Prop question for a 90 HP Johnson

[Firefighter615]

I have a 1984 Johnson, 90 HP motor that has a 13X19 prop on it. I have been told that a 17 or 15 would be better because with the 19 it will not get on plane. It sounds like there is not enough motor to turn this prop. Will a 17 be OK or should I look for a 15?

Thanks for all the help

[rickdb1]

What boat do you have it on and what are the current wide open throttle RPM's?

[Firefighter615]

The boat is a 1983 Ranger 372v, I have a tach but I dont think that it is correct because it says that it is trunning about 3500 rpm

[ChampioNman]

Should be able to spin a 19 OK. Unless you are pulling kids on tubes or skis. Then a 17 would be in order. I'd verify that the tach reading is correct. You may have other issues.