Hydro Shield L35 and L45 installation - illustrated guide
Hydro Shield Large L35 / L45
Hydro Shield mounts on the motor's skeg below the propeller. This guide covers installation with and without power trim, using the manufacturer's dimensions and illustrations.
Estimated installation time: 20-30 minutes.
Download PDF in EnglishPackage contents
- 1 Hydro Shield hydrofoil
- 2 brackets in 316 stainless steel
- 4 stainless steel carriage bolts
- 3 stainless steel truss-head screws
- 7 Nyloc locking nuts
Tools required
- 7/16-inch spanner
- Drill and 1/4-inch drill bit (6.35 mm)
- Clamp
- Phillips screwdriver
- Tape measure
- Ruler or straightedge
- Optional: urethane sealant
1. Choose the installation type
With power trim
Use this setting when the boat has power trim and the motor is trimmed out at speed.
D = A + 1/2 inch (12.7 mm)
Minimum clearance: 1 7/8 inch (approx. 48 mm)
Between the propeller and the trailing edge of the Hydro Shield foil.
Without power trim
Use this setting when the boat has no power trim and the motor remains in a fixed position.
A = D
Minimum clearance: 1 7/8 inch (approx. 48 mm)
Between the propeller and the trailing edge of the Hydro Shield foil.
2. Attach the brackets to the foil
Attach the brackets to the foil using the carriage bolts and Nyloc nuts. Leave the nuts loose enough for the brackets to move slightly. Tighten them fully during the final tightening in step 9. Keep pressure on the carriage-bolt heads so they do not drop and damage the foil's internal locking collar.
3. Position the assembly on the skeg
Place the brackets and foil on the motor's skeg. Align the leading edges of the brackets and skeg. The brackets must not protrude beyond the leading edge of the skeg. If the skeg is bent, bend the brackets to fit without bending the skeg.
With power trim, the upper part of the bracket's front edge sits farther aft than the lower part.
4. Check alignment and clearance
Use a tape measure to check A and D. Follow the setting for your installation type below. Rotate the propeller and check the minimum clearance before drilling.
With power trim
With power trim: D must be 1/2 inch (12.7 mm) greater than A. The minimum clearance from the propeller to the foil's trailing edge is 1 7/8 inch (approx. 48 mm).
Without power trim
Without power trim: A and D must be equal. The minimum clearance from the propeller to the foil's trailing edge remains 1 7/8 inch (approx. 48 mm).
A = D
A and D must be equal.
1 7/8 inch (approx. 48 mm)
Between the propeller and the trailing edge of the Hydro Shield foil.
Rotate the propeller and check clearance.
Original manufacturer illustration; not to scale.
Extend the planing line of the L-bracket flange with a ruler or straightedge. Use this extended line when measuring A and D, as shown in the illustration.
5. Clamp the assembly in place
Once alignment and clearance are confirmed, use a clamp to hold the brackets and Hydro Shield in place.
6. Drill the first hole
Use the holes in the bracket as a template. Drill the upper rear hole first. Fit the truss-head screw and Nyloc nut.
7. Recheck the measurements and drill the remaining holes
Recheck A and D and the clearance between the propeller blade and the foil's trailing edge before drilling the second upper hole. Fit the screw and Nyloc nut. Then drill the third hole and fit the screw and nut. If using urethane sealant, apply it only after confirming the fit by fastening the screws.
8. Remove excess screw threads
If the fitted screw threads extend beyond the Nyloc nut, cut off the excess threads to prevent cavitation, reduce drag and improve performance.
9. Tighten and check
Tighten all screws and bolts securing the brackets to the skeg and foil. Check that all Nyloc nuts are tight before using the boat. Check the tightness again after the first outing.
Choose the correct model
Use the model selector in our online shop, or contact us for help before ordering.
Choose a model for your boat Download PDF in EnglishBased on Hydro Shield's 2024 installation guide. Illustrations used with permission. Inch dimensions are retained; metric clearances are approximate conversions.
Questions about installation: Nordic Smart at nordicsmart.eu or the manufacturer at hydro-shield.com.
Edition: 24 October 2026
