Originally Posted by redthunder
. A guy on another forum said that I was getting 11% slippage which is good.
That guy (on THT, Ken from Propgods) is probably one of the best Prop guys on the planet, I would take his advice as he really does get great reviews and seem to know his stuff, although not necessarily for Ribs.
I have REV4 19", it really does grip in the rough and when cornering hard, it will happily bog down the motor on the back of my boat rather than slip. The Rev 4 is a stern lifting prop, and should allow you to plane at lower speeds, I can hold 10 knots on the plane which is pretty impressive for a big lump but you will not get the top speed or economy that you would from a well sorted three blade. Cruise and slow speed handling is often improved with a 4 blade as well.
Usually sold in 2" increments, Merc have just bought out (or are just about to) some new REV 4 models and I think one might be a 20, as well as some smaller pitch counter rotating ones. Might be worth checking with and a dealer or doing a search.
I have tried a three blade on mine and it was hilarious, just spun up to 5000 rpm with no increase in speed, had to coax it onto the plane, but was slightly faster when it got there.
If you can get a new Rev 4 for £500 I'll have one too!
Best of luck with your research and finding the best prop for your boat.