Going to the thru transom mounted pick up is likely to further raise your water pressure. On my drive the water enters into a 5/8" hole, which really creates a lot of ram. I am a thermostat fan rather than the flow restrictors. That could very well be where part of your problem lies along with the McMaster Carr valve. The valve and tee I use likely has more flow capacity than the McMaster valve. Does your crossover have a bypass? If it does then my tee and valve system will fix your pressure problem as well as allow you to run a thermostat to maintain consistent temps whether idleing or running WOT. I have a couple of valves and tees left and if you are still having problems after your new pick up I will ship a set for you to try and if it works you can pay me, if not send it back. The check valves I have are preset at 5 PSI cracking pressures and tee into the inlet line before your strainer or sea water pump and dump water once inlet ram hits 5 PSi. The check limits the inlet pressure and stops spikes before they even get to youe sea water pump. Stainless Marine has a similar setup on their sea strainers. Good luck and PM me if you want to take me up on my offer.
Craig

I'll be in touch. The first thing is to get this back up and running. The transom pickup is being added because, even the low water pickup isn't low enough. I'm sucking air, buring up the pump and thus cooking the motor. Hopefully, the new pickup will induce some reliability.

Re: Is 33 at wot too much?
 

The 496 has a closed cooling system. I would guess your pressure is tapped off of a water line after the sea water pump. Since the engine cooling system is isolated from the Sea Water side the engine doesn’t see the high pressure. The coolers can take more pressure than the engine. If this is the case you will be fine. Let us know where Fountain is taking the pressure reading.
Dan

Duh, I should have known that
 

Thanks candyman, I'm concerned about nothing.
I'll check anyway to see where they tapped it. JC

The 496's are tapped @ the pump. Merc. has a low press. alarm, part of its guardian package if your's is connected. It includes drive oil resevoir, start-up squeal, etc. (mine stuff is in a bag where it belongs).

Wette;
How do I get information on your bleed off system?

Tantrum or anyone else interested just send me a PM with your phone number and I will call you to discuss your application.
Craig

Hooked garden hose up to headers and they flowed great (took sparkplugs out to be safe), will try "t" and valve tomorrow as its fathers day and wife can't say no to helping me.

HIGH PSI
 

Fresh water cooled, normal water pressures before rebuilds, did the "T" s with valves before headers, opened full and pressure dosen't drop, 2500 rpm 35 psi, 3000 rpm 45 psi approx, did this test with boat on plane and with boat in neutral to eliminate ram effect, any suggestions?

jeffg,
That eliminates the headers as the problem. What changed? Did you install a cross over to replace the circulating pump? Could there be a wrong gasket being used? Maybe some water passage is blocked. Are you reading the pressure at the same point you used to? Where are you tapping off for the pressure gauge? If it's not the headers then something had to change. It would be better to fix the problem than just install a dump like I did. My problem came from the factory. I still have no idea why my stock 454 mags had high pressure. I think that's one of the reasons Merc is going to closed cooling systems. Let us know.
Hope it can get figured out soon.
Dan