Sea-Dog 5021591 Lower Unit Gear Lube Pump Adapter – 8mm-1.25 Thread (Yamaha Fit)
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Sea-Dog 5021591 Lower Unit Gear Lube Pump Adapter – 8mm-1.25 Thread
A nylon and aluminum adapter that extends the compatibility of the Sea-Dog Lower Unit Standard Pump to outboard engines with an 8mm-1.25 threaded gear lube fill port. Designed to thread directly into the lower unit drain/fill plug opening, this adapter connects to the standard pump’s flexible hose for clean, controlled gear lube changes without spills or mess.
The 8mm-1.25 thread pitch is the standard fitting for most Japanese-origin outboard engines, making this adapter an essential companion for servicing Yamaha, Nissan, Tohatsu, Honda, and Japanese-built Mercury outboards. The flexible hose on the pump allows access to fill ports in tight or awkward positions on the lower unit.
Compatibility
- 8mm-1.25 thread (this adapter): Yamaha, Nissan, Tohatsu, Honda, Mercury (Japanese origin models)
- 3/8"-16 thread (standard pump fitting, included on pump): MerCruiser, OMC, Evinrude, Johnson, Honda (70 hp & up), Volvo, Force, Mercury (US origin models), Gamefisher
Specifications
- Part Number: 5021591
- Thread pitch: 8mm-1.25
- Material: Nylon / aluminum
- Compatible pump: Sea-Dog 502150H1 Lower Unit Standard Pump
Parts Desk Insights
Best use case: This adapter is the missing piece for boaters who own the Sea-Dog 502150H1 Lower Unit Standard Pump and need to service a Yamaha or other Japanese-origin outboard. The standard pump ships with a 3/8"-16 fitting that covers most US-origin engines — this adapter adds the 8mm-1.25 thread needed for the Japanese-origin engine lineup. If you’re servicing a mixed fleet of US and Japanese-origin outboards, keeping both fittings on hand means one pump covers all your lower units. Order the pump and adapter together to have a complete gear lube change kit ready to go.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.