2000 OX66 200HP Surges and Dies at WOT

[Bobs Maverick]

When WOT, motor dies like it is starving for fuel. If I leave throttle open when it dies, sometimes it will try to pick back up. Motor does not shut down all the time. If I put motor in nuetral, It usually keeps running but there are times when it shuts down completely. After shut down, motor starts perfectly. Motor will also surge approx. 300-500 rpm while running at speed. The first time this happened I was running about 5200 rpm and when it shut down if felt like I hit bottom. Any ideas ?????

 

[rodbolt]

Re: 2000 OX66 200HP Surges and Dies at WOT

sounds like the fuel rail is running out of pressure, keep doing it and you will fix the fuel system when replacing pistons.
when was the last VST service? last fuel pump replacements and last fuel system vacum test at WOT ?
wanna guess what lubricates and cools the crank and rod bearings as well as the pistons ?
research "lean piston failure two stroke" on the ole google.

 

[randy_252]

Re: 2000 OX66 200HP Surges and Dies at WOT

Couple of things you may check,

1. try pumping your fuel bulb to see if it will tighten up. If it doesn't go to 2. your fuel hose. replace if old and cracked. Tighten fittings on the hose,

2. hold that fuel bulb with the arrow pointing to the sky and pump. It should become very stiff, if it doesn't your floats in the carb are not seating.

 

[Bobs Maverick]

Re: 2000 OX66 200HP Surges and Dies at WOT

Thank you very much for the info. I will contact my mechanic in the morning and will not use the boat until the work you suggested is completed. Thanks again. Bob

 

[Bobs Maverick]

Re: 2000 OX66 200HP Surges and Dies at WOT

sounds like the fuel rail is running out of pressure, keep doing it and you will fix the fuel system when replacing pistons.
when was the last VST service? last fuel pump replacements and last fuel system vacum test at WOT ?
wanna guess what lubricates and cools the crank and rod bearings as well as the pistons ?
research "lean piston failure two stroke" on the ole google.

 

[Bobs Maverick]

Re: 2000 OX66 200HP Surges and Dies at WOT

I have had the boat and motor for about 1 year. Before using the motor I had an Annual Engine Service performed which did not appear to include any of your recomendations. In Feb. this year I had lower unit upper driveshaft searls and water pump changed. They did a pressure test and held 14.2 fine. Pull 02 sensor and clean, also did a decarb on engine and changed out carboned up plugs... replaced fuel paper filter on engine. Replaced battery and water pump impellar 1 month ago.

Also, I would like to add that the last time the boat was out (2 days ago) while in the slow speed zone I was running about 1300 rpm when the motor again slowed and stalled. It did this two times before I got to the ramp. Each time it started perfectly as if nothing happened.

I don't know if any of this information will help determine what the problem is but I do look forward to any further information you are willing to provide. Thank you again, Bob

 

[rodbolt]

Re: 2000 OX66 200HP Surges and Dies at WOT

if the fuel rail pressure rises above 35PSI the engine starts running very rich, if it drops below 35 PSI due to low VST fuel level it starts running lean, the ECU is quite stupid and assumes a rail pressure of 35PSI plus or minus about 2 PSI. your symptoms indicate low rail pressure for some reason.
there are a few other causes but lets make sure the fuel system is operating as designed before it causes a mechanical failure.

 

[Bobs Maverick]

Re: 2000 OX66 200HP Surges and Dies at WOT

Thanks again .... I will contact my mechanic this morning and see what he has to say. Again, I would like to say thanks for all your help and will reply as soon as we find something out. Bob

 

[Bobs Maverick]

Re: 2000 OX66 200HP Surges and Dies at WOT

Rodbolt,

Here is the latest on my motor.

1. Pull and check fuel pumps. Top and middle had bad diaphragm. Remove and replace 3 diaphragms and 3 gaskets.
2. Pull and check VST bowl, clean filter, replace bowl o-ring
3. Replace motor fuel filter and plugs.
4. Check and adjust T.P.S. (??????)
5. Check spark plug boots
6. Start and run
7. Check O2 sensor. No fluxuation after warmed up. Pull and clean, replace gasket and test again. O2 bad. Replace sensor and test. O2 okay
8. Check fuel PSI - good
9. Vacuum - okay

Total bill $800.00 .....

Will test boat in the morning and let you know if it is fixed. Just thought I would give you an update since you have been so helpful. Thanks again. Comments ?????


Thanks,

Bob

 

[rodbolt]

Re: 2000 OX66 200HP Surges and Dies at WOT

sounds like the fuel system is tuned up. time for a retest.