T-H Marine Z-Lock 4" Setback Manual Single-Adjust Jack Plate

The T-H Marine Z-Lock 4" Setback Manual Single Adjust Jack Plate is the manual-adjust variant in T-H Marine's Z-Lock jack plate line - the right choice for boats that need a real heavy-duty jack plate without the cost premium and install complexity of a hydraulic plate. T-H Marine's hydraulic jack plates (ATLAS series) are the right call for owners who want to adjust prop depth underway. For owners who set their prop depth once for the day's conditions and leave it (the typical use case for tournament bass anglers who dial in the right depth for the morning and don't change it, or for owners who just want the setback advantage without the underway-adjustment feature), the Z-Lock manual plate is the cost-effective alternative.

Z-Lock design - eliminates side slippage. The Z-Lock feature is what makes this plate meaningfully better than older manual jack plate designs. Traditional manual jack plates use side plates that bolt to the upright section, with the bolts taking all the side loads when the outboard is running. Under high loads (hard cornering, big-wake hits, high-speed running), the side plates can shift slightly under bolt clearance, which over time causes loose connections, accelerated wear, and eventually plate failure. The Z-Lock design uses matching slotted extrusions on the upright and side plates that mechanically interlock - the side plates physically can't move sideways because they're constrained by the Z-shape engagement, regardless of bolt loading. The result: no side slippage, no looseness over time, and dramatically improved long-term durability.

4-inch setback. The 4-inch setback distance positions the outboard 4 inches aft of the transom face. Why setback matters: the prop sits in cleaner water aft of the hull's wake, which reduces prop ventilation, improves top speed, and improves bow lift on planing boats. 4 inches is the most popular setback for closed-bow runabouts, smaller offshore center consoles, and any boat where transom overhang space is limited. For boats with more transom clearance and where maximum performance is the goal, T-H Marine offers 6", 8", 10", and 12" setback variants of the same Z-Lock plate.

Aircraft-grade aluminum, full 1/2-inch material. The Z-Lock is built from aircraft-grade aluminum (typically 6061-T6 marine-grade) at full 1/2-inch material thickness throughout. The 1/2-inch material is meaningfully thicker than the 3/8-inch material common on cheaper manual jack plates - more strength margin under heavy outboard loads, less flex under hard acceleration, less long-term fatigue under repeated load cycles. Combined with the Z-Lock engagement, the 1/2-inch material gives this jack plate dramatically better long-term reliability than cheaper alternatives.

Handles V6 AND V8 outboards up to 300 HP. The plate is rated for V6 and V8 outboards up to 300 horsepower. Most current production outboards in the 200-300 HP range fit within these limits. Above 300 HP (the 350-400+ HP V8 and inline-6 high-output outboards now common on premium bass boats and large offshore center consoles), step up to T-H Marine's higher-capacity jack plates. The 300 HP rating covers the bulk of recreational marine outboard installations.

5 inches of vertical adjustment. The plate provides 5 inches of vertical motor position adjustment - enough range to dial in optimal prop depth for boat-specific performance characteristics. The adjustment is done at the dock (motor stopped) by loosening the side bolts, sliding the motor mounting plate up or down to the desired position, and re-tightening the bolts. Easy to adjust from the top of the jack means you don't need to be in the water behind the boat to make the adjustment - the adjustment points are accessible from above.

Manual single-adjust mechanism. The 'manual single adjust' designation means you adjust the prop depth manually (vs hydraulic actuator on the ATLAS series), with a single adjustment that sets the position for the operating session. Set it once at the dock, leave it for the day. For most recreational boating, this is the right tradeoff - hydraulic plates cost 2-3x more and are useful primarily for on-the-fly adjustments during fishing or specific operating conditions. For owners who don't need that capability, the manual plate delivers most of the setback benefit at a fraction of the cost.

27 lb weight. The plate weighs 27 lbs - lighter than the hydraulic jack plates (which include heavy hydraulic actuator) and lighter than older manual jack plates with thinner material. The lower weight is meaningful for two reasons: easier install (one person can mount the plate without help), and lower running weight on the boat (every pound of stern weight affects planing and top speed marginally).

Easy adjustment from top of jack. The adjustment bolts are accessible from the top of the jack plate - no need to crawl behind the outboard or get in the water to make the adjustment. Loosen the side bolts at the top of the plate, slide the motor mounting plate to the new position, re-tighten the bolts. Total adjustment time at the dock is 5-10 minutes for someone who knows the procedure.

Setback advantages. Even without the on-the-fly adjustment of a hydraulic plate, the 4-inch setback delivers real performance benefits: prop runs in cleaner water aft of the hull wake (less ventilation, more efficient propulsion), bow lift at planing speeds improves, top speed typically increases 2-5 mph on most boats due to better prop performance, and the boat's hole shot can be tuned by adjusting vertical position. For boats running competitive at 50+ mph, the setback advantage is real and measurable. for typical recreational use at 30-40 mph, the advantage is smaller but still meaningful.

JPZ-4-DP - the polished finish variant. The DP suffix indicates polished aluminum finish - matches well with chrome and polished aluminum trim packages on premium bass boats and offshore center consoles. T-H Marine offers the same Z-Lock plate in different finishes for owners who prefer alternatives. Polished aluminum requires occasional buffing to maintain the polished look, but the underlying aluminum is corrosion-resistant either way.

Install. Mount the plate to the transom using the supplied bolts (5/8-inch bolts through the transom skin, with backing plates inside, marine sealant at every penetration). Mount the outboard to the back of the jack plate using the standard outboard mounting bolts (longer bolts than the original transom mount, since the bolts now pass through the additional 1/2-inch plate thickness). Adjust the vertical position to the desired starting point. Tighten everything down. Total install runs 1-3 hours for someone with reasonable mechanical skills. For owners not comfortable with the install, professional install at a marine shop is straightforward.

Vs hydraulic jack plates. The Z-Lock manual plate is the cost-effective alternative to hydraulic jack plates (T-H Marine's ATLAS series). The manual plate delivers the setback benefit and the static vertical adjustment range at meaningfully lower cost and meaningfully simpler install. The hydraulic plate adds on-the-fly vertical adjustment while underway, which is useful for owners doing competitive tournament fishing or specific operational conditions where the right prop depth changes during the day. For owners whose typical use is one prop depth for the day, the manual plate is the right call - same setback advantage, none of the hydraulic plumbing or electrical install complexity.

Warranty. Standard T-H Marine warranty terms apply against manufacturing defects under normal recreational use. Save the receipt and original packaging if practical for warranty service. The Z-Lock design's mechanical engagement makes long-term failure significantly less likely than older manual jack plate designs - the warranty rarely gets exercised in real-world use.