The Bay Manufacturing 805 outboard extension kit is designed to add 5 inches to the shaft length of select Yamaha 200-300 HP outboards and Mercury 225 HP EFI models equipped with a Yamaha powerhead. The kit includes the major components needed to complete the 5-inch midsection conversion and is built with stainless steel shafts and studs for long-term marine use.
Extension Kit At a Glance
| Extension: 5 Inches | Bay Kit: 805 |
| Yamaha: Select 200-300 HP | Mercury: Select 225 HP EFI |
| Housing: Unpainted / Sandblasted | Application: Outboard Shaft Extension |
Verify Your Engine Before Ordering
Bay Manufacturing uses engine configuration, gearcase dimensions, water tube size, and other application details to determine the correct extension kit. Do not select this kit based on horsepower alone. Compare your engine to the fitment information below or contact us with your engine model and serial number before ordering.
Fitment
Yamaha Applications
- Select Yamaha 225, 250 and 300 HP outboards — 2009 and older
- Select Yamaha F250 and F300 3.3L four-stroke outboards
- Select other Yamaha 200-300 HP applications that match Bay Manufacturing's Kit 805 specifications
For applicable non-3.3L Yamaha engines, verify:
- 7 gearcase studs plus a cap bolt
- Approximately 23.5-inch gearcase length
- 5/8-inch water tube diameter
200 HP Yamaha: Additional application verification is recommended because some 200 HP models require Bay Kit 801 rather than Kit 805.
Mercury Applications
- Select Mercury 225 HP EFI outboards
- Mercury models equipped with a Yamaha powerhead
- Serial 0T and newer applications as specified by Bay Manufacturing
What's Included
- 5-inch extension housing
- Drive shaft extension
- Shift shaft extension
- Water tube extension
- 7 studs and nuts
- Cap screw
- 2 dowel pins
- Speedometer tube when required
Construction
Bay Manufacturing uses stainless steel shafts and studs in its Yamaha extension kits. The spacer housing is cast from the same series of alloy used in the original motor construction. The housing supplied with this kit has an unpainted sandblasted finish so it can be finished to match the engine.
Installation Note
On some applications, Bay Manufacturing notes that the driveshaft passageway may need to be opened with a 1-1/8-inch hole saw to provide sufficient clearance for the female end of the stub driveshaft.
Frequently Asked Questions
How much length does this kit add?
Kit 805 adds 5 inches to the outboard shaft and midsection configuration.
Does this kit fit every Yamaha 200-300 HP outboard?
No. Fitment depends on the specific engine configuration. Some applications use a different Bay Manufacturing kit, so horsepower alone should not be used to determine fitment.
What is the difference between Bay Kit 805 and 805A?
The kits cover different engine configurations. One important difference is water tube size: Kit 805 applications use a 5/8-inch water tube in the configurations listed above, while many later 805A applications use a larger water tube and different engine specifications.
Does the kit come painted?
No. The Kit 805 housing is supplied with an unpainted sandblasted finish and can be painted to match the outboard.
Does this work on a Mercury outboard?
Yes, on select Mercury 225 HP EFI models equipped with a Yamaha powerhead. Engine and serial number verification is recommended before ordering.
Questions About This Extension Kit?
Need help confirming whether Bay Kit 805 is correct for your outboard? Email us at customerservice@marinepartswarehouse.com with your engine model and serial number, and our team will be happy to help with any information we have available.
