Yamaha OX66 flooding

[chbaker3]

Hey guys I have a 1999 225 OX66 that I am working on. The motor only runs at high idle (>1500 rpm) and is pushing to much fuel. The prop and grass around the motor is full of gas and oil.

Thus far, I have changed the O2 sensor (reads .8 volts), reset the TPS (.5 volts when throttle plate is completly closed) changes all fuel pumps (lift lumps and high pressure)and had all injectors cleaned and tested. The fuel pressure is 35 psi and cylinders all read 125.

Any other ideas? spark plugs are starting to get expensive. I do have another engine I could borrow parts from. I have used the injectors from it and it ran well unless you tried to get over 5000 rpms. As the engine is now, you cannot even get it into gear while in the water.

I do not know anything about the history of the motor. I got it in a non-running condition.

I am going to go get the injectors off the other motor and new spark plugs on Tuesday morning. If anyone has any ideas, I am more than happy to try those.

[Rich Z]

Typically it will idle high until it it’s fully warmed up. The ecu advances the timing when cold. If continues to idle high after warm up you should check the sync-n-link. It maybe because one or more butterflies aren’t lined up correctly or idle screw turned up too much. A lean condition will also make it idle high. You can also check the thermal sensor and air temp sensor.

[firefighter7302]

have u checked the linkage going to and the adjustment of the fuel oil mixture????

[chbaker3]

A little more.

I came to the conclusion about the pooling fuel in each cylinder by leaving the plugs loose for a few seconds while turning the engine over. This allowed black unburnt fuel to escape. Also if you look into the cylinders with a flashlight you can see pooling fuel. If you turn engine over without plugs it sprays liquid fuel, not vapors. While running it is constantly spraying unburnt fuel out of the exhaust hub. If you hold your hand there or a sheet of paper it is sprayed with black unburnt fuel.

I do not have a winky, but will be getting one soon.

As far as testing here is the history of my test. After rebuild, I was able to get engine started easily. On the hose it would idle great. I went put it in the water. Here, engine started well and put it into forward and reverse without too much problem. With this we decided to.launch.

I backed boat off of trailer and engine decided to kill. I thought maybe it was the fuel line. I went to the motor and pumped the bulb. I was able to get the engine started. I had trouble getting the engine to go into gear after this point. I got the boat back to the dock and disconnected the HP pump. After turning engine over for a few seconds and it would start and run for a few seconds. If i would hook pump back up it would do the same thing.

We winched the boat back on the trailer. The next day it would start on the trailer only under advanced throttle. I decided to go back to the launch and try a few things. I would start the engine under advanced throttle with the engine tilted up. I would then put it into gear and trim it back into the water. When the prop hit the water it died everytime. When I would trim it back up raw gas would drip out of the intakes.

I decided to bring it to the shop. I worked with them to test some things out. Nothing they did made a difference. They were mostly taking parts off a loaner motor and putting them on mine. After them doing this for a week I decided to pick it back up. There was no reason the pay them to swap parts when I could do that.

I decided to tear motor back down and recheck every line and port in the block. Everything was clear and put back together according to spec.

When I pick up the boat, I took some loaner parts with me. I changed the stator, trigger, flywheel and crank sensor. None of these made a difference. I decided to try the injectors and VST.

So I put the other set of injectors on the motor. It ran better. I put the boat in the water and tested the motor while on the trailer. It went into and out of gear well. Let it idle in gear for about 10 minutes before I decided to take it off the trailer.

Took it off and it still ran decent. I had to idle a little high, but i figured i fast starting to figure it out. I ran up the river a few miles. When I would try to punch the engine to get on plane it would bog down. If I backed off it would run fine. I thought maybe I had to much prop. So I worked it up the RPM range and it was fine untill I got to about 5000 (3/4 throttle). I was by myself so I could not pump bulb or do pressure test.

I made it back to launch and put it back on trailer. Here I decided to load test it again. Again it acted the same at about 3/4 throttle. I tried pumping the bulb but it did nothing. I did not have my fuel pressure gauge with me. After this i decided to send my injectors back off for testing (I had them tested and cleaned while doing rebuild.) I brought the other injectors back to shop.

When I got my injectors back they all test to spec. I put everything back together and went to the water. Motor acted the same. I retested the O2 and it was reading .1 volts but running rich. I figured maybe the O2 is saying lean so the computer is responding. I recleaned the O2 system and the same so I put a new one on.

With the new one it reads around .8. I rechecked the TPS and it was fine. I also rechecked all other sensors and they all tested well according to the Clymer manual.

Today I went get that other set of injectors again. Still running rich. (this is funny because they ran great 2 weeks ago.) I did do a peak voltage test one the coils and they all seemed fine.

Next time I have a chance I will test the Ohms of the boat and put a new battery in the boat to eliminate those problems.

I have checked the Oil Linkage and it was correct. All buterflies were synched and I have tried with them 100% closed and opened with the only difference of flooding more when closed.It will not come close to idle when they are closed.

[Charlie206]

Are the injector drivers separate of the ECU, or incorporated into it on that engine? Borrow the ECU and drivers if separate from the other engine you have and see if it makes any difference.

[201pro]

Have you checked/changed the 3 low pressure fuel pumps? When these pumps fail, they will leak fuel into the crankcase and could cause the excessive fueling. Also will give low fuel pressure/supply at full throttle and cause a low power situation.

[Rich Z]

Im with Charlie on this one. Get another ecu and see what happens.

[JUST-IN-TIME]

its your fuel LP pump or the vst needle is bad

[Rich Z]

Also, check the hp fuel pump in vst. It should be around 35-36 psi. If its any higher, the fuel pressure regulator is bad or the screen behind it is clogged.