TomZ's question about water dumps has started me thinking that maybe cooling water pressure could have contributed to my head gasket fail.

Does any one have an idea of what kind of water pressures I can expect with an Alpha 1 Gen II? I have some EMI stainless risers that each have only 2 3/8" holes at their ends for water to escape to the exhaust.
I don't think I need to add more holes since I'd think more exhaust water can contribute to reversion. But maybe I should be looking into water dumps to control pressure.
What's the thinking?

Are you using the water pump that's in the drive? If so I think you're over thinking the issue. My Stainless Marine exhaust risers have basically the same set-up. I don't think there's much pressure at all from the water pump in the drive but I could be wrong. I've never measured it. I would look for other issues if you're having head gasket problems.

not sure NHguy. A bunch of guys that are/where running 60's to 70'smph with reg Alpha's and not a mention of this ever and a few handful of guys 70's thru 80's with SS's having problems either.

Edit in: just noticed where you said EMI's with 2 x 3/8" hoes for watering entering exhaust. Some people ran EMI's on their small block/alpha's, including myself. I did not notice this. Never looked.

Looks like you should take a water psi test to make sure you don't have a water psi issue.

quick math says the area of two 3/8" ID holes = the same area of one .531' ID hole. Hmm.
Again, I would take psi reading 1st. Back off throttle if you reach 30psi or so. Many cloe to 40psi Bravo pump'd engines out there doing fine.

A stock alpha GEN 2 inwhich came out in late 1991 as I have never seen ONE ever produce excessive water flow thru the engine / heads / exhaust and again NEVER seen one. Also 95 percent boats with Alphas are 65 mph and under boats and prob 100 percent OEM totally stock boats with Alphas are 65 mph and under. And 65 mph would be very fast for a stock OEM engine with Alpha..

Anyways -- Alpha GEN 2 floppy vane impellers ( and thats what its really called ) flows less volume of water than a Bravo impeller.

Will say that the floppy vane impeller and SS housing are one tough impeller / housing set up - I seen some pretty tite wad boaters whom never changed them until the temp really started showing hot but had 9 years of use.. I still could not believe those darn impellers lasted that long. And of course NEVER ever let any impeller and gaskets go that long with out changing..

I just realized that I never came back to report.
It turns out that the EMI risers have the holes in their inner tails plus the inner liners have a small gap at the end. So when I ran my engine on a stand I was able to see that there is quite a good flow of water out the ends of the risers. Now that my engine isn't giving me trouble I have stopped looking for reasons to change it.