Prop noise 1200-2000 rpm

[Cat18]

In order to get on plane quicker I replaced a 3 blade, 14x17 aluminum prop on a new 70Ahp Suzuki with a 4 blade 13.5x15 Turning Point aluminum prop. It planes much better but has a very noticeable whine from 1200-2000rpm. The original 2000 70hp Suzuki had a S Steel 4blade, 13.25x15 prop that had no noise. I did run the prop out of water at those rpms and had no whine. The boat is a light weight 18' Seagull catamaran.

 

[Texasmark]

In order to get on plane quicker I replaced a 3 blade, 14x17 aluminum prop on a new 70Ahp Suzuki with a 4 blade 13.5x15 Turning Point aluminum prop. It planes much better but has a very noticeable whine from 1200-2000rpm. The original 2000 70hp Suzuki had a S Steel 4blade, 13.25x15 prop that had no noise. I did run the prop out of water at those rpms and had no whine. The boat is a light weight 18' Seagull catamaran.

Swag. Your TP probably is ported...holes under the leading edge of the blade designed to allow exhaust gasses to flow across the blades in the hole shot allowing for fast RPM increases and faster HP development which gives you a faster shot. The air/exhaust gas across the blade could allow for a humming sound.

At WOT and max trim I have experienced hum with a Mercury Laser 3 blade, non ported, 13x19 on a 115 tower of power running at 6k RPM. The engine was singing and the prop was beating the surface....very definite hum.

 

[Cat18]

Thanks , just wanted to make sure there was no damage being done. I can put up with the whine in a rpm range I don't stay in long.