The Truth About Cavitation Plates

Daniel Freer & Kevin Shaw
The Truth About Cavitation Plates
Installed plate.
Cavitation plates are mounted to the lower units of boats to help increase performance. They act as a planing surface to get your boat on top faster. They give you better bow response when trimming your motor. They keep water down at your prop and intake improving water pressure. They help prevent against "blow out" when taking off shallow. Plates with wings can help boats track better when running. Different boats will see varying improvements depending on the type of boat. Tunnel hull boats usually see the most dramatic performance increase from cavitation plates.

There are so many different types of cavitation plates on the market. How do you know which one is the best? When we talk about cavitation plates, we do not mean hydrofoils or stingray fins. These types will help with planing and bow response, but they will not do anything for cavitation. True cavitation plates run from before the lower unit to past the prop.

Not all cavitation plates are created equal. Some plates claim to be universal, or "one size fits all". Lower units range in size and shape depending on horsepower rating and manufacturer. "One size fits all" plates can become loose and eventually damage a lower unit. Other plates require holes in the lower unit. When stainless is bolted through aluminum and introduced to saltwater, you get electrolysis, which speeds up the corrosion of aluminum. This also applies to aluminum cavitation plates. Some plates have a narrow edge sitting on top of the lower unit plate. These plates groove the cast aluminum of the lower unit, eventually sawing off the edges! Most plates collect enough floating grass to make a salad. It becomes wedged so tightly that it is almost impossible to remove. Some plates are "finished" on the topside and rough glass on the underside. Water travels underneath the plate, not over the top. The underside should be smooth.

Now let me tell you about the cavitation plate with the least amount of drawbacks. The Stiffy ShawWing cavitation plate is a clamshell design that clamps over your motors' existing cavitation plate. The bolts do not go through the lower unit. Each plate is notched to fit the motor it will be installed on. We have over 60 different notches for all major manufacturers. When we install the plate, we liberally apply marine grade silicone to all areas being sandwiched together. We also caulk a clean bead around every seam of the plate to prevent grass from becoming wedged. When installed correctly, our plates will not become loose, and will not damage the lower unit. The wings on our plates deflect water back at the prop and help with tracking. When your prop keeps more water, RPM's stay down. When your intake keeps more water, pressure stays high, and your motor runs cooler. A ShawWing can help prolong the life of your motor.

We have 4 different sizes of plates. Small, Small Plus, Medium, and Large. Several factors come into play when deciding which size plate is best for your boat, please call or e-mail with your specs and we can tell you what is best. Generally speaking, the Small plates work best on 25 70 hp motors. The Small Plus plate is longer than the regular small, and will work on some 90 hp motors. The Medium plate is for 90 hp motors and up. Boats with inset or "key slot" transoms will most likely need a medium to keep the plate from coming in contact with the sponsons while turning. The Large plate is typically installed on 115 HP motors and up. It has the largest planing surface of all the plates and is usually installed on boats with a flat transom. Plates are notched to order, mounting hardware and Sikaflex marine silicone can also be included. Detailed mounting instructions come with every plate we send out.

Several boat manufacturers install our plates on their boats at the factory. Other manufacturers recommend our plate on their boats. ShawWing Cavitation plates are made with biaxial glass with extra laminates on the front end. This allows us to make a plate with higher strength to weight characteristics than a plate made entirely from mat fiberglass.

By now you're saying, "You pointed out the drawbacks of all the other plates. What about yours?" Sounds fair to me. Our plates are not notched for the trim tab anode above your prop. Which means the plate has to be removed in order to replace this part. Which can be tough since the plate is glued on. However, we can notch out the area if we install the plate ourselves. Or, if you order a plate, you can cut out the area for the anode before installing the plate. If your trim tab anode is looking a little rough, replace it before you put the plate on. They are relatively cheap and usually last many years depending on how well you maintain your boat.

Yes, our plates may be a little more expensive than others. By now you should realize why that is the case. If you want a better boat, it is going to cost more. You want a smoother reel and a lighter fishing rod, they are going to cost more. You get what you pay for. If you want to save yourself a few dollars and buy the cheaper plate, it could cost you more in the long run. You don't have to take our word for it, next time you see someone with a ShawWing, ask them what they think.

Next article we will cover the topic of push poles. We will answer the common questions and clarify all the misconceptions. Who knows more about push poles than your boys here at Stiffy?! Stiffy Brand Push Poles are the leading push pole brand in the world.

Go Fishin' Ya'll

FiberTex & Supply - Manufacturers of Stiffy Brand Products
7533 Bay Dr.
Corpus Christi, TX 78414
[email protected]