OK, Bravo 1 to Bravo 1 sportmaster lowers. Uppers are the same as before 1.36 XZ's. The lowers were bought empty and my XZ large prop shafts and gears were installed with new bearings by a Mercury facility.

Props tried B1 34's labbed without diffuser, B1 35's labbed with diffuser, and 33 Q5's labbed without diffuser ring.

The rev limiter was moved to 5700 two years ago.

Too much drag...most likely. I can't believe I am the first one to learn this.:eureka:

Sportmaster Lowers
 

John,
It is surprising that the Sportmasters are slower at 110+ mph than the std. Bravo lower at the same "X". From what I have learned in back to back comparisons, the Sportmaster lower unit is 1 to 1-1/2 mph slower than the IMCO unit at the same x dimension ( Two cat's and one "V" ). These comparisons were at 105 - 115 mph. Most opinions related to the speed difference were skeg length or thickness. I wonder if the water pick up design on the Sportmaster vs. the IMCO or the std. Bravo unit is causing a decrease. As there is a chance that the speed loss is related to this, maybe you can temporarily plug a few Sportmaster water pick-up slots for a test.
Could you have a temporary loss of HP that is effecting the test results?
If you need your 1/2" spacers back, I not using them... Remember, it's all about the hunt.
Good hunting,
Sprague

Quit foolin' around with that old cat, buy a Magnum and start enjoying boating again. See you on the lake.

Sprague, Anything is possible. I have waited until I tried half a dozen different days (temperature & humidity), loads, and tried all my props before this post. I am hoping to find someone with similar experiences before I start hacking away at Mercury's engineering marvel.

Bob, I hung upside down in your bilge for 5 years trying to run 80. Now I can sleep between my engines and get depressed if I only run 100.

Love the quote!!!

Everytime I think about doing something else to my boat I am told by friend "That change should only be good for a 4 or 5 mph lose"

I just found out Mercury sportmasters have (TWO) different styles of water pickups on these drives; a long system that the std. flush kit doesn't work on and a newer shorter style that the flush kit covers. I have the long style. Does anyone know what is up with this deal?

Appreciate your info on "things that don't work". I'm in the middle of a lab prop adventure that resulted in a negative 3mph. Labbers response was, "what happen to your engines?"

How do you just "raise an X dimension"? Isn't it set from the factory based on the length of the drive lower casing and where the drive is mounted to the transom? What am I missing? I know with outboards you use a jack plate to accomplish this but that can't be done with inboard/outboards rigs...can it? I thought the only way to adjust the X dimension once you get the boat from the factory is by installing a shorter lower casing.

Curt, This boat has Stellings boxes (drive extenders), which allow the drives to be raised or lowered 2 inches, without redoing the transom. Now I can go up or down 1 inch without to much trouble.

Has anyone sharpened the skeg on these sportmasters yet?

How about the water pick-up changes Mercury made?