MERCRUISER SEA WATER PUMP 46-807151A9 BILLET ALUMINUM HSG AND SERPENTINE PULLEY | eBay

That style Merc pump? Thinking of driving with 4 rib AC pulley, I can math the pulley sizes and engine rpm to figure out what it would be spinning but dont know what "normal" is

i think they run pretty close to 1 to 1 ratio.

1 to 1

Just saying that's a GLM parts and in the marine world dealing with many parts daily -- many in the industry call GLM = GOOD LUCK MARINE pure CHINA made parts.

Seems that all raw pumps take about the same size pulley, which is smaller than the crank pulley that drives them. Which means they are spun a lil faster than crank rpm. Then there is the direct drive type which, obviously runs at crank rpm. Some alpha vert shafts run a little slower than crankshaft rpm and they are the smallest pumps with least vanes that feed v8 engines. So a pulley the size of the crank pulley would be the upper limit in diameter. I wouldn't go much smaller than what the oem people use. Might spin it too fast.

****. Looked like a simple deal not hard to screw up. Should I take it apart when I get them and use real bearings? I liked the bolt on pulley (I could have another diameter made if I needed to change ratios) and the 5 thru bolts for the housing gave me an easy place to mount the face to a bracket to bolt to engine block. Ordered the two when I was typing the original post :/ Anything else equivalent?

Unable to say anything about the quality but there offering a similar item as Merc (aluminum) or Hardin Marine (stainless). Its not like its hard to make one with a CNC machine. Everything else is simple seals.

Merc has something like that? Have a part number?

Or are you meaning this? MerCruiser Sea Water Pump/Pulley Serpentine Belt, Replaces 46-807151A9 - EMP | eBay

Yes like that
Genuine Mercury & Mercruiser parts. Sea Water Pump

That doesnt have the bolt on pulley