I have never used there seals. but I have used there bellows and had no issue

I use sierra for everything. Never an issue. Much cheaper $$ also.

I have used sierra parts on a lot of boat repairs, the only problem I ever had that comes to mind was a gen 2 impeller that was not glued together properly (between the plastic insert & the rubber impeller blades). I replaced the impeller, showed a factory rep what happened & got a complete refund on both teardowns and a new kit no questions asked. Randy

Impellers are softer and I replaced three circ pumps on a triple with Sierra and all three blew out the gasket on the rear of the pump. They had thick rubber gaskets and would not stay in place. Years ago when I rebuilt Alphas all of the V-8 gear sets failed in the upper, never used their stuff again.

i have a repair shop in texas an sierra all we use,,,,cant beat theyre warranty,lifetime on most parts where merc MIGHT give yu 1 yr, an very very few failures.....i agree with most,they made at same plant an dont buy merc rejects
guees that means they have a little guy on each part assy line that inspects everything an tosses 1 to merc an 1 to sierra...
BS

A couple of years ago I rebuilt a pair of 502 mpi's. As the old long blocks were at such a bad state I sold my customer 2 new GM marine long blocks. When assembling I noticed one of the circulating pumps needed replacement and a Sierra part was the only that could be located within reasonable time.

Everything was well until the customer called me a few weeks later when he was out boating. One of the circulating pumps was leaking and shooting water from the back plate straight at the flame arrestor. 'Damned, is this the one I didn't replace?' I asked.
'No, this is the new circulating pump!'

The dealer that sold me the pump was not that interested in supporting a thorough check-up of that motor (the leak occured at high speed and the driver noticed it by rpm drop).

From that experience and also stern drive seal kits with very poor fitting seals I have stopped using S**a parts

I have used their impellors, no problem. their engine gaskets suck. had issues with exh. gaskets on a pair of 330's looked nlike header gaskets with no compresablity or water resistance. ended up with metal clad Feplro's no issues since

Forgot to mention bellows. I have seen S***a u-joint bellows wear out against the water intake hose in Alpha transoms. Never, never seen that with a Merc bellow.