ox 66 low pressure fuel pump.

[scofflaw]

Not sure what caused the piston damage on my old motor. Chunk missing right above the top ring end gap next to cylinder wall. No carbon, no sign of lean burn, plug looked color perfect. Low pressure pumps were old

Sure don't need the same thing happening to my new used sx225txrz.
Runs perfect now, but is it possible for a failing LP pump to ruin a motor ?

[boscoe99]

Yes. The Perfect Storm can arise and cause harm to a motor.

LP pumps keep the VST tank full. Or should. If the LP pumps fail to adequately do their job a lean condition could exist in an injector. VST pump is starved for fuel and an injector can't supply the normal amount of gasoline.

Let's say one injector is just a tad clogged. Let's say the motor runs a tad hotter on the cylinder with the injector that is clogged just a tad. Let's say there is some carbon build up within the cylinder with partially clogged injector that is running just a tad hotter, which raises the compression ratio of that cylinder or causes bit of carbon to glow from being over heated. Let's say the gasoline is a bit degraded. It is more prone to detonation.

Bam. Bad stuff all comes together to destroy a cylinder. It can happen faster than a knock sensor can react to it. First comes the knock and then comes the CDI trying to counter it. The first knock can do the damage.

You can go over the Bass Boats Central Yamaha forum and read all about folks having replaced their mechanical lift pumps with an electric fuel pump.

[boscoe99]

How about some photos of the damage?

[scofflaw]

junkman took the block away, no photos. So you got 3 lp's feeding the vst. A single HP pump feeding the injectors, Owners manual doesn't say anything about replacing them just for the hell of it. What's the maintenance proceedure for these lp pumps?