Our 17" diameter floats are often used to add flotation to other brands of pontoon boats with 20" and small diameter floats. We do not offer a mounting kit for our 17" diameter floats to accomplish the installation, but the parts you'll need are easy to obtain and installation is fairly simple. Here we have provided general instructions for mounting this third row of floats under your existing boat. Please bear in mind that pontoon boat frames are greatly different from one brand to another, but even if your frame is different than the example boat frames that we show in these instuctions, the general concept of how to make it all happen is very similar. Boats have different types of cross members, so we have attempted to tackle the most commond frame types in our instructions. If your boat kit is different than we depict here, please call us if additional installation advice is required. We will not build a specific set of instructions for your application as our instructions take a large amount of time to build, but we are happy to have a conversation and provide verbal advice concerning your specific installation.

To help with your installation, we have provided a list of the required tools and aluminum mounting tube for your installation. Links are also provided to the required hardware and aluminum tube, but please bear in mind that the bolt length we list below for attaching the mounting tube to 1/8"-1/4" thick hat channel, C-channel, or Z-bar type cross members. If you have a tube cross member, you will have to bolt straight through the cross member and the deck above. Length of the required bolts will be dependant on the total thickness of the floor structure. Contact us for recommendations on hardware if you do not have channel or Z-bar cross-members.

23/64" transfer punch McMaster PN: 3374A31
Center punch (optional) McMaster PN: 3451A31
3/8" drive ratchet
9/16", 3/8" drive socket
3/8" drive ratchet extension
9/16" box wrench
Electric drill
3/8" drill bit McMaster PN: 8870A36
3/8" extra-long drill bit McMaster PN: 2939A28
7/8" max-dia step drill bit Link to Amazon search
3/4" countersink (optional) McMaster PN: 2846A39
Carpenter square
Tape measure
2 saw horses
2 C or F style clamps
2-4 ratchet straps
Steel hammer
Ruber or plastic hammer (optional)
3/8" x 4 1/2" SS hex bolt
-2 per float
McMaster PN: 92198A642
3/8" x 1" SS fender washer
-4 per float
McMaster PN: 92141A051
3/8" SS lock nut
-2 per float
McMaster PN: 91831A127
Blue medium strength Loctite capsule
-1 capsule per 3 floats
McMaster PN: 91458A111
3"x1.5", 1/8" thick aluminum tube
-length varies by application
Link to tube from Online Metals
3/8" x 1 1/4" SS hex bolts
-for channel cross members
-qty. varies by application
McMaster PN: 92240A626
3/8" SAE SS washer
-for channel cross members
-qty. varies by application
McMaster PN: 96659A108
3/8" SS flanged lock nut
-qty. varies by application
McMaster PN: 94238A103


To the right we have an example of a 16' pontoon boat that has C-channel cross-members. For this example, we will be installing a full run of 17" diameter floats. This will require use of a length of 3"x1 1/2" aluminum tube with a 1/8" thick wall. At the top of this page, we have provided a link to a trusted supplier for this length of tube. Many customers will be able to get this tube from a local supplier as well. You will have to measure your cross members and verify what length tube you will require to both bolt onto the cross-members on your boat and be long enough to bolt the floats to. If you need advice concerning the required length for the floats themselves, please contact us.


With the length of aluminum tube cut to the appropriate length, center it under your boat and clamp it into place. Depending on the design of your boat, this may be a little tricky or require a helper. With a permanent marker, mark the location of each cross member on your boat that the piece of aluminum crosses. This will allow you to center the mounting holes you need to drill next. Also, write the words "FRONT" and "REAR" on the ends of the tube to indicate which way the tube points on the boat. This is very important.


Remove the aluminum tube from under your boat. Use a center punch to mark the position you have to drill centered between each pair of lines that you drew on the aluminum tube indicating the location of your cross members. Use a 3/8" drill bit to drill straight through the top and bottom holes of the aluminum tube. This is MUCH easier to do on a drill press, but it can be done with a hand drill. If you're using a hand drill be super careful to make sure that your drill bit stays straight when you drill through the second wall of the tube.

On the bottom of the tube (side of tube opposite where you drew the lines), drill the 3/8" holes out to 7/8" diameter holes. We recommend using a step drill bit for this. This type of drill self-centers and is an inexpensive tool that can be found on eBay or Amazon for just a few dollars. The side of the tube with the 3/8" diameter holes and drawn lines is from here forward going to be called the "top of the tube". The holes in the top of the tube remain at the 3/8" diameter.

After drilling the holes, be sure to debur the holes. We like to use a countersink type drill bit for this, but a little bit of sand paper will do the trick as well.


Using two "C" or "F" type clamps, clamp the aluminum tube across two saw horses. Have the top of the tube facing downward so that the 7/8" diameter holes are facing up as shown.


Place the first of the straight floats (blunt end) on the end of the aluminum tube that you labeled "REAR". Put the button end of the floats facing the far end of the aluminum tube, as shown below. Tap the float into position so that the end of the float is even with the rear end of the aluminum tube. Install a ratchet strap around the float and around the aluminum tube and tighten the strap. Verify that the float is still even with the end of the tube. If you need you adjust the position, use a rubber or plastic mallet to tap it into position.


Place the remaining straight floats onto the aluminum tube and tap them against the rear float you installed in the last step. Install ratchet straps around all the floats you just placed on the aluminum tube and verify that the rearmost float is still even with the end of the aluminum tube. Place the nose cone on the front of the aluminum tube and just double check that the nose cone is on the end of the tube labeled "FRONT".


Using your 23/64" transfer punch, go down both sides of the pontoon assembly and use the punch with a hammer to mark EVERY bolt hole position through the molded-in bolt holes in the floats. The ratchet straps will hold the straight floats in position for this, but the nose cones will have to be heald in position when you do this. The nose cones don't typically fit the aluminum tube as tightly as the straight floats, so be sure that you line up the circular portion of the floats before marking the holes with your transfer punch.


Remove the ratchet straps. Before removing the floats, number the positions of the floats on the aluminum tube as shown here. You can use a piece of masking tape to write on or you can use a marker to write on the floats and aluminum tube. Lacquer thinner will remove permanent marker from the aluminum and the floats without hurting either. Otherwise, just write the numbers in a position that gets hidden when the floats are installed. Remove the floats and unclamp the aluminum tube from your saw horses.


Use your center punch to make the marks you made with the center punch in step 7 more pronounce. This will make the holes easier to drill in the next step.


Now you need to drill holes where you marked with your punch. Using a SHARP (prohibits wandering of the bit) 3/8" diameter drill bit, drill through ONE WALL of the aluminum tube from each marked position. This means that you are NOT drilling all the way through both sides of the tube at once during this operation. Drill through every position on one side of the part, flip it, and drill through every position on the other side of the part.

After drilling the holes, be sure to debur the holes. We like to use a countersink type drill bit for this, but a little bit of sand paper will do the trick as well.


Clamp the aluminum tube back onto your saw horses and place the floats back onto the tube, matching up the numbers you marked in step 8. Place the ratchet straps back over the floats and tap the floats into position so that the holes line up. DO NOT INSERT THE BOLTS YET.


With a 3/8" drill bit mounted in your hand-heald drill, start at the back end of the run of floats and drill through the rear-most bolt hole in the float. This operation makes sure that no chips are in the way and ensures that the holes are perfectly aligned. After drilling through that one bolt location, insert one of the 3/8"x4 1/2" hex bolts with a 1" outside diameter fender washer over it, and tap it through the hole with a hammer. We prefer to use a plastic hammer for this. Drill through the next hole and insert a bolt. Do this until every floats has bolts installed in both holes. DO NOT INSTALL THE NUTS YET.


Remove all the bolts and ratchet straps and remove all the floats from the aluminum tube. Place the floats aside and unclamp the tube from the saw horses.


Clamp the aluminum tube back under your boat and be sure that the "FRONT" and "REAR" labels on the tube are pointing in the correct direction on your boat. Line up the lines you drew with the cross members, make certain that the tube is centered on you frame (left to right), and double check your placement with a carpenter's square to ensure that the tube is square with the cross members. Double-check the placement as you can't undrill the holes you have to drill in the next step.


Using your 3/8" drill bit, drill up through the holes you drilled in the aluminum tube and drill through the cross-members on your boat. If you have C-channel, hat channel, or Z-bar cross-member, you are just drilling through the bottom wall of that cross member. If you have a tube cross member, or any other type of cross member that doesn't allow access to install a bolt, you will have to drill ALL THE WAY through each cross member and through the floor of the boat. If you have to drill all the way throught the floor, you will require an "extra-long" drill bit to do this. A link to that drill bit is listed in the table at the top of this page.


If your boat has hat channel, C-channel, or Z-bar cross-members (up to 1/4" thick), install a 3/8" x 1 1/4" bolt with a lock-washer and SAE flat washer through the hole you just drilled so that the bolt hangs down into the aluminum tube.

If you have the scenario where you have to drill all the way through the floor, you will want to use stainless carriage bolts. The length of the bolt will depend on the combined thickness of your floor structure. If bolting straight through the deck, tap the bolt through the hole and give it a single solid hit on the head with a hammer to start to drive it into the floor surface.

For either scenario, install a 3/8" flanged lock nut onto the bolt. The large 7/8" diameter holes allow you to put the lock nut into a socket (flange allows it to sit on the end of the socket) with a drive extension and reach in to the bolts protruding into the tube. Tighten all the nuts and bolts holding the tube in place. If you are bolting all the way through your deck, tighten the bolts until the head of the bolt is sunken slightly into your deck surface.

Remove the clamps


Referencing the numbers that you drew on the aluminum tube and the floats, place the rearmost float onto the aluminum tube. Either a helper or a ratchet strap may be required to easily hold the float into place. Drive a 3/8" x 4 1/2" bolt with a 3/8" x 1" fender washer through the bolt holes. Wipe any chips off the protruding bolt threads with a rag and place another fender washer over the threads. Apply a little bit of medium strength Loctite to the threads. The thread locker ensures that the nut stays in place and lubricates the threads. Thread 3/8" lock nuts onto each of the bolts and tighten the nuts just until the mounting flanges on the pontoons start to flex inward. We do not have a torque specification beyond this. If you used a ratchet strap to hold the float, remove it.


Repeat step 17 and install the next float forward until all of the straight floats are installed on the aluminum tube. Bolt the nose cone on the same way.


You have now completed the installation of your third pontoon. You did a great job and it's time to get back out on the water.