18' with Merc 115 (1988 Both of them) Best Prop?

gofastsandman · #1 10-29-2009, 07:47 PM

Quote:

; I also tried a 3B SS 15 1/4 x 17P Mirage 3+ that everyone raves about, but the Apollo turned the same rpm, was about 3 mph faster, would plane about 5 mph slower and was about .5 mpg better in fuel consumption!

That left a mark.

Chagrin, chagrin chagrin. How did he do that. Top end too? More stern lift= less wetted surface = more mph.

GFS
Going out this weekend D. ?
Any good stories from O.F.F. ?

Bushwacker · #2 10-29-2009, 10:30 PM

[/QUOTE]. . . How did he do that. Top end too? More stern lift= less wetted surface = more mph.

GFS
Going out this weekend D. ?
Any good stories from O.F.F. ?

[/QUOTE]

Hey Sandy,

I can't really explain it other than maybe it's just a more modern, more efficient prop; maybe less slip with 4 blades. More stern lift SHOULD produce MORE wetted surface and more drag. However I could trim the motor higher with the Apollo before it started to porpoise than with either the Mirage or PowerTech props, so that might explain the higher speed.

Will not get out this weekend; but did fire up the motor a few days ago. Wife had emergency surgery on her stomach 3 wks ago, so still playing nursemaid! May get out sometime next week.

There was some great movie footage of old races; I had asked Skip if he was gonna bring the 21, but he said no, it's not ready yet. Well, there was an old Bertram Moppie there in early restoration (teardown!) phase with the drives and engines removed, but nothing more had been done on it, so I think he may reconsider for next year!

Denny