2002 Yamaha 200 OX66 fluctuating throttle

Pound puppy

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Jul 19, 2014
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I've got a pesky problem that is really starting to tick me off. A few weeks ago I started having a throttle response issue where I would physically throttle up and the motor rpms would catch up to my chosen throttle position a few seconds later rather than instant response. My buddy who owns his own repair shop checked it out and found that I had a few injector O-rings that were cut so he replaced them but didn't have time to water test the boat so I told him I would over the weekend. Took it out and no improvement at all, actually noticed that it seemed a little worse now(can't go past 5100rpms where I use to hit 5900) whether or not it was from something he did or the problem was just worsening I don't know. But since I ran a heavy dose of seafoam through the fuel system(5gal can with 3 cans of seafoam straight to the motor bypassing the main fuel tank) which brought back my throttle response but still hasn't eliminated my fluctuation problem. I have taken the injectors out and had them serviced and found that all 6 had a flow rate of 100 but are now back up to 110 but that hasn't changed my fluctuating throttle. I have pulled the O2 sensor and the assembly and throughly cleaned everything back to almost brand new condition minus a few tiny spots and that hasn't changed anything either.

Today I pulled the LP's and tested them and found that one has a slight leak which I just order new LP's that will be here in a few hours but I am not certain that will eliminate my issue but we shall see. Any advice would be awesome!

I pulled my VST assembly apart, no debris in the tank and the filter was clean as a whistle and looks like it did a few months ago when it was put in. The fuel/water sep boat side was replaced at the same time as well as the primer bulb when the VST filter was done. I did purge the fuel system(valve on top of the VST tank) while it was running and it didn't have much of an effect unless I held it down for a few seconds and the engine would die off but would fire up instantly as i quickly turned the key. Normally I would test the fuel pressure but I can't find my adapter to connect it.

I normally run the boat for atleast 6 hours a week on avg without fail but for the past few months between having issues with it and being out of town for work and such I haven't had it out much which is killing me but I don't think this is a sitting issue for the boat. I am starting to go nuts with this and not having the right stuff to test different sensors its proving difficult.
 

Pound puppy

Cadet
Thread starter
Joined
Jul 19, 2014
Messages
17
When I say fluctuating I mean that when I throttle up to about 9-1000 it will hold at 900 for a few seconds and than will rise to about 1900-2900 on its own. I don't think it is a TPS problem only because of the change after the seafoam flush, but at this point I'm not ruling anything out
 
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