What is usually the best rpm range for mileage. Set up is a tr21 with a yamaha 225 ox66 efi.

I have a 19' Astro(yes it's old) with a carburated Merc 150. When I Bought the boat I had read a test run that said best economy was at 4400 rpms. Since I have read several other performance reports on other boats that also indicated in the mid 4000 rpm range.

I can't recall if any of those reports were for 225hp or fuel injected.

I run a carb'd merc to. Best 4400-4600.

the best milage for any boat and motor is up to you you can tell where the sweet spot is on your motor when everything runs smooth

Both of my boats make a sucking sound and it doesn't make no difference how many rpms you run them at. I don't worry about the gas as much as I do the oil. My optimax oil is running around $45.00 a gallon. And that's the only oil Merc recommends for my motor due to the warranty.

If you read the on the water test on most outboard manufacturer's websites, you you will see it's usually around 3500 rpm.

Champion 206 Opti 225@ 4000 rps gives me the best gallon per hour according to my smart craft gauge.