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Poseidon Seat Column Assembly Installation

TACO Marine Helm ChairAtlantic Seat
Z99-1230WHA TACO Marine Seat PedestalFigure 1 Seat Pedestal HoleFigure 2 TACO Marine Seat Pedestal BaseFigure 3 TACO Marine Seat SlideFigure 4

Both the Powermatic and Fixed seat column assemblies come completely assembled and ready to be attached to the deck. The seat slide assembly has mounting slots to bolt it to the seat and comes with four stainless steel hex head X 5/16 X 1 cap bolts with stainless steel washers.


  • Lead pencil
  • Electric or battery powered drill
  • 3/8 Drill Bit
  • 5/16 T-nuts
  1. You should have access to the underside of the deck where you are going to mount the seat column. If you have access to this area through a hatch you do not need to drill an access hole. You then have the option of using a backing plate, which you can make from Marine Lumber or a piece of 1/4 anodized aluminum plate. If you do not have access, drill about a 4 hole in the deck directly under the center of the column to access the 6 mounting holes. The hole should be large enough for you to reach in and install locking T-nuts under each mounting hole (Figure 2). Or make 3 strips from Marine Lumber 2 x 8 and drill 2 holes 5-5/16 apart. Each will span 2 holes.

    Caution: Before drilling holes in the deck, make certain there are no electrical wires, gas lines or gas tank directly below the area. TACO Marinerecommends the use of Z100-1169 deck mounting base

  2. Once you know the thickness of the deck and backing plate, together with the thickness of the nuts you are going to use, you can purchase the six 5/16 stainless steel flat head machine screws, stainless steel washers and stainless steel locking T-nuts that you will use to secure the seat base to the deck. These are not provided since the length will be different for each installation. If you are using a metal backing plate replace the T-nuts with locknuts.

  3. TACO Marine recommends using a backing plate or a deck plate to insure the utmost stability in your mount. Using the seat base as a template, make sure the seat is facing in the right direction and mark all six hole locations (Figure 1), and using the recommended drill bit for your T-nuts, drill the clearance holes for the mounting screws. If you are going to use a deck plate, use the holes in the deck plate as a template to mark and drill the mounting holes.

  4. To set the T-nuts in place, install a machine screw with a washer through one of the holes in the deck. Through the access hole, place the T-nut on the screw and tighten the screw until the teeth of the T-nut dig into the underside of the Marine Lumber backing plate or strips (Figure 2), then remove the screw. Repeat until all six T-nuts are set in place.

  5. Place the column so that the base holes line up with the holes in the deck and install the six mounting screws without the washers, into the six T-nuts, placing some anti-seize under the head of each screw before tightening. If you are using a deck plate, install the screws through the deck plate into the T-nuts and use the machine screws that come with the deck plate to attach the seat pedestal to the deck plate. If you are using a full backing plate underneath the deck, install the backing plate onto the screws coming through the deck. While someone holds the locknuts with a wrench, tighten the screws or vice versa (Figure 3).

  6. Move the seat slide all the way forward and using two of the four hex head cap bolts and install them into the seat (Figure 4). Move the seat slide all the way back and do the same with the other two hex head cap bolts to complete the seat installation. If you do not have a Zwaardvis seat, you may have to use different bolts and nuts to install your seat.