Dustin or SteveDavid

[XLGPP]

more questions on the XR with sportmaster. The shop working on my drive said they have talked to several ppl and mercruiser, all saying that the sportmaster is a waste of time and money unless your pushing over 100mph... I am getting right at 100mph at havasu, which is once maybe twice a year I go there.. At my lake (4500ft) Im getting close to 90... You guys seem to know better than anyone else, so I would appreciate your opinions on this..
thanks
Aaron

[SteveDavid]

Hi Aaron,
The Sportmaster really comes into play above 90 MPH and in higher X dimension set ups. The shape of the lower unit bullet enhances laminar flow (water along the surface of the unit) thus directing more undisturbed water to the propeller. Above 90 MPH a bravo drive begins to generate blow out, or essentially a parting of the water over the outdrive bullet and separating the "solid" water before it gets to the propeller. As a result slip factor or inefficiency increases dramatically. We've used larger diameter 4 blades and 5 blades to help but that induces other changes such as stern lift.
In your application, to maintain skiiability and a broad range of uses, you're fine with the XR drive and may enjoy a small increase in speed 2-4 MPH with a sportmaster. If you happen to break a drive,(let's hope not....) I would then upgrade to the sportmaster, and possibly the 2 inch shorter unit if that will still get you on plane easily. As time progresses the price of these lower units (sportsmaster) will decrease and there may come a time where you can pick up a good used one for a reasonable price <$2,000 and have it as a spare or for swapout. It will bolt up to your existing Bravo upper.
Hope this helps, have fun!

[XLGPP]

thank you, the way i see it, if I have the opportunity now to put on the sportmaster and not have to mess with it again, all the better, plus i dont want to have to lose too much speed going from the xz to the xr. In addition the sportmaster will give me flexibility to possibly go with a smaller pulley and get to that 100mph at 4500 ft. (if i want to increase chances of motor probs).

[SteveDavid]

Aaron,
The XR really doesn't take anymore HP to turn than the other Bravos. The theory was that the staight cut gears had greater parasitic loss but we've not seen that on the water. If you're going to up your boost i would HIGHLY recommend using the XR. The Sportmaster lower should be fine. The skeg on the sportmaster is 2 inches deeper so if you run the same x dimension you might notice a little more torgue pull on the wheel. On the other side, it tends to reduce chine walking on Vee bottoms and provide more lateral stability on Cats.
take care,
Steve