Its the same kit the Sierra brand even has the same part # on it as the Merc brand plastic housing - just different box thats its. You can see the same problems with both kits nowadays.

Both kits can have flash inside the black plastic housing where the water ports are so watch out for that plus the edges can be very sharp.

IMO the clean up in the water ports of the housing is very poor. I sell Mallory Marine parts also on top of the other brands. The Mallory kits are alot better plus beefier - the housing weighs more and is finish off alot better than either kit from Merc or Sierra.

You would be surprise how many parts that are the same from Sierra and Merc and even Mallory. Oils are not the same from these. FYI.

Good point, I always clean/deburr the plastic casting flash/parting lines in the plastic Merc. Impeller housings.

Alot of the Merc parts are the exact same as the Sierra. Just in a different box.

I have had exactly the same experience, NEVER happened with Merc parts.

I have also been asked by customers to use Sierra seal kits for stern drives but feel they are questionable since the seals does not have the same fitting tolerances as Merc parts. Some have loose fits, some almost can not be pressed in place due to tight fitting.

Some parts however seem to originate from the same manufacturer but it takes a trained eye.

That's the same explanation I've heard about Serria vs Merc parts. Many are made by same company, but to different tolerances.

As a toolmaker that had worked in the manufacturing business, that does not make sense. I can not see a company having 2 sets of mold dies made to different tolerances, to make the same part. The only plausible explanation is that the parts do intact come from the same mold, using the same raw material, but some parts may fall out of the tighter tolerance range (die wear?), thus branded Serria. Seems like a stretch though
Not sure I'd buy a different raw material theory if stated either.
Mold dies are made for specific raw materials for a controlled shrinkage factor. Different material=different die clearances=another die set=$$$$

It's all the same stuff. I think people just want to spend more money and will always come up with a reason to do it.
Could you imagine if it was crazy busy production that pushed them jar at the factory. Would they purposely start making bad ones to keep up orders ? Would they start screwing merc with 2nds to keep up. You get my point. They are all built the same. It all built to an economy of scale. Them the marketing makes up the difference.

That's what I was saying, it didn't make sense to make the same parts differently. Same as Mercury vs QS. I just don't see that huge of a demand for all the tooling required to make all the parts offered for sell in competition to Merc.
A marketing tool. I've purchased the Seirra water exhaust drains and blue drain screws. Same markings down to the parting lines.

Sometimes a tier 1 or tier 2 / 3 supplier to an OEM will also be able to sell the same components as supplied to the OEM under their own brand name (or brand of another).

Example: Ford and GM don't build everything in house. They have contracts with outside suppliers for just in time manufacturing. Sometimes those contracts are not exclusive, for a variety of reasons - usually cost.

Porsche is another example. They use Mahle pistons and cylinders, not manufactured by Porsche. Buy from the Porsche dealership and sometimes they say Porsche on the box. Sometimes they say Mahle. But you can also buy (if you are in the industry) the exact same Mahle pistons and cylinders without buying direct from Porsche.

I don't know about Mercruiser, but I expect the same thing happens as it does with almost every OEM.
Also agree with US1 Fountain, differing tolerances or manufacturing from the same plant makes no financial sense. The whole reason it happens is to save money at the manufacturing level, not spend it.

The real question is, are the parts made in the same plant? That should answer your QA question.

after inspection,the merc rejects are put in a sierra box...
:lolhit:

Should I stop by and ask for a tour to settle this? Lol