At 5000 RPM, I should think you will burn a lot more than 1 GPH. You might get 1 GPH at 3000 RPM.

My 135 HP 4-stroke I/O burned about 5 GPH at 3800 RPM. Not sure how well you can compare I/O prop vs. OB jet, but I'm guessing that considering the HP alone would be somewhat valid. On that basis, I would estimate that you will burn 2 GPH at 4000 RPM, and 3-4 GPH at 5000 RPM.

I'm sure someone out there has real-world experience with a rig more similar to yours, though.

Regards.

Finegrain
Woodinville
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Regards.

Finegrain
Woodinville