ST12 and ST12 Installation Instructions

Note: These installation instructions are Bennett ST12 and ST16 Sport Tab kits only. Contact Bennett Marine for installation
instructions for other Bennett Trim Tab kits. Other instructions are also available online at www.bennetttrimtabs.com/install.htm.

Tools and Materials List:
1/2" Wrench	Teflon Tape
Electric Drill	Wire Stripper
Four Foot Straightedge	1 1/8" Hole Saw
Marine Grade Sealant	Tape Measure
Vise Grips	Wire Cutters
3/16" and 1/2" Drill Bits	#2 and 3 Phillips Head Screwdriver
Wire Crimpers	Marine Epoxy
Masking Tape	1 Qt. Automatic Transmission Fluid

Step 1 - Position the tabs against the transom and check to see that the upper mounts of the hydraulic actuators do not center on an inside obstruction. If they do, reposition the tabs slightly outboard. The further outboard the tabs are mounted, the greater the lateral (side to side) control. Position tabs 3" to 4" from the chine, and a minimum of 10" from the centerline of outboard or sterndrive unit (see Figure 1). On the ST16 trim tabs, the angled sides face inboard (see Figure 2). Note: if the inside of the transom is inaccessible due to a fuel tank, flotation, or other obstruction, call Bennett Marine for alternate installation instructions at (954) 427-1400. Click here to see images of alternate mounting options.

Step 2 - Attach the mounting plates and trim plane with #14 x 1-1/2" stainless screws 3/8" above hull bottom (see Figure 3). Make 3/16" pilot holes for the mounting screws. Assemble mounting plates and tab, dip screws in marine epoxy before running in. Position trim tab between mounting plates before running screws tight. Snug screws down to secure mounting plates and trim tab to transom.

Step 3 - Secure the lower hinge of each actuator to the tab with 1/4-20 x 3/4" Phillips head machine screws. Use a straightedge to set the "negative angle" of the tab's trailing edge as shown in Figure 2. The ST16 should have a negative angle of 1-1/4", and the ST12 should be 1".

Step 4 - With tabs set at the negative angle, position the upper mounts of the actuators against the transom. Slide the actuator template behind the upper mount, align and tape to transom. It is not necessary that the upper mounts lie flat against the transom as the actuator neck has the ability to flex far more than necessary. The straightedge may now be removed. Drill holes accurately as indicated on templates. Drilling a small pilot hole first helps you to locate accurate centers.

Step 5 - Install the pipe nipples (dry) snugly into the actuator upper mounts. Do not use Teflon tape. Use care to avoid cross threading and do not over tighten. (Turn in nipple finger tight, then two full turns with vise grips. NO MORE). Apply waterproof sealant on surface around pipe nipples and screw holes. Insert pipe nipples through transom and secure actuator upper mounts to transom with #14 x 1-1/2" screws. Note: cover ends of pipe nipples with masking tape to prevent debris from entering the system. Remove masking tape before making connections inside the boat.

Step 6 - Install Hydraulic Power Unit (HPU) in a convenient location with a dry environment. Important: The HPU must be mounted in a dry enough location to avoid submersion and drenching. Allow some space above the HPU so that is may be slid into its mounting bracket (about 3"). Lay out upper holes on HPU mounting bracket 4-5/8" apart and start #10 x 1" screws using 5/32" pilot holes. Then drill 5/32" pilot holes for the lower screws and mounting bracket. Fill HPU reservoir to full line using any type of automatic transmission fluid (ATF). Slide HPU into bracket.

Step 7 - Inside the transom, apply Teflon tape on male threads of pipe nipples and tighten 90 degree brass elbows to pipe nipples. While tightening elbow, hold pipe nipple with vise grips to prevent stripping actuator upper mount threads. On the ports side tab, cut tow short runs of hydraulic tubing and attach to brass tee with "nut with ferrule fitting". These will be the lines that connect the two nipples. (To use "nut with ferrule", insert tubing through the nut and push until it bottoms in the fitting. While continuing bottom the tubing in the fitting, tighten nut "finger tight, then 1 full turn with a 1/2" wrench. No more.) Connect the two short runs of tubing from the brass tee to the two elbows using the "nut with ferrule" fittings. Connect one end of the long coil of tubing into the remaining fitting of the brass tee and run to HPU. Repeat for starboard side tab.

Step 8 - With plastic hangers secure hydraulic tubing along hullside or bulkheads to HPU. When facing HPU the brass fitting on the left of the pump face connects to the tubing from the port actuators, the fitting on the right connects with the tubing from the starboard actuators. These fittings are marked "P" and "S" for port and starboard. Connect tubing to HPU fittings as described in Step 7. Use tube bending clips at desired 90 degree bends in tubing to prevent kinking.

Step 10 - Plug connector of Interrupter Relay to HPU plug. Attach black ground wire ring terminal to either stud on the back of the HPU motor or to any convenient ground. Mount Interrupter Relay. Plug other connector to the connector of the 4-color wire harness. Run other end of wire harness to desired location of trim tab control switch. Secure wire harness with plastic hangers and cut to length. Install control switch according to "RS1000 Rocker Switch Installation Instructions".

Step 11 - Fill HPU reservoir to full line using any type of automatic transmission fluid (ATF).

Step 12 - Using the Rocker Switch Control, press the "Bow Down" position for 15 seconds, then "Bow Up" for 15-20 seconds. Repeat 3 times. This will purge any air from the system. No bleeding is necessary.

Step 13 - Place both tabs in the "full down" position and check all hydraulic connections for leaks. Bring the tabs to the full up position and check fluid level. Add ATF if necessary.

IMPORTANT NOTE FOR BOATS KEPT IN SALTWATER: The black finish of the trim tabs provides a barrier from electrolytic action. However, if the boat is kept in saltwater for long periods of time, a zinc anode must be applied to the top side of each tab. To provide protection, the zinc must make good contact with the stainless steel. Therefore the coating under the zinc must be removed. Do not ground the tabs to other underwater appendages. The black finish does not provide anti-fouling protection and should be painted with anti-fouling paint if such protection is required.