What to Know When Adding a Swim Platform to Your Boat
May 18, 2022 5 min read
Let's face it, getting in and out of your boat can be a challenge, and there's nothing more embarrassing than not being able to get back on board! Swim platforms can make all the difference when it comes to water sports, hanging at the sand bar, or even unplanned exits.
For these reasons, we designed a set of platforms the average boat owner can buy and install on their own. Adding a swim platform and ladder to an outboard or I/O-powered boat is well within the abilities of the average do-it-yourselfer, but it does require some careful forethought and planning. Here are a few important considerations:
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How Wide Is Your Mounting Area?
Both the width and height of the area on your transom where you plan to mount the platform are important. For starters, you obviously need enough width on the transom itself to fit the platform — generally 18” to 20”. But, with an outboard boat, you also need clearance for your engine(s) to turn fully without contacting the aft corner of the platform or a grab rail.
Outboard-specific ladders like our popular Outboard Swim Platform with 2 Step Ladder, which have only one grab rail on the outboard side of the platform, offer more clearance for engines. There are two trade-offs, though. First, without the second grab rail, the platform has to be supported by a strut underneath, which requires a significantly taller mounting surface. Second, platforms with two grab rails are just easier to climb out of the water on.
The bottom line is that a platform with two grab rails is a better choice unless you absolutely can’t fit it because of engine clearance issues or the shape of your transom. Platforms with two grab rails are commonly marketed as being for I/O-powered boats, but will in fact fit many larger outboard boats.
How Tall Is Your Mounting Area?
In terms of height, the important measurement is inside your transom, not outside. The upper end of the grab rail(s) must be through-bolted to the transom, so you have to be able to reach the back of the upper fasteners from inside. Make sure you have enough clearance around these bolts for fender washers or backing plates.
Outboard-specific models with one grab rail and a bottom support typically require around 24” of height from the top fastener to the bottom fastener. Inboard-outboard models like our Inboard Outboard 3 Step Ladder with two grab rails and no bottom support typically require about 15”.
Finally, remember that you don’t simply need a certain amount of height on your transom to mount a platform. You have to take the waterline into account too. Platforms should be mounted roughly 1” above the waterline on the transom, so you’ll need to be able to bolt your grab rail(s) to the transom roughly 11” above that, depending on manufacturer and model.
How Are you Going to Use Your Platform?
What you plan to use your platform for — and how you often — will influence what length and type of ladder you choose. As a rule, the higher the bottom step of your ladder is, the harder it is to use. Add weight belts, waves and other complicating factors, and it gets even harder.
For a ladder meant to be used only on rare occasions by relatively fit adults or as an emergency boarding device, a single step is fine.
Single-step ladders also work well as an extra step when climbing aboard in shallow water — say waist deep or less — at the beach or sandbar. Getting aboard in water over your head with a single step ladder requires a good bit of leg and upper-body strength.
Two-step ladders are easier to use than single-step, but if you use a ladder a lot — or if you need it to work for people who aren’t physically fit — spring for a three-step. Aside from price, there’s no real drawback to a three-step vs. a two-step. Some three-step models have a slightly larger platform — and thus require slightly more mounting space — but if you can fit a three-step, that’s the better choice.
Finally, if you’re planning to use a ladder for scuba or serious freediving, consider a center post model. Center post ladders can be climbed with fins on and they are angled away from the boat almost like steep stairs, which makes them easier to climb in heavy dive gear.
Additional Considerations
Keep in mind that you may need to install an additional grab bar or two on the top of your transom or on your back deck. With your feet on the top step of a ladder, the platform grab rails are too low to be of much use.
Instead, you’ll need something in the boat to hold onto. A strategically placed grab bar, like our Stainless Steel Grab Handle can make all the difference in ease of boarding.
Finally, on outboard boats, platforms are most commonly mounted on the port side for the simple reason that engine hose, wiring and control cables almost always from the starboard side. Many modern outboard boats, though, have almost completely hidden engine rigging. If that’s the case, there’s not reason to not mount your platform on the starboard sid
