BonBini
New Member
Just before I sold my 230 I took her out for one last ride to experiment with props and flame aresters. Since my 268 came with an extra prop and a big block, this is something I just had to do or regret forever:grin:. I thought some of you might be interested in my findings.
My test runs were all within an hour of each other over the same light chop water in the same direction. Gps mph readings and tach acuracy verified with my photo tach.
Boat had 1/2 tank gas, one person me @ 190#, and maybe 200#'s of tools, props, safety equiptment. This boat also had fresh bottom paint wich I think creats drag and aerates your prop.
40mph @ 5000rpm. 15x15ss stock flame arester.
40mph @ 4600rpm. 15x17alum stock flame arester.
43mph @ 5000rpm. 15x17alum 7.4L flame arester.
Conclusion: Merc sets the HP on the 5.7L 260 by controling the amount of air it can get with the flame arester. The 7.4L flame arester was taller and breathed maybe anouther 20 horse into her. The hype of Alum vs SS and blade flex; I think in this case under big load comeing out of the water maybe some flex is there, but up at planing speed no.(ie: the 268, 330hp will do 40mph gps @ 4800rpm w15x15ss or 15x15alum. did not try the 15x15 alum on the 230). enjoy ...Ron
My test runs were all within an hour of each other over the same light chop water in the same direction. Gps mph readings and tach acuracy verified with my photo tach.
Boat had 1/2 tank gas, one person me @ 190#, and maybe 200#'s of tools, props, safety equiptment. This boat also had fresh bottom paint wich I think creats drag and aerates your prop.
40mph @ 5000rpm. 15x15ss stock flame arester.
40mph @ 4600rpm. 15x17alum stock flame arester.
43mph @ 5000rpm. 15x17alum 7.4L flame arester.
Conclusion: Merc sets the HP on the 5.7L 260 by controling the amount of air it can get with the flame arester. The 7.4L flame arester was taller and breathed maybe anouther 20 horse into her. The hype of Alum vs SS and blade flex; I think in this case under big load comeing out of the water maybe some flex is there, but up at planing speed no.(ie: the 268, 330hp will do 40mph gps @ 4800rpm w15x15ss or 15x15alum. did not try the 15x15 alum on the 230). enjoy ...Ron
