Can a stock type mercurser sea water pump handle the rigors of cooling a 800hp intercooled engine with transmission ,power steering , and oil coolers

I would use the older style what is called the Gen IV and or race pump - they are OEM Mercruiser. I have them in stock and use them as well. Retail is 600 bucks - I strongly recommend changing the water input and water output fittings of the impeller housing out to the bigger ID. I have them as well and is an extra cost. My feelings are --- a cork in the cooling set up is a much bigger cost. ( meaning engine damage).

If I recall correctly they say rated up to 1000 hp.

My thought is it depends on the load and what you had in the beginning and what was changed.

If your boat was setup with lets say 400 HP and it performed fine and without issue then the standard should be ok, but may need dual pick up or thru hull for supply. If the boat labors and is under heavy load at cruise and above speed then it may need more

Merc 900's came with the standard 2 piece housing and impeller.

Thats correct and thats the exact pump I am talking about in my post above. Alot call it the race pump and or Mark IV pump. The thick brass fittings that the housing comes with are IMO too small diameter. I change them out to alot bigger ID. the OD stays the same for 1 1/4 water hose

Like I said If I recall its rated up to 1000 hp.

here is it exactly. and yep like I said good up to 1000 hp. I have about 10 of these all brand new. Pretty common seller for me.

Shipped $ 550 for anyone as seen in the link below.

$ 600 shipped with the bigger ID fittings to your door

https://teaguecustommarine.com/em001...-sea-pump.html

Teague is a bit high, I'm finding the pump around 375 just searching on 46-72774A32

I have the IV race pumps and I am adding intercoolers to my vortech super chargers and i wanted to make sure there was enough water to keep everything happy

IMO the 2 best things to add to a motor is water pressure gauge (on the block) and oil temp gauge. If water pressure and oil temps are within norms, your good (already know water temps)

I already have them , I would just like to know if there was anybody with a similar setup that ran it with out any problems so if there was i could take care of them and not be chasing issues during our short boating season