Prop pitch for Tohatsu 18 hp and SIB

[dhaglund]

Does anyone know approximately what prop size would be good for a Tohatstu 18 hp 2-stroke (M18) on a 3.7m SIB (Zodiac Futura IIc)?

Tohatsu suggests 9.3 X 10 or 11,5 for a light boat.
Prop Chart

But I would appreciate to hear from someone that has this engine or very similar on a SIB.

[Fenlander]

Much depends on your load but usually a 20hp will run a 10" or 11" on an average 3.8m SIB.

My experience was with a 20hp Suzuki efi on my Aerotec. 11" as supplied was just OK but 10" far better. That was with 26st of adults plus a teen around 8st, dog, 25l fuel and kit.

Most 15hp 2-strokes came with a 9" pitch and the Yamaha 15hp 2-stroke often a 9.75"... so I can't see you needing less than a 10" pitch.

[dhaglund]

Thank you.

10-inch pitch sounds about right then.

[dhaglund]

I bought a 10" pitch propeller. Specifically a Solas Amita 3 3X9 1/4X10 (part #5111-093-10) since Solas seems to be the OEM for Tohatsu.

I tried it today and it works great with 2 large adults (200 kg) onboard. Unfortunately the tachometer was acting up so I couldn't get a good reading to confirm the max rpm. Top speed was 22-23 knots.