I purchased a 2002 Fountain Fever this spring. This boat was tested at Fountain on a 40 degree day and ran 77 MPH @5350 rpm with a mercury 26p. After my sea trial I felt that the boat need more prop (it ran 5400 rpm speedo does not work) so I made it a point to look what was on it. It was a mercury bravo 24p. After delivery this is when I discovred that there was a 26 on it during testing. So I purchased a Mercury 26 but it will only turn 5000 rpm on a 100 degree day. I feel that a 350rpm is too much of a differance for 60 degrees. I felt that the drive gearing could have been changed out on a repair but after discovering that a 1.5 ratio was the steepest ratio available on a bravo xr I became stumped. Is it possible for some one to repair this drive by changing the lower case w a Bravox or something. to come up w a !.65 ratio . All serial #s match and the 500efi purrs w/ 100 hours. thanks Chris.

Chris,
Let me get this straight, they water tested with the 26p in 40* weather. They delivered the boat with a 24p and now you upped it to a 26p and in 100* heat, you can only spin it 5k rpm.
Well, two things. One is that you could be down a ton of power with the temp difference. The other is that unless you tried the same prop they used, you dont know if your 26p is killing some rpms. If the 26p (that Fountain used) was labbed it would account for at least a couple hundred rpm. And the heat could kill a couple hundred rpm also.
You have to compare apples to apples. The XR can be had with 1.5, 1.35, or 1.25 gears. With the 1.65 is a combination of different upper and lower gears.
I think your issue has to do with lack of power with the hotter weather. A loss of 50-75hp is not uncommon in some situations.

Hope this helps.
Dick

You could easily be loosing 350rpms from 40* to 100* with other factors in mind. Chances are they ran the boat with minimal fuel, and 1 or 2 people in ideal conditions with a 1 foot chop. What altitude are you at vs the Fountain Factory. That could be good for 100rpms or more also. Also, humidity plays a major factor. The original prop could have been labbed as well and that alone would account for the 350rpms.
Just get the 26 labbed for 200 more rpms and call it good.