For those of you who may not know me, I manage Mercury Racing’s propeller department. We offer a wide variety of high performance outboard and sterndrive props. We also provide customization and repair services. I oversee production and manage our prop offerings. My most enjoyable responsibility is helping customers solve their unique propeller issues.
Pro Finish Bravo I XS outboard propeller.
Allison XB-21 BasSport 2 + 2. Photo courtesy of Allison Boats.
I’ve been getting great feedback regarding our Bravo I XS outboard propeller. The latest is from Allison owners who say it is an awesome prop for their XB-21 tournament bass boats. XB-21′s rigged with an OptiMax 250 Pro XS do best running a 27-inch pitch Bravo I XS. Those who power-up to the OptiMax 300XS say their ride is dialed-in using a 29-inch pitch Bravo I XS. XB-21 owners have found odd-pitch Bravo I XS props provide the best hole shot and bow lift.
How They’re Made
So, I bet your wondering, “Did I just read that right? Bravo props for outboards? I thought they were for Bravo One sterndrives?” Well, you’d be correct on both points. We designed Bravo I XS (new in 2010) and Lab Finished Bravo I (featured 1998) prop for low-emissions, 2-stroke OptiMax outboards. And they are derived from Bravo I props for sterndrives.
Lab Finished Bravo I sterndrive propeller.
Pro Finish Bravo I XS outboard propeller.
Standard Bravo I propellers are cast in even, two-inch pitch increments (22″ to 36″). To use the Bravo style prop on 2-stroke outboards, we needed to expand the range of pitches. We added odd-pitch sizes in one-inch increments. We do that by increasing blade cup height on even-pitch castings — making them behave like “taller” pitches. For example, the 27-inch Bravo I XS (part number 48-831914L80) begins life as a 26-inch pitch Bravo I XS casting. Additional cup on the trailing edge of the blades differentiates a 27-inch pitch XS from a 26-inch pitch model. The part number for a 26-inch pitch Bravo I XS is 48-831914L60. The base part numbers for 26 and 27-inch models are the same. L80 designates higher blade cup height.
Another birthmark differentiating a Bravo I XS from standard is the addition of four, one-inch vent holes on the prop hub. The holes add prop blade ventilation. The engine spools up faster for enhanced hole shot.
One more difference is the tuned exhaust tube: we’ve shortened the tube for less drag at wide open throttle (WOT), picking up another one mph over a stock Bravo I.
Performance Results
Here's a good example of an elevated engine height featuring the surface-piercing Sport Master gearcase.
Allison XB-21 BasSport Pro. Photo courtesy of Allison Boats.
You may not think a slight change in blade cup height would have a big effect on performance – but it does. In the case of an Allison XB-21, the performance difference between a 26-inch and 27-inch pitch Bravo I XS is 150 rpm at WOT. If a 26-inch pitch allows an engine to rev to 6000 rpm at WOT, then a 27-inch pitch would typically lower rpm to 5850. The reduction of 150 rpm provides “a window of performance opportunity.” Its like free horsepower! — or a second chance to dial-in the boat for maximum overall performance. A slightly bigger, cupped, 27-inch pitch prop might stay hooked up longer, allowing a tick more trim for additional bow lift and offer higher speeds. It may also allow increased engine height of 1/4 to 1/2-inch. If the motor can be raised, without sacrifice safety or performance, one will usually regain 50 to 75 rpm, resulting in a higher top-end speed and better overall boat performance.
OptiMax 250XS powered Bullet 21 XDC.
The Simmons Custom Boats catamaran flats boat. Photo courtesy of Eric Simmons.
Cup plays an important role bringing a boat on plane and affects bow lift. Running an odd-pitch Bravo I XS, with its tall blade cup, can actually scrub top-end speed on boats that have natural bow lift. For example, air-entrapment tunnel hulls from Simmons Custom Boats typically run best using even-pitch Bravo I XS props.
The Bravo I XS is also popular on Bullet Boat’s 21 XD with OptiMax 250 Sport XS or OptiMax 300XS power. Bullet owners tell me a Bravo I XS provides great planing and mid-range punch while giving up little top-end speed. Tournament anglers say weight doesn’t seem to affect performance as a Bravo I XS “…carries the load, no matter what we throw in the boat.”
The Bravo I XS is available from 22″ to 31″ pitch, see your authorized Mercury Dealer to order.
There you have it. We sweat the details to ensure people enjoy high performance on the water. I’ll be back with more tips, helpful hints and insights regarding high performance props.
Hi Scott, great article! I actually have a lot of question’s about this prop and the set up regarding it and its modifications. I currently own two performance boats that I will be running Bravos on.
The first one is a 25 Liberator with twin 2007 300xs’s. I have a set of 32′s on it now that have been thinned and the one inch hole put in them. They are a WORLD of difference from the clever style props I was trying to run. They do tote the load a lot better too, and hole shot is MUCH better as well. I don’t think the hubs have been shortened on these particular props and wondered what the performance change would be if we did shorten the hubs on the 32′s? I am running 5 inch set back on the Liberator (which is suppose to be the same hull as the 24 skater). I am not sure how to set up the engine height with the Bravo props, do they like to be higher, Lower or ?? I have them set at 1″ above the bottom of the boat now and have left it there just to get more seat time in the boat with passengers. I have been very impressed with the Mercs and the Bravos so far, but I think its time to tweak it a little. The motors are on 49 inch centers, and I have turned it around 5700 so far. It doesn’t seem like the boat is airing out like it should from what I can gather from others who have the 24ft hulls. I recently purchased a pair of 30 p Bravos that I want to try, but I need to get the holes drilled and whatever else that needs to be done to them. My 25 Liberator is 1991 that I had to basically restore myself, took me about 4 years because I am a stickler for getting things right.
I too was raised like you from a young age on boats, my first performance boat was a 14ft Hydrostream Vandal with a modified 140 Johnson, shorty mid section and of course a 26″ Mercury small blade chopper, I sure do miss that boat, even though I still own a Hydrostream, which brings me to my next question.
This Hydrostream is a 20ft model called a “Vantage XT’ . the XT is the modified tunnel bottom and I just purchased a 250xs to bolt to the transom. This boat has run 87 mph with a 225 ProMax and a “homemade” 4 blade prop (from two 2 blades). I am hoping to get it to go that fast again with the 250xs and was curious as to what your thoughts were on how this setup would perform with a Bravo 1 prop? the boat currently has 10 to 12 inches of set back. The motor has 1.75 to 1 gears and a torquemaster style lower unit with the water inlet holes in the nose. This is NOT a sportmaster. I know I should have a sportmaster if the boat goes much faster than 85mph, and plan to swap it when I find one.
I have always had the v bottom boats over the years like the Hydrostreams and Allisons, that’s why I have given the big cat boat a lot of seat time before I start playing with the set up. Any and all help will be much appreciated. Thanks for your time and hard work to help us little guys have fun.
Sincerely Capt. Chuck Darring
Orange Beach , Alabama
Hi Chuck,
Thanks for the questions, comments and sharing about your restoration project. Starting with the 25 Liberator and twin 300XS’s, after you get comfortable driving the boat supply me with WOT RPM and GPS speed. The numbers will help me get a feel for your set up. Bravo I vented Lab Finished props are a great for everyday running but if you’re looking for the top number you may end up running 3 blade Cleavers. The exhaust tube flare on the Bravo I can help roll the boat over while planing along with offering stability at WOT. The Bravo I XS family was designed for single outboard applications where typically the flare isn’t required during planing.
The Hydrostream set up will be allot of fun. The 30″ pitch Bravo I that you already have will be a good starting point provided you install the 1″ vent holes in fact you may even require 4 additional holes to help break the big prop free. But one step at a time, let me know what you get for performance.