NOS vs used vs aftermarket marine parts: which should you buy?
Short answer: NOS (new-old-stock) parts are original factory parts that were never installed. Used parts came off another engine. Aftermarket parts are made by a different company to fit. NOS is usually the closest match to the original, used parts depend on their condition and testing, and aftermarket quality depends on the brand. Ask for photos, part numbers and the return terms whichever you choose.
How do they compare?
| Type | What it is | Watch for |
|---|---|---|
| NOS | Original manufacturer part, never installed, often in its original box | Age: rubber seals, gaskets and impellers can dry out on the shelf. Check the box label matches your part number or a supersession. |
| Tested used | Original part removed from another engine | Ask how it was tested and what engine it came from. Look for corrosion, especially on saltwater engines. |
| Aftermarket | Made by another company to fit your engine | Quality and fit vary by maker. Check the maker's cross-reference to your original part number. |
When is NOS worth it?
When no new part is made anymore and fit matters, for example ignition parts, shift cables or gearcase parts on older OMC, Johnson and Evinrude engines. Inspect anything rubber before installing.
When does used make sense?
For heavy, durable parts such as brackets, housings or castings, where condition is easy to judge from photos.
When does aftermarket make sense?
For common wear items from established makers, where a new aftermarket part may be easier to find than an old factory one.
What about warranties?
Ask the seller in writing what's covered and for how long. Under federal law, a written warranty on a consumer product has to be clear about what it covers.1
Common questions
What does NOS mean for boat parts?
NOS stands for new-old-stock: original manufacturer parts that were never installed, often still in the factory box.
Are NOS parts better than aftermarket?
NOS parts are original factory parts, so they usually match the original fit. Rubber parts can age on the shelf, and some aftermarket makers produce good parts. Compare part numbers, condition and return terms.
Is it safe to buy used outboard parts?
It can be, if the seller tells you what engine the part came from and how it was tested, and shows clear photos. Watch for saltwater corrosion.
Send your engine make, horsepower, year and the part you need (or a photo of the old part). The search is free, and you see a photo of the actual part before you pay anything.
Find My Part →Sources
- Federal Trade Commission, "Businessperson's Guide to Federal Warranty Law" (Magnuson-Moss Warranty Act). ftc.gov