Sierra parts are very good high quality parts. Yes, they have a warranty, usually longer than the OEM manufacturer. Many items on a Marine engine are outsourced items, ie, the typical Stern drive engine is GM, sensors are outsourced from a supply from GM. The bolt on items such as starters and alternators are supplied from many different vendors.

Merc or volve does not manufacture these items, most are from vendors.

Sierra has some of the best u joint and shift cable bellows in the field.

several years ago Sierra rubber was junk .You could install it and in a year or two it looked like a slinky.That has been years ago ,but because of that i'm afraid of aftermarket rubber .Years after that I ran in to a Sierra rep. The rep acknowledged that Sierra "had in the past,had inferior rubber "...This was their rep telling me this ..The same rep insured me the rubber was different now..I guess the point of this post is to say if you use Sierra rubber get the current stuff...Not leftover cheap crap from way back that you may find on Ebay...I'll continue to use oem bellows because I have been bitten in the past and not willing to gamble on a product because it's a few dollars less

Over the years I've never had any issues with Sierra bellows. Mallory stuff is pretty good as well....some of it is actually a merc part in a Mallory box.

On the flip side, I've noticed differences in seal kits for drives. Especially the Sierra shift shaft seal. It's different than a merc and doesn't have the blue coating on the outside of the seal, nor is it as thick (less surface to seal) and I've had issues when pressure testing drives using Sierra seal kits. So when I do drive work I always go Merc.

Seirra has purchased Mallory, maybe 2 years ago now.