy to remove the lower unit, but easy to replace the impeller after that.

(when asked how he reached the starting holds on a difficult rock climbing problem that clearly favored taller climbers - he was perhaps 5'5")

"Well, I just climb up to them."

by Joe Brown, English rock climber




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post #8 of 13 Old 10-13-2011
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Sounds like you have some blockage in your low speed idle circuit and as others have posted a good cleaning should fix it. I always use a Hypodermic needle filled with rubbing alcohol to ensure all the passages are clear prior to reassembly. Old gas will varnish the small passages and block them and even spraying carb cleaner will not always clear them….High pressure air will though. If the motor was run on gas with Ethanol…The Ethanol will eat fuel lines and the small pieces will/can clog up the carb. I use to earn side money rebuilding carbs that owners let sit all winter full of gas. Also, most electrical chokes…you can hear them click when you operate them.
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post #9 of 13 Old 10-14-2011 Thread Starter
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Great timing on the srynge suggestion.
I am a nurse.
I am at work.
Must be one of those things around here somewhere.
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post #10 of 13 Old 10-14-2011
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You might want to check the crankcase vapor hose for blockage. I had a yamaha 9.9 once that started up and ran well for a short time, then would stall out. You could keep it running by pumping the primer bulb. Turned out that the excess pressure caused by the hose blockage couteracted the fuel pump diaphragm. I removed the hose, cleared out the blockage, and the motor ran fine after that- mind you that was after a few days of taking the carb and fuel pump apart and cleaning them out- several times, replacing the strainer, checking the fuel inlet for vacuum leaks, trying different fuel tanks, and just generally being puzzled when none of that worked!

Anyway, it's worth a shot and easy to do.
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