2000 150 OX66 power loss

[floridaflatbed]

when I first run my engine, it operates fine.
After a few minutes, it has a loss of power.
I ran fuel from an external tank to rule out fuel/tank/filter issues.
I cleaned the engine mounted fuel filter.
It act as if it is being starved for fuel.
Surging and dropping RPMs.
It operates to 1300 RPMs fine. Idles fine.

Could it be a waterpump maybe not cooling properly, and causing the engine to operate in a "safe" mode??

[Ken]

florida',
I believe there are at least two fuel pumps feeding the injector pump (it is fuel injected, right?) - I'm thinking one of those pumps is faulty. There is a way to test those pumps - you need a Yamaha service manual for the procedure.
Also, I believe your motor has an O2 sensor that needs to be cleaned on a routine basis. Again, the manual will describe the procedure, or maybe someone will chime in here and explain it - I've never done it.
I don't think your motor is going into "rpm reduction" mode from overheating. Do you see any signs of overheat? Any alarms going off?
Your alarm could be faulty.
In "rpm reduction" mode, the motor will shake violently from loss of spark from the ignition control. Rpm will cut back to about 1000 or less - is this what you are experiencing?
Ken K [img]smile.gif[/img]

[kingfish]

We had something that may have been similar with our 2001 OX66 225, and it turned out to be a hole in the diaphragm on the high pressure fuel pump. The local (remote Canadian) marina had just picked up Yamaha (we bought the boat/motor combo in the states and took it up there), and once they got on-line with Yamaha they got a definitive diagnostic procedure and ordered the part. One thing that was really striking about the performance in our case, besides the similarities to those things described here, was an absolutely incredibly high fuel usage. Like 5 times normal!

[floridaflatbed]

Thanks Ken.
The engine doesnt shake violently, just surges.
If I turn it off for a few minutes, it will run fine for a few minutes, and then right back surging again.

Thanks.
I think Ill try cleaning the o2 sensor, and then the diaphram


Thanks!

[floridaflatbed]

cleaned the o2 sensor, no improvement.
Going to change the 2 fuel pumps/diaphrams tomorrow.

[jb123]

you really need to TEST them as one could easily be bad. as for the pumps,if you can blow up thru them and NOT(NONE) down they SHOULD be ok, but 5-6 yrs should be replaced anyway as a general preventative, i have 00`s and havent had to yet.they are the primary pumps which feed the vapor tank and secondary hp pump. i would suggest pulling the vapor tank, you will need 2 crimp clamps, 1 tank o-ring. there is a filter inside that needs to be cleaned, use a general carb cleaner and after, ensure you prime up motor filter AND enough to fill vapor tank.when is the last time you changed the motor filter cartridge?if your primarys are bad you will see unspent fuel out the exhaust ports.even easier, drain the vapor tank and check for any improvement.

[floridaflatbed]

replaced the Pumps, problem still there.
What seems like a surge, is actually a DROP in RPMs.

Fuel pressure is 38 lbs, but drops dramatically during surging.

the rubber hose coming from the diaphrams jolts as if it has air pockets when the drop in RPMs occurs..

Checked for leaks....none.

cleaned the filter attached to the electric pump. there was some silt there. but still the problem persists.

I have an appt with the Yamaha dr on thursday.

Im just going to bring her in. Running out of time/patience.


....seems like it is improving though. I feel as if im getting close.

[jb123]

did you ever check the voltage getting to your motor as the efi`s are very dependent on that.

[boats.net]

If the fuel pressure is dropping then the elect fuel pump needs to cleaned or replaced, VST tank cleaned, fuel pressure regulator checked and screen cleaned and high pressure fuel filter replaced.

[floridaflatbed]

Well, I did the seafoam trick, Cleaned the VST tank/screen, It seemed to still be doing it slightly on the hose, but I needed a new VST tank gasket anyway, so I brought it in the the Yammie doctor.


He replaced the engine mounted fuel filter, and replaced the rubber gasket on the VST tank.

He also replaced the plugs again, they were black from carbon, and may have fouled after the de-carbonization process.


He said it is fine on the hose....I will water test it this evening.

[floridaflatbed]

Well we went out this weekend, the boat ran great.
I would have to contribute the cause to dirt in the fuel system.
Mainly, the screen in the VST tank.

I beleive it got there over time, due to a small tear in the engine mounted fuel filter.

The plugs were very carbonated due to the seafoam trick too.

Thanks for any help I recieved.
Hope this post can help someone else save some $$.

[jb123]

i do mine once a year as if your VP filter clogs, your HP pump will burn up,ching ching $700....glad to hear it is resolved.

[Hamfisted]

Yes, and make sure you have a Racor fuel/water separator filter installed in your fuel line prior to the motor. They prevent 99% of these problems.


Mike

[Olsinvest]

Bring this back to life (I hope). I have very similar issues. What is a "VST" tank and where is the engine mounted fuel filter located?

[99yam40]

old dead thread,
best to start a new thread of you own with all of your information