The Right Gearcase: Sport Master, Torque Master, Nose Cones
Your gearcase is critical to your boats performance. With so many gearcases out there and some cone options, sometimes it’s hard to figure what is best. Let’s take a look at some stock cases, nose cone options and more importantly, what application is best for each one.
We can’t really talk about every gearcase but we can look at the most popular and then see why some nosecones work and how. The general rule of thumb for Mercury Racing gearcases for outboards is the 85 MPH mark. If your boat can run up to about 85 MPH, the Torque Master is often best and if you exceed 85 MPH then the Sport Master is best. This is a great rule of thumb but there are a few caveats that apply to these and other gearcases.
Incredible picture showing a tunnel with a look at the gearcase and how it runs. Reducing drag is the key to performance, not much drag here. (Photo credit: Mercury Racing).
First, there are some applications that require a surfacing gearcase even if they don't’ meet the 85 MPH mark. For example, a really light V pad hull like an Allison, Bullet or Hydrostream still needs a surfacing case, even with modest power, because you want to reduce drag as much as possible. The ability to raise the engine where the prop shaft is close or above the pad means your high speed handling will improve dramatically, as well as your ability to maximize the efficiency of your prop; in those applications. The same is true for a light tunnel or center pod tunnel. Dragging the gearcase submerged on light performance hulls won’t allow you to realize the efficiencies of the hull.
Our project Allison Grand Sport didn’t exceed 85 MPH but the hull needs to run the gearcase high to achieve maximum efficiency. Reducing drag is efficient and helps handling on a light fast boat like the Allison.
Where it gets tricky is you want’ to find that gearcase height that maximizes the efficiency of the prop without slipping too much and insuring you have adequate water pressure. This is where the low water pickup on a coned case works and also changes the dynamics of the case. Surfacing a case changes the character of the performance dramatically in a few ways.
One, when the case is surfacing at speed, there is lift generated by the gearcase itself because you have tremendous water pressure on the bottom of the case and almost none above; hence a lifting effect. A semi surfacing gearcase like a Torque Master or even a Yamaha VZ gearcase can run pretty high and generate lift but not like a surfacing case due to the water pressure on the high side of the case. Semi-surfacing gearcases have advantages that I’ll get to next. The key is with a surfacing case is that now you don’t need as much positive trim if any and your setback is a more critical setup feature as it can determine some degree of bow lift.
The Suzuki V6 case is sleek and has dual water pickup. Competitive with the Torque Master and Yamaha VZ case.
Running a surfacing gearcase means you may want more setback as you will generate natural bow lift with less trim that way. This is obviously dependent on hull design, weight, speed and other factors but generally speaking, getting the setback right is critical.
This is a Speed Master on the new APX series race engines. Incredibly slim and designed to run at extreme heights for racing only. It won’t work on any conventional hull in the way intended.
When it comes to maximizing performance on boats that are somewhere in the middle, they can run into the eighties or close, are reasonably light but no getting major natural lift above certain speeds, the semi-surfacing cases like the Torque Master and other stock cases can actually be faster in some cases. Swapping to a Sport Master or coning a gearcase won’t make certain boats faster and in fact will often slow them down. The longer shape causes more drag when not surfaced. One determination is speed and the others are the use of the boat, design and handling.
When I repowered my 22 Activator recently, that boat falls into the camp of being right in the middle. If we went with 300 HP, I would opt for the Sport Master and probably would add a little more setback. Instead, we went with a 250 Pro XS and kept the Torque Master because even if I’m close to the 85 MPH mark (Torque Master’s generally max out at 86-87 MPH), most of the time I will have a greater benefit with the TM case. I can still run it quite high and at speeds under 80, it’s often more efficient, plus generally it can hold the bow better with trim. My boat is really heavy too, so a Torque Master with the right prop should run a little better overall in my case with 250 HP.
Dual water pickup is common and semi- surfacing cases like the Torque Master 2 here can be run pretty high. The shape is for slightly heavier loads, bow lift and can run up to around 85 MPH. Features the same heavy duty prop shaft as the Sport Master.
For engines that came with less performance oriented gearcases or lower HP engines that are on really light fast hulls, nose cones are great. Here’s a link to our look at installing a Bob’s Machine case. For instance, on our Allison Grand Sport project, the 150 Mercury doesn’t have a low water pickup so is extremely limited in engine height. I think I could maybe get it to the low 70’s but you could feel it want to chine walk, and the drag was causing this as well as slowing it down. Despite not being able to exceed 85 MPH, the Allison needs a surfacing case to allow the hull to perform as it should. This is why the 85 MPH speed mark is a good rule of thumb but not the only factor.
Mercury Racing Sterndrives range from Bravo drives with Sport Master Gearcases and M Racing drives like this for extremely high speeds. Criteria for heavier fast boats with big power is much different than small outboards.
As always, experimenting with your particular boat is part of the fun. Even a stock case can be raised, as long as you have water pressure and you can always try more setback. You could even try a remote water pickup. As you go higher, your propeller needs can change dramatically. Additionally, if you increase your setback, keep in mind the water rise off the transom goes up slightly the further back you go; usually just slightly, depending on boat weight and design. So the answer to the question: what gearcase do I need? Is, it depends. Test, drive safe and have fun.
Here’s a great blog post from Mercury Racing about gearcase hydrodynamics: Gearcase Hydrodynamics
