Hi there
I own a 12 ft rib (inflatable rigid boat), 200 lbs net weight, 480 lbs gross with outboard, fuel, cockpit, seat etc. Usually two adults on board (2 x 180 lbs). Thus, total weight with passengers is about 840 lbs.
The outboard is a new Yamaha F15C, 4 strokes, with power tilt and remote control (5000-6000 full throttle operating range).
Currently using a Yamaha 3 Blade Alloy propeller 9 1/4 x 9 pitch (I have changed the 10 pitch that came with the outboard because it was over-prop for the boat).
All the weight is back (driver seat and fuel tank).
The boat gets on plane with two adults on board but never with three. (If the two adults are sitting on the driver’s seat I have to stand up and make a small step forward in order to get on plane. If one of us is sitting in front everything is OK, no need to step forward.)
With two adults the numbers are as follow:
RPM @ WOT: 5600 and the top speed just below 19 mph.
At 5400 rpm, 17 mph
At 5000 rpm, 15 mph
If I drop from 5000 rpm the boat loose planning and the speed falls to 8 mph. So, my useable range is just between 5000-5600 rpm.
With three adults: the max rpm are 4800 and no planning.
With just me the max rpm are 5800 and the top speed 21 mph.
I tried a solas 8” 4 blend but there was not any improvement.
I own a 12 ft rib (inflatable rigid boat), 200 lbs net weight, 480 lbs gross with outboard, fuel, cockpit, seat etc. Usually two adults on board (2 x 180 lbs). Thus, total weight with passengers is about 840 lbs.
The outboard is a new Yamaha F15C, 4 strokes, with power tilt and remote control (5000-6000 full throttle operating range).
Currently using a Yamaha 3 Blade Alloy propeller 9 1/4 x 9 pitch (I have changed the 10 pitch that came with the outboard because it was over-prop for the boat).
All the weight is back (driver seat and fuel tank).
The boat gets on plane with two adults on board but never with three. (If the two adults are sitting on the driver’s seat I have to stand up and make a small step forward in order to get on plane. If one of us is sitting in front everything is OK, no need to step forward.)
With two adults the numbers are as follow:
RPM @ WOT: 5600 and the top speed just below 19 mph.
At 5400 rpm, 17 mph
At 5000 rpm, 15 mph
If I drop from 5000 rpm the boat loose planning and the speed falls to 8 mph. So, my useable range is just between 5000-5600 rpm.
With three adults: the max rpm are 4800 and no planning.
With just me the max rpm are 5800 and the top speed 21 mph.
I tried a solas 8” 4 blend but there was not any improvement.
- I would like to get on plane with no difficulty and also to get to plane with three people on board. Should I replave propeller? Do you suggest 8 or 7 pitch? Should I try a stainless one?
- My propeller is mentioned as J1 hub. Is there a difference between J1 and J hub? This is crucial because the shorter J1 propeller is 9 pitch. The available propellers with shorter pitch are with type J hub.
- Should I replace propeller anyway? What about if I decide finally to travel only with two adults on board? In that case I should remain at 9”?