Trim Cylinder Service Kit – Fits MerCruiser Pre-Alpha Drives (Replaces 45523, 45706A4, 77442A1, 77443)

$233.99

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Worry-free returns

You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

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Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This Trim Cylinder Service Kit – Fits MerCruiser Pre-Alpha Drives (Replaces 45523, 45706A4, 77442A1, 77443) is designed for MerCruiser Pre-Alpha drives from 1977–1982, specifically models ranging from 120 HP to 898 HP equipped with 2-line hydraulic systems. It serves as a comprehensive service solution for #1 and R drives where the two hydraulic lines are positioned close to the boat.

This kit provides a direct interchange for MerCruiser part numbers 45523, 45706A4, 77442A1, and 77443, as well as GLM 21990.

Engineered for direct-fit installation.
Compatible with original 2-line hydraulic systems.
Constructed from durable, marine-grade metal to withstand harsh saltwater environments.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.

Brand	Part Number
MerCruiser	45523
MerCruiser	45706A4
MerCruiser	77442A1
MerCruiser	77443
GLM	21990

Engine & Model Compatibility

Confirm your engine model and year in the table below.

This kit is specifically for MerCruiser Pre-Alpha #1/R drives with the 2-line hydraulic system common from 1977 to 1982.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
MerCruiser	Pre-Alpha #1/R Drive	120	4-Stroke	1977–1982	45523/45706A4/77442A1/77443	2-line hydraulic system
MerCruiser	Pre-Alpha #1/R Drive	140	4-Stroke	1977–1982	45523/45706A4/77442A1/77443	2-line hydraulic system
MerCruiser	Pre-Alpha #1/R Drive	165	4-Stroke	1977–1982	45523/45706A4/77442A1/77443	2-line hydraulic system
MerCruiser	Pre-Alpha #1/R Drive	228	4-Stroke	1977–1982	45523/45706A4/77442A1/77443	2-line hydraulic system
MerCruiser	Pre-Alpha #1/R Drive	250	4-Stroke	1977–1982	45523/45706A4/77442A1/77443	2-line hydraulic system
MerCruiser	Pre-Alpha #1/R Drive	485	4-Stroke	1977–1982	45523/45706A4/77442A1/77443	2-line hydraulic system
MerCruiser	Pre-Alpha #1/R Drive	898	4-Stroke	1977–1982	45523/45706A4/77442A1/77443	2-line hydraulic system

Technical Specs

Product Type: Power Trim Cylinder Service Kit
Installation: Direct replacement
Connection: 2-line hydraulic system
Housing Material: Marine-grade metal
Dimensions: Length: 40.5 cm (15.9 in), Width: 5.0 cm (2.0 in), Height: 6.0 cm (2.4 in)
Weight: 0.95 kg (2.1 lb)
Warranty: 1 year (with core return)
Other Technical Attributes: For #1 and R drives with two hydraulic lines close to the boat

What’s in the Box

1 x Power Trim Cylinder Housing (Replaces 77442A1)
1 x Bearing (Replaces 45726)
1 x O-ring Kit (Replaces 25-60342A2)

Installation Notes

Disconnect the vessel's battery to prevent electrical hazards.
Tilt the outdrive to a position that provides clear access to the trim cylinders and hydraulic lines.
Place a drip pan under the work area to catch any hydraulic fluid.
Carefully disconnect the two hydraulic lines from the cylinder, noting their positions. Plug or cap the lines to prevent contamination.
Remove the mounting pins or bolts securing the old cylinder to the drive and transom assembly.
Remove the old cylinder. Clean the mounting points and surrounding area.
Position the new cylinder and secure it with the original mounting hardware.
Reconnect the hydraulic lines to the correct ports on the new cylinder.
Refill the power trim pump reservoir with the manufacturer-recommended hydraulic fluid.
Bleed the system by cycling the trim up and down several times until operation is smooth and air-free.
Check all connections for leaks and top off the fluid reservoir as needed.
Reconnect the battery and test the full range of motion.

Troubleshooting & FAQ

How do I know if this kit fits my drive?

This kit is specifically for MerCruiser Pre-Alpha #1 and R drives made between 1977 and 1982. The key identifier is the 2-line hydraulic system where lines are close to the boat. Please verify your drive model and year and visually inspect your current cylinder setup before ordering.

What are common signs my trim cylinder needs replacement?

Symptoms include visible hydraulic fluid leaks around the cylinder body or seals, a "spongy" or jerky trim operation, the drive failing to hold its position (drifting down), or slow response when using the trim controls. These often indicate worn internal seals or a-damaged housing.

Is this a complete kit, or will I need other parts?

This is a service kit containing the cylinder housing, a bearing, and an O-ring kit, which are the core components needed for the repair. You will reuse your existing mounting hardware and hydraulic lines/fittings. Always check your specific application in case additional unique components are needed.

How do I bleed the hydraulic system after installation?

With the reservoir filled, cycle the trim system fully up and down 5-10 times. This purges air from the lines and cylinders. The operation should become smooth. Keep the reservoir topped off during the process, as the fluid level will drop as air is expelled.

What is required for the 1-year warranty core return?

The 1-year warranty requires the return of your old, original trim cylinder (the "core"). This practice allows for remanufacturing and helps keep costs down. Please contact our support team after your installation for instructions on how to process the core return.

What is the difference between OEM and this aftermarket part?

This listing is an aftermarket replacement, not an original equipment manufacturer (OEM) component. It has been engineered to meet or exceed OEM-level specifications using comparable high-quality, corrosion-resistant materials. All parts are made in an ISO 9002 certified facility and are batch-inspected to ensure quality and consistency.

How much is shipping and how fast will I get it?

We ship worldwide, and typical transit time is 5–15 days. Standard shipping is free for most regions. If available for your location, expedited shipping options and their costs will be presented at checkout.

What is your warranty and return policy?

This product is covered by a 1-year warranty against manufacturing defects under normal marine use. If you encounter any issues, please contact our support team with your order details. Returns are accepted for unused items in their original condition within our standard return window. For full details or to initiate a return, please see our policy page or contact us for instructions.

Safety & Important Info

Verify images and specifications against your original part before purchase. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement part, not an OEM component.
Professional installation is highly recommended for safety and optimal performance.

About Sea Sierra

Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
Fast Global Fulfillment — We offer free standard delivery to most regions, with parts typically arriving in 5–15 days.
Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.

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