Tohatsu 9.8 prop

[pikl]

Hello, I would like to replace the standard propeller 8.5x8 on a tohatsu 9.8 short shaft for a heavier solas. The boat weighs about 700-800kg. At full throttle the rpm is 2600. There is not much difference in speed at half throttle and at full throttle. should I take solas prop 8.7 x 7, 8.7 x5 or 8.5 x 7? Thanks...

 

[Paul1962]

Your full throttle RPM sounds a bit low - I would expect at least 5000 RPM at wide open throttle

 

[pikl]

It's possible that the tachometer is not accurate. I would definitely need a cargo propeller due to the weight of the boat, but I'm not sure if it would gain at least a little speed with a 8.7x7 4 blade propeller or maybe an 8.7 x5 (if not too much) or an 8.5x7 3 blade.