Propellor Pitch 23 vs 21 degrees

[JohnnyMW]

As you know I have bought an Osprey Vipermax 5.8 with a Suzuki DF140 on the back. I have two props one with 23 pitch (currently fitted) and a spare with 21 degrees if pitch both same diameter.

The boat was previously a dive boat but have just added 4 x pod seats to carry the family. Any thoughts on which prop I should use? Pro's/ Con's of each?

Thanks again

[Pikey Dave]

Try 'em. We can sit & speculate all day, but there's no substitute for sticking them on & having a go. Load the boat up with your "normal" load & go WOT. You should be able to get close to your engines max RPM at WOT. The difference between the 2 props will be around 400rpm. i.e. the smaller prop will run around 400rpm faster than the biggun.

PS Pitch is measured in inches not degrees.

[JohnnyMW]

Originally Posted by Pikey Dave

Try 'em. We can sit & speculate all day, but there's no substitute for sticking them on & having a go. Load the boat up with your "normal" load & go WOT. You should be able to get close to your engines max RPM at WOT. The difference between the 2 props will be around 400rpm. i.e. the smaller prop will run around 400rpm faster than the biggun.

PS Pitch is measured in inches not degrees.

Thanks for your thoughts! And clarification on inches! I'm still learning! I'll try both and see how I get on. I've heard a lower pitch will give better fuel economy too!!

[Pikey Dave]

Originally Posted by JohnnyMW

........ I've heard a lower pitch will give better fuel economy too!!

Could go either way, propping is a black art & there are no hard & fast rules. That's why you need to experiment. If the engine can spin it, the higher pitch will give you more top speed, but lower "holeshot" (acceleration) & vice-versa for the smaller prop. If you cruised all day at a constant-ish speed, the taller prop could in theory give better economy, but would use more fuel accelerating, so like I said, trial & error.

If you're going out lightly loaded for a jolly on a calm day, stick the bigger prop on. Fully loaded, rough seas, towing toys, skiing etc. then the smaller prop will probably be the better option IF you can achieve WOT (Wide Open Throttle) RPM i.e. full beans, pedal to the metal etc.

[JohnnyMW]

Originally Posted by Pikey Dave

Could go either way, propping is a black art & there are no hard & fast rules. That's why you need to experiment. If the engine can spin it, the higher pitch will give you more top speed, but lower "holeshot" (acceleration) & vice-versa for the smaller prop. If you cruised all day at a constant-ish speed, the taller prop could in theory give better economy, but would use more fuel accelerating, so like I said, trial & error.

If you're going out lightly loaded for a jolly on a calm day, stick the bigger prop on. Fully loaded, rough seas, towing toys, skiing etc. then the smaller prop will probably be the better option IF you can achieve WOT (Wide Open Throttle) RPM i.e. full beans, pedal to the metal etc.

Thanks I'll give that a try and let you know how I get on. I hasn't realised there was so much to learn.......!!!!! Much appreciate your time. Cheers