Upgrade your Mercury outboard for improved performance and water handling with this premium Bay Manufacturing 5" Extension Kit, designed for select 70–115 HP 2-stroke engines. This kit increases your motor’s shaft length by a true 5 inches, enhancing stability, control, and propeller efficiency—ideal for boats operating in deeper or rougher water.
Each Mercury extension kit includes stainless-steel shafts and studs, and the spacer housing is cast from the same high-grade alloy used in OEM production for long-term durability and superior corrosion resistance.
Product Features
- Adds 5 inches of additional shaft length
- Fits select 70 HP, 80 HP, 90 HP, 100 HP, and 115 HP Mercury 2-Stroke outboards
- Heavy-duty cast spacer housing (unpainted sandblasted finish)
- Marine-grade stainless-steel shafts and hardware
- Direct bolt-on installation
- 1-year manufacturer warranty included
- Designed and built by Bay Manufacturing, the industry leader in extension kits
Compatibility Requirements
Your outboard MUST meet the exact specifications below to use Kit 410:
Compatible Engine Models & Serial Ranges
| HP | Stroke | Cylinders | Serial Range |
|---|---|---|---|
| 70 | 2-Stroke | 3 Cylinder | A996142 & Up |
| 80 | 2-Stroke | 3 Cylinder | A996142 & Up |
| 90 | 2-Stroke | 3 Cylinder | A996142 – D283221 |
| 100 | 2-Stroke | 4 Cylinder | B209468 – D283221 |
| 115 | 2-Stroke | 4 Cylinder | B209468 – D283221 (Does NOT fit inline 6) |
Additional Notes
- Does NOT fit 115 HP inline-6 models.
- Must match both horsepower AND serial number ranges for proper fitment.
Parts Included
- (1) 5" Extension Housing
- (1) 5" Driveshaft
- (1) 5" Shift Shaft
- (1) 5" Water Tube
- (5) Studs & Nuts
- (1) Water Sleeve
- (1) Dowel Pin
- (1) Hollow Pin
Additional Information
- Newer kits may arrive black-painted; others ship unpainted with a sandblasted finish.
- Designed for OEM-level fit and long service life.
- Not returnable except for warranty claim.
Shipping Information
Additional shipping fees to Alaska, Hawaii, U.S. Territories, or international destinations will be calculated after checkout.
A PayPal request will be sent for any required surcharge.
(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.
