TOPIC:

I got a new prop this year hoping for better performance in big water. At this point it seems to be a wise investment.

Old Prop:
Mercury Tempest 3 blade SS 21 Pitch. 3 Vent holes open (what size hole in the vent plug I am unsure)
Soft and week in big waves. Falls over the top rather easily.
Max Plan speed 19 MPH
Time to plane: Fast
Max RPM 5300

New Prop:
Mercury Bravo 4 blade FS 21 Pitch (All 4 Vent holes plugged)
Handles the big water much better (like having the truck in tow mode) Much more Torque
Max Plane speed 17 MPH
Time to plane: Faster maybe (Not as much bow rise)
Max RPM 5600 (have mot got her fully trimmed yet so probably even better)

Top end speed seems to be slightly better as well but it is tough to determine depending on guys in the boat, amount of fuel etc. It is definitely not slower but seems 1-2 MPH faster. Probably max out at 52-53 MPH. Overall its been a pleasant change in handling bigger waves.

Wow adding an extra blade helped you out big time. Kept the pitch the same and your rpm and speed went up. Is there a change in diameter also? Usually speed drops a little top end and lose some rpm. You will love the way it will keep the boat on plane at a much slower rpm. Probably will save you some fuel also. I will have to look into one of those props. Do they have the replaceable hub system? Bet it would work on other engines as well.

I switched from a three blade to a four blade prop with the same pitch on my Suzuki 115 fourstroke and noticed much better performance. More response, more top end and less rpm.

Steelie wrote:

Wow adding an extra blade helped you out big time. Kept the pitch the same and your rpm and speed went up. Is there a change in diameter also? Usually speed drops a little top end and lose some rpm. You will love the way it will keep the boat on plane at a much slower rpm. Probably will save you some fuel also. I will have to look into one of those props. Do they have the replaceable hub system? Bet it would work on other engines as well.

I believe the dia. of the 4 blade is a touch smaller. I got it after realizing my poor performance in big water was partially due to my prop not having a good grip on the water. The touch of extra top end was a bonus. I seem to have been over propped before a bit on the top end.