[gilligan56]

Does anyone know if a pump filter on a 250 Yam ox66 vst unit would slow down the rpm's ? I throttled back in case of lean burn and figured like my diesels with a clogged filter tend to reduce rpm's.I replaced the main 10 micron screw on filters in the boat and wonder if I should go further. I have not tested the new filters yet but will go into the vst if needed.thanks

[cousinabe]

is the motor going into reduction mode? is it shaking? any gauge warnings?

if not, could be fuel system related.
low pressure pumps, dirty vst filter, clogged up pressure regulator screen or fuel injector screens.

[gilligan56]

no alarms just starts to slow down at high throttle settings above 3800 rpm. My guess was the electric fuel pump screen picking up water/aluminium crud and then not delivering full flow to the throttle bodies.