STERN THRUSTER

PROCEDURE FOR 8" TUNNEL INSTALLATION

PLEASE READ ALL INSTRUCTIONS BEFORE STARTING INSTALLATION

FIRST STEP

A. We recommend positioning the TUNNEL AT THE TRANSOM CENTER and as low as possible, maintaining approximately 8"-12" minimum between the waterline and the top of the tunnel DEPENDING ON HP rating of the system. 15 HP would require only 8" and 50 HP would require 12" minimum. Rotate the tunnel to provide access to the hydraulic motor through the transom. Be sure to allow enough space for removal of hydraulic assembly for service and maintenance. It is necessary to remember that the splined shaft on the motor is approximately 1 1/4" long. To remove the assembly, about 2" or 3" minimum clearance should be maintained near bulkheads or other obstruction.

SECOND STEP

Cut the rectangular access hole through the transom. This should be larger enough to allow the thruster to be removed from the tunnel through the hole in the saddle. Allowing approximately 1 inch of clearance around the Thruster flange will normally be required. SPECIAL NOTE FOR CORED HULLS:

Special care should be taken when preparing a cored hull layup. Because the core material is susceptible to wicking any moisture that might come in contact with it, proper sealing of the core material and the thruster tunnel is important. Following the above procedures, additional steps must be taken with a cored hull:

After the basic hole is cut, it is necessary to cut back the outer hull laminate 5"or 6", exposing the inner hull. The installer may also tab the tunnel to the outer hull from inside the boat. Using this procedure, the inner hull is cut back an additional 5" or 6", exposing the inner side of the outer hull or to the outside of the inner hull. Using either method, the installer should follow the tabbing procedure in steps three and four below. Install a layer of epoxy resin and microballoons in the hole between hulls making sure the core material is sealed. Continue with the installation and fairing outside of the hull for a clean, finished look.

THIRD STEP

Using the West System, mix epoxy with silica microballoons and Cabosil Thixotropic agent. Mix a thick paste. Apply the paste to a freshly acetoned and dust-free joint between the tunnel and the transom. Make sure to grind all hull and tunnel surfaces to be bonded, prior to acetone treatment. Original hull and tunnel surfaces should be penetrated beyond the shiny surface. This is crucial for proper bonding. The transom should blend into the tunnel gradually above and below.

FOURTH STEP

Allow epoxy, in prior step, to set overnight in minimum ambient temperature of 65° Fahrenheit. Sand and clean with acetone prior to work. Proceed to apply a layup of woven roving and an epoxy mixture as follows: Woven roving should extend a minimum of 10" onto hull and onto the entire tunnel. Layers of glass cloth saturated in the epoxy mixture can be used to fair the layup. The tunnel should become an integral part of the hull structure.

FIFTH STEP

It is recommended that antifouling paint be applied to all components inside the tunnel as well as the tunnel itself. The Petit Trinidad System is recommended.

FINAL STEP

Disassemble the thruster assembly, separating the saddle and props from the gearbox. The propellers are removed by unfastening the prop nuts and zincs from the prop shafts. Be sure to use Locktite #242 to resecure the zincs upon final installation and torque these with a plumbers basin wrench. The saddle is removed by unfastening the 12 1/4 x 20 hex cap screws on the top flange of the gearbox and the 3/8 nuts on the long ends of the flange.

The saddle is now used as a template to machine the thruster interface into the tunnel. Locate the template for the space available and keep in mind future possible removal for service or maintenance. The motor has a splined shaft approximately 1 1/4" long. Allow 2 to 3 inches clearance near  bulkheads, decks, or other obstructions. The hydraulic motor should be positioned from horizontal to vertical with the case drain as high as possible. Place the saddle on the tunnel in the location you wish to mount the thruster and scribe the large center hole into the tunnel. Cut this hole and again place the saddle on the tunnel over the hole. Clamp the saddle from the long end through the large hole to the tunnel. Carefully drill the 4 holes that mount the saddle, placing a bolt into each hole and securing it with a nut, to additionally secure the saddle and square the holes carefully to receive the 316SS carriage bolts. It is essential to maintain the original hole position so the saddle will be centered and axially aligned with the tunnel. If this is not done accurately the props could rub the tunnel.

Prepare the saddle interface surface by grinding the tunnel to remove the resin shine. Prepare the saddle by cleaning it with a solvent. Fit the two together without sealant and confirm that all fasteners can be tightened to full torque. 35 lb-ft for the 3/8 and 25 lb-ft for the 5/16 fasteners. If all is well, disassemble and apply 3M 5200 or other sealant such as polysulfide to both surfaces and reassamble. Fair or remove excess sealant. Carefully clean the 3/8 carriage bolts as they emerge from the top of the saddle to allow clean thread for the next nut. Let assembly cure for 24 hours.

The gearbox can now be installed in the tunnel. Clean the saddle and gearbox. This is a good time to apply anti-foul paint to the gearbox. Place the o-ring in the saddle. Place the gearbox through the hole in the saddle. Start all the 1/4" fasteners. Place the 3/8 nuts and lock washers on the end of the carriage bolts. Tighten down on the fasteners evenly. Torque each fastener at least twice.

Install props and zincs. Insure that Locktite 242 is used on the zinc threads, and torque with plumbers basin wrench. Torque prop nuts to 50 lb-ft.

Install stator screens per drawing recommendations.