boatnut
07-15-2006, 10:04 AM
Many moons ago I shared some data and handling characteristics resulting from using a Bravo 1 28" pitch on my 22. I have (finally) now tested with a Turbo 1 23" and here is the comparison.
Handling: the boat porpoised at all but higher speeds with the Bravo 1 28 and needed tabs down below 45mph. With the Turbo 23" the handling is better (less porpoise) and I can run below 45mph without tabs but the slightest wave action will cause porpoise -- the Turbo didn't help as much as I hoped but based on all of your input I think it is probably the best prop for handling on this hull. The bottom of my boat seems to be straight but acts like it has some rocker ---it surely doesn't have the hook that my 18 has.
Speeds: The engine is the 1997 Gen VI 7.4L rated at 300hp (carb), suggested to be run in the 4200-4600 range. Bravo 1 1.5 ratio. (Does anyone know when the rev-limiter is supposed to kick in on this engine?). It seems pretty obvious that my tach must be inaccurate. I show the tach reading and (90%) of tach reading but the error is probably more at full rpm and not linear. Next goal is to check or change the tach. Speeds are GPS. Approx 1/2 tank fuel, 2 people, tabs up.
RPM, (90% RPM), Bravo 28, Turbo 23, Trim
3000, (2700), 37.8, 30, in
3500, (3150), 45, 37, in
4000, (3600), 54.5, 45.5, yes
4400, (3960), 60.4(wot), n/a, yes
4500, (4050), n/a, 51.5, yes
5000, (4500), n/a, 57, yes
5400, (4860), n/a, 62(wot) yes
At this point my plan is to stay with the Turbo 23, change or correct the tach, and try to come up with a tab usage that makes this gorgous boat settle down a little (while hanging on to the 62 mph which I think is about all that can be expected from 300 hp). Knowing I am probably going to upset most of you, I think the ideal engine for this hull is about a 350hp small block. I think there are better hull designs for going over 70 with improved stability(here come the missles). Thanks for your ongoing feedback, Ed
Handling: the boat porpoised at all but higher speeds with the Bravo 1 28 and needed tabs down below 45mph. With the Turbo 23" the handling is better (less porpoise) and I can run below 45mph without tabs but the slightest wave action will cause porpoise -- the Turbo didn't help as much as I hoped but based on all of your input I think it is probably the best prop for handling on this hull. The bottom of my boat seems to be straight but acts like it has some rocker ---it surely doesn't have the hook that my 18 has.
Speeds: The engine is the 1997 Gen VI 7.4L rated at 300hp (carb), suggested to be run in the 4200-4600 range. Bravo 1 1.5 ratio. (Does anyone know when the rev-limiter is supposed to kick in on this engine?). It seems pretty obvious that my tach must be inaccurate. I show the tach reading and (90%) of tach reading but the error is probably more at full rpm and not linear. Next goal is to check or change the tach. Speeds are GPS. Approx 1/2 tank fuel, 2 people, tabs up.
RPM, (90% RPM), Bravo 28, Turbo 23, Trim
3000, (2700), 37.8, 30, in
3500, (3150), 45, 37, in
4000, (3600), 54.5, 45.5, yes
4400, (3960), 60.4(wot), n/a, yes
4500, (4050), n/a, 51.5, yes
5000, (4500), n/a, 57, yes
5400, (4860), n/a, 62(wot) yes
At this point my plan is to stay with the Turbo 23, change or correct the tach, and try to come up with a tab usage that makes this gorgous boat settle down a little (while hanging on to the 62 mph which I think is about all that can be expected from 300 hp). Knowing I am probably going to upset most of you, I think the ideal engine for this hull is about a 350hp small block. I think there are better hull designs for going over 70 with improved stability(here come the missles). Thanks for your ongoing feedback, Ed