Mercury MerCruiser OEM Trim Sender & Gimbal Ring Screw 37978 | 10-37978 | #10-32 x 3/4 in. Stainless

Mercury MerCruiser OEM Trim Sender & Gimbal Ring Screw — Part 37978

• Part Number: 37978
• Full Catalog Number: 10-37978
• Brand: Mercury Marine / MerCruiser (Genuine OEM)
• Official Product Type: Hardware & Fasteners — #10-32 x 3/4 in. Stainless Steel Screw
• Thread: #10-32
• Length: 0.750 in. / 19.05 mm
• Material: Stainless steel
• Primary Verified Use: Securing the trim sender and trim limit switch assemblies to the gimbal ring on MerCruiser sterndrive transom assemblies
• Typical Quantity per Assembly: 4 screws per transom assembly (with 4 lockwashers 26996 and 4 retainers 57008)
• GTIN / UPC: 745061077294
• Weight: approx. 0.005 kg

Specific fastener — #10-32 x 3/4 in., stainless: 37978 / 10-37978 is the OEM screw used to mount the trim sender and trim limit switch to the gimbal ring on applicable MerCruiser sterndrive transom assemblies. The combination of #10-32 thread, 3/4 in. length, and stainless construction is specific to this application — the correct length matters for secure mounting without interfering with the sender assembly. Confirm the part number from the Mercury parts diagram for the specific drive model and serial number before ordering.

What It Is

The 37978 / 10-37978 is the genuine OEM #10-32 x 3/4 in. stainless steel screw used in MerCruiser sterndrive transom assemblies to secure the trim sender and trim limit switch to the gimbal ring. MerCruiser diagrams commonly show four 37978 screws per transom assembly, used with #10 stainless lockwashers (26996) and trim sender/switch retainers (57008). These screws are exposed to water and corrosion around the transom assembly, making stainless construction an important specification for this application. The same #10-32 x 3/4 in. stainless screw may also appear in other MerCruiser hardware positions, so the diagram location should be confirmed when ordering for an application other than trim sender/switch mounting.

Compatible Applications

Confirm the exact gimbal ring diagram and trim sender / switch arrangement for the specific MerCruiser drive model and serial number before ordering.

• MerCruiser sterndrive transom assemblies — trim sender mounting to gimbal ring — where the Mercury parts diagram specifies 37978
• MerCruiser sterndrive transom assemblies — trim limit switch mounting to gimbal ring — where the Mercury parts diagram specifies 37978
• Selected MerCruiser sterndrive families using conventional external trim sender / trim limit switch assemblies on the gimbal ring

Not sure it fits? Send us your MerCruiser sterndrive or transom assembly serial number before ordering.

Related Hardware

MerCruiser trim sender / gimbal ring diagrams show 37978 used with the following components. These are sold separately:

• 26996 — #10 stainless steel lockwasher (4 used per assembly with 37978)
• 57008 — Trim sender / switch screw retainer (4 used per assembly with 37978)
• 63990 — Switch and sender insulator
• 805320A03 — Trim and limit switch assembly (applicable drives)
• 805320A2 — Single-station trim sender kit (selected applications)
• 805130A8 — Dual-station sender kit (selected applications)

Part Numbers

• 37978 — Current Mercury / MerCruiser OEM part number
• 10-37978 — Full Mercury / Quicksilver catalog number

No superseding Mercury part number is confirmed in current OEM references for 37978.

When to Replace

Replace the screw when:

• The Phillips or drive head is damaged, stripped, or rounded
• Threads are corroded, stripped, or cross-threaded
• The screw has seized in the gimbal ring and cannot be removed cleanly
• The fastener is bent from overtightening or impact
• The original screw is missing from the sender or switch mounting
• Trim sender or trim limit switch service requires renewed mounting hardware

Because all four screws are exposed to water and corrosion in the transom assembly area, inspect all four fasteners whenever trim sender, trim limit switch, or bellows service is being performed. Replacing all four at the same service is a practical approach given the low cost relative to the labour involved.

Service Interval

No fixed interval — inspect on condition. 37978 screws are accessed during trim sender, trim limit switch, and transom/bellows service. Inspect for corrosion, thread condition, and head integrity during any transom area service. In saltwater environments, corrosion at the screw head and thread interface is the most common failure mode. Replacing all four screws (with lockwashers 26996 and retainers 57008) whenever the sender or switch assembly is removed is a sound preventive practice.

Installation Notes

• Confirm 37978 is the correct screw from the Mercury parts diagram for the specific MerCruiser drive model and serial number
• MerCruiser diagrams typically specify four 37978 screws with four 26996 lockwashers and four 57008 retainers per transom assembly — confirm the quantity from the diagram for the specific drive
• Do not overtighten the sender mounting screws — the trim sender and limit switch housings require correct positioning for adjustment, and overtightening can distort the sender housing or affect switch calibration
• Inspect the gimbal ring tapped holes for thread condition and corrosion before installing the replacement screws
• Inspect the sender insulator (63990) and switch/sender assembly for damage or wear while the hardware is removed
• Follow the applicable MerCruiser transom service manual for sender and switch installation, positioning, and adjustment procedures

Technical FAQ

Q: How many 37978 screws do I need per transom assembly?
MerCruiser diagrams commonly show four 37978 screws per transom assembly for the trim sender and limit switch installation — four screws with four 26996 lockwashers and four 57008 retainers. Confirm the quantity from the Mercury parts diagram for the specific drive model before ordering.

Q: Can I use a standard #10-32 x 3/4 in. screw from a hardware store?
The thread and length match a standard #10-32 x 3/4 in. fastener, but 37978 is specified as stainless steel for the marine transom environment. A standard hardware store screw in a non-corrosion-resistant grade will corrode and seize in the gimbal ring, making future sender service significantly more difficult. Using the OEM stainless specification is the correct approach for this application.

Q: Do I need to replace the lockwashers and retainers at the same time?
It is recommended. MerCruiser specifies stainless lockwashers (26996) and retainers (57008) with the 37978 screws. When trim sender service requires removing all four fasteners, replacing the complete hardware set — screws, lockwashers, and retainers — avoids a second disassembly if a corroded lockwasher or retainer fails shortly after.

Parts Desk Insights

The most useful detail about 37978 is its specific combination of #10-32 thread, 3/4 in. length, and stainless construction in the trim sender and gimbal ring application. Customers doing trim sender or limit switch service sometimes try to source a generic #10-32 screw locally to avoid a parts order, but the stainless specification is important in the transom environment — a non-stainless screw will corrode and seize, turning the next sender service into a much more involved job. The most common scenario for ordering 37978 is trim sender or limit switch removal where one or more screws have corroded heads or seized threads. Suggesting the full hardware set (37978 screws + 26996 lockwashers + 57008 retainers) rather than individual screws is worth doing when the assembly is already apart.