2001 YAMAHA 200 OX66 flooding issues needs full throttle to start

[jstatham]

I am copying my post from iboats. Hopefully I can get some help here.

Hello everyone I purchased this boat about 2 years ago and the motor has ran like a top until this past weekend. It started with not wanting to crank unless it has almost full throttle. This is a fuel injected motor and never needed more than just pressing the choke to get it started on a cold start. Today I gave it a basic tune up. New Plugs, Impeller, also ran injector cleaner through the motor with a little less than a gallon of gas. While running the cleaner through the system I noticed tons of fuel coming from the prop area. It went through the entire gallon of gas in under 2 minutes. I checked the fuel pressure and it was 35 psi on idle. If I turn the motor off and pump the bulb gas starts leaking from the exhaust,prop area and I have to give it full throttle to get it started. It is almost like something is stuck open and pouring gas into the cylinders. I took the breather off and pumped the bulb and from what I could tell all the throttle bodies looked the same and no injectors were leaking and I could not tell where the gas is coming from. I am leaning towards the lower pressure pump but really not sure what to troubleshoot next. Any help will be greatly appreciated.

Yesterday I took off the high pressure pump and split the fuel vapor separator and everything seemed to check out fine. The float is working properly so the only way for I see for the fuel to get into the motor is from a stuck open injector. What the best way to tell which injector is the problem? I also see online where people talk about the 2 low pressure pumps torn diaphragms causing issue with flooding but by looking at the diagram i see no way for it to get into the motor except through the injectors? Any help will be greatly appreciated.

[mn808gade]

the lift pumps are mounted on the block and are activated by pistonrodcrank..pull them off and dollars to doughnuts you'll find plastic diaphrams with little tabs sticking out over top of f/pumps..i have a hole stack of em,(cracked).i stock three sets of them,thats 9 pumps total,carbed and efi's use 3/motor,and hpdi's use 2/motor... new pumps and repair kits are furnished with black diaphrams-th

[RSWORDS]

Yep, I'd put money in busted dia in the L.P. pump. You can listen the two 10mm mounting bolts and pump the primer. You will see gas coming out the hole that gets crankcase pressure.

[cali kid]

Yep, I'd put money in busted dia in the L.P. pump. You can listen the two 10mm mounting bolts and pump the primer. You will see gas coming out the hole that gets crankcase pressure.

+3 on the lift pump.

[Bullet 20cc]

+4

Those lps always give symptoms when they start to go but not always the same symptoms. They don't always bust/tear but they do get so old, brittle and worn out that they don't function properly which will give you the exact same symptom you are having. That is always the very first place to start with a fuel issue on these motors. The lps are incredibly easy to service anyways...you were already half way there if you had vst can off already. Some prefer to buy all new pumps for $40 x 3 but I prefer to break em apart and change the 2 diaphragms and 2 gaskets in each one for $12 x 3 instead. I always keep 3 rebuild kits on hand. Just make sure you get the diaphragms/gaskets stacked in the right order cuz they are stacked differently on either side of the pump body. Also take them apart slowly so you don't lose the spring and cap that you will have to reuse. $36 and 30 minutes of your time and it will run just like new again...or $120 and 15 minutes of your time if you decide to go with all new pumps instead. You should also pick up 3 pump to block gaskets too just in case but usually you can reuse the same ones over again as long as they didn't split when removing the pumps...which rarely happens.

Definitely run a 10 micron fuel filter/water separator right off the fuel tank for this motor which will save you any headaches related to the rest of the fuel system (vst filter, fuel filter on block, injectors) in the future.

Those motors are arguably the most dependable V6 2 strokes ever made and very easy to service yourself. Capable of big power too!

One other thing...being a fuel injected motor there is no choke on this motor. Pushing the key in does absolutely nothing other than exercise your finger muscles. Just turn the key and go...no matter how cold the motor is. That key push feature is only there for carbureted motors.

[jstatham]

Thanks everyone. This weekend I installed 2 new low pressure pumps (the 200 hp only has 2). The top one was leaking. I also put in new plugs,new impeller,cleaned the 02 sensor, and cleaned high pressure tank filter and she fired up and ran like a champ. Thanks for all the help. I now just need more time to hit the lake. I am going to get the 10 micron fuel water separator filter as well as rebuild both old pumps and have them on the boat just in case. I love this motor and how is sounds and run.

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[jstatham]

Which fuel water separator do you recommend? Will this one work? https://www.amazon.com/gp/product/B0...A1M8164820ME2R

[Bullet 20cc]

Congrats on getting her purring again...she sounds great! What I noticed about fuel filter/water separator shopping was that the cost of the system was related to what material the mounting bracket was made of. I saw choices of stainless steel, hard plastic and some other kind of synthetic material. I chose the stainless steel model for $66. The filter part and plastic bowl are pretty much the same on all of them and can even be replaced with whatever name brand filter you like. That one you listed does not have the bracket at all. It is not a complete system...it's only the replacement filter. Also they come with fittings made from different materials...brass, aluminum and even plastic I believe. I wouldn't go cheap on the initial purchase as that is pretty much the foundation of your filtration system. And a direct injected outboard (hpdi, optimax, etec) needs the best filtration possible (10 microns).

You love that motor and you very well should cuz it's one of the best ever made in my opinion...of course my opinion is biased cuz I'm a Yammie guy...

[jstatham]

Thanks. I already have a separator but I want to replace the filter with one with the clear bowl. With the one I posted work?

[Bullet 20cc]

Oh...my mistake on that. Yes it should work just fine as long as the filters are the exact same diameter and that one you listed is the standard size.