I know in my case (a Formula 272 with big blocks) replacing the Merc impeller was a REAL MOFO if you get my drift:rolleyes:
After a lot of question asking and research I went with this set up and it works. Best part I can kneel on the back seat , lean over the backrest and change the impeller in 15 minutes. It's almost the same a BB Volvo and theirs works;)

Looks alot like my Volvo Set-Up...

Duh, Well....I'm back in work again. Have to wait till morning again for pix:( . In a nut shell , it's the same place Merc put it. Right above the alternator on the right side by #1 cylinder. Film at 11:D :D :D

Pat,
That's why I finally went with this setup. I had talked to C Spray who has twin Volvos in his Formula. I had my doubts since the flow rating is just over 1/2 of the Merc belt driven pump. With a circulating pump I have around 9 lbs water pressure at anything over an idle. I've also heard anything past 2000 rpms the blades on the impeller just lay back , acting more like a blender and don't do much because the water is being forced in by your forward motion.

I like it!!! the old Merc set up sucks!!!now if you can figure out how to mount the starter in the front !!!

AND HOW!!!!!
Dyno , the other pix

Here's a shot of the oil cooler and plumbing. I figured you'd get to that sooner or later:D :D :D
Hope this has all been a help;)

Sure has!!thats a big a$$ cooler.....If I have a couple extra $100 when I build my 496's there on!!what impeller do they use?

My coolers are for a Merc HP500 and when you get your pump or pumps , why not get a spare or two.
I didn't and was able to match something up at Boat US. After that I ordered a few just to have them;)

Sut,
Yeah, I did pick it myself.
The magenta color on the intakes and t-stat housing is powdercoat that matches some of my upholstery and graphics. Also had the aluminum valve covers clear powdercoated so I'm not polishing all the time:cool: . The rest is just Merc Phantom Black.