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2001 ox 66 low press fuel pump

crjron

crjron

New member
Is there any you tube videos or postings with pictures on how to replace these? I was thinking about just replacing the diaphragm's but replacing the pumps seems easier and the motor is 10 years old. Is there any got ya,s or is it pretty straight forward? I had a earlier post about the engine running fine then just stopping after 30 Min's after I had replaced a water/fuel filter. I put a new filter on again and a new fuel primer bulb but the bulb never really felt hard. We put a pressure Gage on it, and it points to the low pressure pump not pumping. I want to thank you to all of you that took time to answer my other post.

Thanks Rv.
 
It's easy to replace the diaphram.Easier but costlier to change the pump.
After a repair and it won't work??
You rebuild the whole pump?Or just the diaphram?Sure it's together right?
This might sound far fetched,you need to do a compression test to start the diagnosis.
The low pressure pump operates from the compression on one of the cylinders.
What motor?Hp?Serial#?
Some Yams have 3 low pressure pumps.J
 
It is a 2001 200HP ox66 (sx200TXRZ) It just hit 200 hours. I replaced the fuel bulb and fuel/water separator filter and it ran fine on a water hose. But the engine fuel filter does not stay full, goes down to about 1/4 inch above the screen. Fuel looks as if it only trickles in. Hose's are fine but the fuel bulb really never gets hard. I saw a post on another site and the mechanic said if the bulb does not get hard that this is due the low pressure pump not doing its job (holding pressure) to feed fuel to the VST pump and the motor will run fine for a little while and quit like you turned off the key. This is what my boat just started doing and also the other posters boats on the other website. I had to pump the bulb a few times to get back to the ramp. I checked the vst filter and pump, clean and working, also replaced engine fuel filter and o-rings. This is why I was asking about (difficulty) of replacing the low pressure pumps. Fuel system diagrams only shows 2 low pressure pumps for this engine. Thanks RV and if it fixes the problem or not I will definitely post. P.S. Pic shows were fuel is just above screen.
 

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If the fuel bulb never gets hard while you are squeezing it with the engine off , it means that the pump Diaphragm is Ruptured(assuming your fuel bulb is in proper working condition). When the pump ruptures the engine will run for a little while and stall. Replace both pumps. They are not expensive. I carry them in my service truck. Common problem.
 
Thanks, Chris, Not to hard to replace I hope? Why do they use zip ties instead of metal clamps on all of the hoses? Also I changed foot oil and it was clean but when I added the new oil I tried to purge most of the air out and oil came out of my prop hub. I guess I need to replace the gaskets or is this normal if a fool tries to over fill something?
Thanks again for all the help, having to do this on a budget, RV
 
When you fill the lower unit gear oil, you will remove both plugs (Upper and Lower) you will now fill the gear oil from the lower hole until it comes out of the upper hole. Once the oil comes from the upper hole stop pumping, insert the upper vent screw, disconnect your fill pump and insert the drain screw. Yamaha lower units will start to leak oil out of the shaft seal at about 10lbs of pressure in the case.
 
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