BOW THRUSTER

PROCEDURE FOR 8" TUNNEL INSTALLATION

PLEASE READ ALL INSTRUCTIONS BEFORE STARTING INSTALLATION

FIRST STEP

We recommend positioning the tunnel as far forward and as low as possible, maintaining approximately 6" minimum between the waterline and the top of the tunnel. Locate the position of the tunnel centerline on hull. Rotate the tunnel to provide convenient future access to the hydraulic motor. Be sure to allow enough space for removal of hydraulic assembly for service and maintenance. Please remember that the splined shaft on the motor is approximately 1 1/4" long. To remove the assembly, about 2 or 3 inches minimum clearance should be maintained near bulkheads or other obstructions.

Note: the following steps apply to fiberglass hulls only:

Stiffeners should be applied to the tunnel if length of tube exceeds standard tunnel lengths (3 ft. for 6 in. unit). Structural foam stiffeners shold be applied to tunnel lengthwise with Epoxy West System and encapsulated in glass. A minimum of two locations, one on each side of thruster assembly, should be applied opposite each other.

Drill a 1/4" pilot hole on one side of the hull on the tunnel center line. Check for
clearance between the water line and the top of the tube. A 1/4" rod is then passed through the hole until it comes into contact with the other side of the hull. This rod is then leveled and aligned at right angles to the yacht's fore and aft center line from inside the hull. Where it makes contact with the hull is the location for the opposite pilot hole. Drill the next 1/4" hole from the inside of the yacht. Both full-sized holes for the tunnel can now be scribed onto the hull. These holes should be 1/8" larger than the O.D. of the tube to allow for epoxy adhesive.

SECOND STEP

Cut the scribed holes in the hull. Cut inside the scribe line, leaving a 1/8" margin, trying to keep the 1/4" blade aligned with the rod passed through the two pilot holes. Use appropriate tools to precisely enlarge the holes to the scribe line.

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 inches, 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 inches, exposing the inner side of the outer hull. The tunnel can now be epoxied and tabbed to either 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

Temporarily clamp or secure the tunnel in its correct, final position. It is essential to insure the tunnel is level and at a 90 degree angle to the boat's centerline. Using the West System, mix epoxy with silica microballoons and Cabosil Thixotropic agent. Mix a thick, creamy paste. Apply the paste to a freshly acetoned and dust-free joint between the tube and the hull on both sides (inside and outside) where the tube meets the hull. INSIDE, leave a large radius epoxy fillet to accept the glass and epoxy lay-up to follow. Make sure to grind all hull and tunnel surfaces to be bonded, prior to acetone treatment. Original hull and tunnel surfaces should be abraded to remove shiny surface. This is crucial for proper bonding.

Note for metal hulls: Proceed to welding after reading metal tunnel instructions below.

FOURTH STEP

You may now scribe a line around the excess tube on either side of the hull. Cut the tunnel on each end so as to produce a flush fit with the hull. A reciprocating hand saw with a carbide blade is effective. Always cut so as to leave material to hand rasp a final fit.

FIFTH 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 10" onto hull and 6" minimum onto tunnel around the entire tunnel. A minimum of 10 layers of woven roving saturated in the epoxy mixture can be used to secure the tunnel. Fair the layup if desired for visual appeal. Stiffeners should be applied to the tunnel if length of tunnel exceeds standard tunnel lengths (3' for 6" unit). Structural foam stiffeners should be applied to tube lengthwise with West System epoxy and encapsulated in glass. A minimum of two locations, one on each side of thruster assembly, should be applied opposite each other.

SIXTH STEP

Finish fairing exterior joints with epoxy mixture.

It is recommended that anti-fouling 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. Rotate the tunnel to locate the hydraulics 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 in position prior to drilling the next hole. Next remove the saddle and square the holes carefully to receive the 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.