my engine was carboned up and the tech told me i wasn't running it hard enough. it's a f 200 in line yamaha. out of curiosity, i called yamaha tech services and they told me the same thing. i'm running a 20p 3 blade prop and getting around 52 to 5300 rpm wot. he said i should be getting 6000 rpm at wot and that i was over propped. i have a 20p 4 blade that will rev up a little higher, guess i'll switch props. what do you cruise at?

I run 6000 all the time on my old Merc Black Max 150, still all original after 36 years! It hates cruising under 5700 rpm.

4500 FX21 250SHO
But make sure you run it WOT for a mile or more sometime during the day!

5200

My Merc EFI 150 2.5L redlines at 5600. Seems my motor has a sweet spot right about 4800 to 5200 where it runs the smoothest. I do know that extended idle like trolling and running structure scan will eventually foul the plugs. 2 stroke motors like to be run hard but not over the limits.
The faster you can run it without over heating and dropping water pressure the better it will be is what I am told.

You can run it as slow and easy as you want. Just blow it out good (wot) every so often. I never ran my boats hard. I like to cruise 45 mph or so. But the boat will tell you it's sweet spot. I always take it to wot before heading to the ramp. I never had a fouling issue.

About 6K

The motor should be propped to run the max rpm for that motor at WOT, then run it WOT fairly often to clean out the carbon. Its also a good idea to run Ring Free or Seafoam at least every other tank no matter how old the motor is.

5000 TO 5400 with my v175

I never paid any attention to it. I guesstimate maybe 3000-3500? Being a pokey old faht, as soon as I get on plane I throttle down to just stay on plane.

Yamaha HPDI 250, 25T 1, around 4000 after getting to first spot at WOT, Also WOT to ramp at day's end.
Tournament day WOT all day. FYI 65-69 mph at 5000-5200rpm which according to YAMAHA is within
its recommended 45-5500 WOT RPM chart. Hopefully you'll solve your problem, with the input on this site
I'm sure you will.

well, i got the boat back today and put my 4 blade 20p prop on. took it out for a run and the best ratio i could get at WOT was 5100 rpm and 48 mph. will try again tomorrow with the 3 blade 20p prop.

I'm thinking a 17p may be better, there is about 200 rpm per inch of pitch difference. If you were closer I have a 17p Vengeance for sale that you could try.

thanks. i've got a 3/18p quicksilver that needs a new hub and a yamaha spline. i'll get er done and see how that works.

ran my 3/20p today. 5200/51mph.