4 Blade or Not?

[DavidStevenson]

Hi - I have a similar question problem. I am new to the speed boat scene so please excuse me if I get a few things wrong.

I recently bought a Four Winns H180 running Mercruiser 4.3L MPI (WOT 4400-4800) on ALPHA 1.62 with an alum 3 blade 14.25x21P prop. Went skiing and had slow out of hole experience - I won't mention the 20 years since I last skied or the 20kgs I put on since but it was clear to the three of us on board the prop wasn't "gripping". There was also a HEAP of speed variation and had to constantly tweak the throttle to keep some semblance of speed consistency, particularly around the 14-20 knot wakeboard range.

I ran a speed test and only pulled 3500 RPM WOT but had 47mph. Entering these numbers into the various calculators questioned the speed for the RPM on this prop so I am now investigating the accuracy of the RPM but that's another story.

Question is on advice re a prop. I am thinking on going with 4 blade 19p alum but would appreciate other people's experience. Would a 14 or a 14.25 make much of a difference - I am reasonably ok with the reasoning around maintaining RPM in WOT range and overrev damage / labouring etc.

Appreciate people's input.

 

[GA_Boater]

Moved to a new topic.

Welcome aboard, David. For best results a new topic is preferred over tagging on to a 2 1/2 year old thread when you have a question. Thanks.

 

[Sea Rider]

Need to tach that OB with one up on flat calm no wind water cond, check achieved max wot rpm, see how much will rise compared to same wot run with 3 up. Tach must be in 100% operational shape. For skiing you only need 3 people, skier, spotter if required and driver. Need a fast hole shot. You can benefit having 2 props, a general use and a skiing prop.

Happy Boating

 

[Starcraft5834]

"Need a fast hole shot. You can benefit having 2 props, a general use and a skiing prop."

+1

for sure. if you only want (1) prop and you don't mind losing 1-3 mph top end, the 4 blade will do the best overall job. Solas makes good ones..

 

[DavidStevenson]

Thank you everyone. I'll get an external tacho on it and come back on via a new thread.

 

[GA_Boater]

Thank you everyone. I'll get an external tacho on it and come back on via a new thread.

No - This is the new thread. Post the info here.

The new thread comment was about asking questions in old, inactive threads. I moved the post from the old thread to this thread of your own. You can post in this thread at any time without time limit because you are listed as the original poster.