Adjust A Thrust

Adam,

Did you get your unit from Rex? What length shuttle do you have, and what is your screw setting? If you are using the 3.5' and dont have the screw open very far, you may need a 3.25' shuttle, let me know. You are only going to get so much more top end, as the GP has a lot of wetted surface, but installing a lighter prop, or boring the nozzle will increase the low end and midrange performance without losing the .5 to 1.0 that you gained.

Bruce Wolford Wet Wolf Tech

I have experimented with different length cones in the pump of my GP1200 and found the engine to be very sensitive to the extra load applied . Losses in Rpm of 100 -300 rpms are typical , yes a slight gain in speed 0.5 -1mph can be had ,but I am concerned that the extra load will cause the engine to be more susceptable to detonation . I believe that the Adjust A Thrust may need to have a lower pitched impeller to work best , anyone else have an opinion on this?

It's called a bored nozzle, but I'm sure Bruce can clarify.