We were just up in Eagle River, WI. We always rent a 20 something tri-toon, had a 150 Merc this year, very nice ride. Pulled a 3 person tube & multiple skiers with no problem.
There were several toons there with 350's, one with a 400.
Is your son in Missoula? My brother is ~30 miles NE of...
Yeah, I was surprised by #s as well. I originally went by the conventional wisdom of 200rpm per inch of pitch, & got a 9. That was way too small, I was on the Rev limiter at 1/2 throttle. Yes same diameter, all oem aluminum props.
What prop have you been running? Acceptable performance?
As a frame of reference, I have Mirrocraft f3614. I re-powered with a Yamaha F25swhc back in 2017. The stock prop was
11-1/4 pitch, WOT was 24ish MPH @ 5400 RPM. I changed to a 10-1/2 pitch, WOT is 26ish MPH @ 6100 RPM