I once had a 1989 Mastercraft prostar 190 with a ford 351 with V belts , it had a crank mounted pump , maybe a Jabsco?

F6 Johnson pump

Johnson F6B-9 is the one I’m going to order. It’s supposed to be as good as if not better than the Merc pump. Ordering today and will also look into spacer plates that I can modify for the mounting.

On another forum, a solution was to machine some stand-off bushings to align the pump and also lessen them depth (the serpentine pulley too deep).

I bought these from Full Force this summer for my AT. Just sick of the Merc pumps leaking from the front seal and a pain to change the impeller.
https://cimg8.ibsrv.net/gimg/www.off...1ff5896ca.jpeg
https://cimg9.ibsrv.net/gimg/www.off...13be0f992.jpeg

those are the long impeller ones they pump a lot of water i dont use the metal bracket as thats the part that fails or always rattles the hoses stop the pump from rotating

Specs on the pump state max rpm of 5k. Any concerns running them upwards of 6k?

Another note... be on the lookout for knock-offs. Lots of junk out on Amazon, eBay, etc.

Ordered a pair this morning.

I run those pumps and have run them over 6k without incident. Do pump a bunch of water though! I switched headers that had a small hole to exhaust water and blew the freeze plugs out of one motor! Had to overboard the excess water (and install pressure gauges). Simple, efficient and if you have room, a fairly easy impeller swap. (I use 90* needle nose, but they actually make a little tool to reach in and slide the impeller out)

That's nuts!

I'd imagine this is especially important on a Gen VI block where the water jacket to side of the block surface is thin. My 502s seeped at the head/block joint due to high water pressure. It'll no longer be an issue with closed cooling but it was a big problem when raw water cooled and at speed.

Found this on the Formula Boats forum... good list of parts.

How-to: convert your Merc raw water pump to crank-driven Johnson (take 3))