Extend your Mercury outboard from a 15" short shaft to a 20" long shaft with this premium Bay Manufacturing 5-inch Extension Kit. Designed for precision fit and long-lasting performance, each kit includes all components required to properly extend the driveshaft housing, water tube, and shift linkage.
This conversion kit is engineered to match OEM specifications and uses stainless steel shafts and studs for maximum corrosion resistance. Spacer housings are made from the same alloy series used in Mercury outboards, ensuring exceptional strength and durability.
Product Features
- Adds 5 inches to your motor
- Includes 5" housing, stub driveshaft, shift shaft, water tube, and all required studs, nuts, and bushing
- Manufactured with marine-grade stainless steel components
- Spacer housing available in black painted or sandblasted unpainted finish
- Direct fit for select Mercury 18–25 HP 2-Stroke outboards
- Includes 1-year manufacturer warranty
Motor Compatibility Requirements
Your motor must match the exact specifications below to ensure proper fitment.
Option 1 – Serial Number Match
-
18 HP 2-Stroke
- Fits serial numbers 6416713 and Up
Option 2 – Model & Shaft Requirements
-
20 HP 2-Stroke
- Must have 3 holes in the shift shaft
-
25 HP 2-Stroke
Must have 10 mm studs and dowel pins - Must have 3 holes in the shift shaft
Compatible Serial Numbers
- 6416713 and Up
- G044027 and Up
- B238464 and Up
- 1B207251 and Up
Included in the Kit
- (1) 5″ extension housing
- (1) 5″ drive shaft
- (1) 5″ shift shaft
- (1) 5″ water tube
- (3) studs and nuts
- (1) bushing
Paint Color
- Unpainted sandblasted finish (may vary depending on production batch)
- Can be painted to match your motor
Additional Information
This extension kit is designed specifically for the above Mercury outboard specifications. Kits are not returnable except in cases of verified warranty claims—please verify compatibility before purchasing.
Shipping Information
Additional shipping fees to Alaska, Hawaii, U.S. Territories, or international destinations will be calculated after checkout.
A PayPal request will be emailed for any additional charges.
(Some items may be excluded from international shipping.)
Customer Support
For questions or to confirm compatibility, please email customerservice@marinepartswarehouse.com
Please include your engine model or serial number to help confirm proper fitment before ordering.
