OX66 Oil Pump Operation?

[TomS]

Can anyone explain how the oil pump works on a Yamaha EFI outboard? Was looking at the shop manual this afternoon and trying to figure it out. Looks like there is a single feed to the pump from the engine mounted tank, it then gets split out into 6 separate lines leaving the pump, but then they are all combined again before going into the VST tank.

Why are there 6 separate lines? Any common failure modes or conditions to look for on the pump itself? You don't see it mentioned here very much other than adjusting the oil link rod.

Thanks,

-- Tom

 

[Ray Neudecker]

Re: OX66 Oil Pump Operation?

Six lines for six cylinders, since the Yamaha injects the oil into each cylinder seperately rather than mixing with the fuel forst. The pumps have been extremely reliable.

 

[JUSTINTIME]

Re: OX66 Oil Pump Operation?

very reliable
there are also check valves so the back pressure of motor does not blow oil back into the pump

 

[TomS]

Re: OX66 Oil Pump Operation?

In the service manual, it sure looks like there is a single line to the pump, then 6 lines out that meet up again in a row of connectors below the check valve, and then that single line feeds the VST. And speaking of that, isn't the VST where the fuel and oil get mixed, Ray?

Thanks for the help guys..

-- Tom

 

[JUSTINTIME]

Re: OX66 Oil Pump Operation?

no
oil is injected before the reeds
fuel comes atomized through the carbs which then hooks up with oil
the vst
vapor separator tank

 

[TomS]

Re: OX66 Oil Pump Operation?

But there aren't any carbs on EFI?

I'm pretty sure the VST is where the oil gets mixed with fuel before being pumped into the fuel injectors.

Are you guys sure you are talking about an EFI OX66 engine?

See pic below, it sure looks like 6 individual oil lines are coming out of the oil pump, then combined into a single feed at piece #10, then fed into the VST.

-- Tom

 

[JUSTINTIME]

Re: OX66 Oil Pump Operation?

i think oil would clog the injectors
i believe it is still injected before reeds

 

[bernieb]

Re: OX66 Oil Pump Operation?

I believe your right Tom, on the oil delivery, and for the purpose of the six oil lines in the middle ,so to speak , is a good question. My guess is as rpm goes up,it brings in another supply line for more oil .

 

[rodbolt]

Re: OX66 Oil Pump Operation?

on the OX 66 the oil is fed through a 6 into one manifold then through a check valve to the VST.
the system is still a variable ratio determined by the amount of travel of the oil pump arm