Originally Posted by Dobieman
I was told that the water pump is 'low velocity' or something like that,
I believe that the older (like pre 1908s) Merc/ Mariners had two "flavours" of pump - one was high flow low pressure, the other was (relatively) low flow, high pressure. I don't believe they were cross - compatible (i.e certain HPs had the flow pump, others had the pressure type).
I sussed this out by accident whilst piecing a few pages of Clymer together, so don't read it as gospel! (Outboardtech might be able to confirm?)