I just had the AC unit serviced and installed a new water pump. My question is this- most regular boats have a "speed scoop" on the thru-hull of the water pickup for the air conditioning water pump to feed water pressure and keep back pressure from pulling the prime out of the pump. I don't really see that design working on a go-fast, plus the factory didn't use a speed scoop and I'm sure there is a reason. But how do you regulate the back pressure to keep the pump from losing prime? I'm worried that every time I use the boat the pump will lose prime and won't pick up water when I want to run the A/C. Would using a water shut-off valve in the water pickup line help? For those of you who have A/C, how are your units configured?

Depending on where thru hull an pump are you should e fine. If pump is low enough it is below waterline and will water there consistently. Just a guess not sure of how it is set up. Has it worked in the past? Might even have a check valve to keep prime.

a flush thru hull on a fast boat will usually loose prime, not much you can do about loosing it, best deal is a T fitting with a bleed valve that you can easily bleed when you get ready to use the A/C mermaid a/c units come with them...but you can build one your self from PVC parts at lowes etc

Mine has a flush through hull fitting. The pump is mounted below the waterline. I have never had to prime the pump. I think the key is mounting the pump BELOW waterline.

Haven't had any issues either. Mine is below water line.

Thru hull, valve, hose, strainer, hose, pump, hose, AC unit......as long as the pump is below water level and those items are mounted with each next item being higher, the system will alway self prime. Avoid having a loop.

Can always tell the boats that have the scoop pickups when going down the lake, looks like their bilge pumps are running.

My pump looks like it's right at about the water level, maybe slightly below, the problem is there isn't much room to mount it any lower or reconfigure. The old A/C pump was bad when I bought the boat so never had a chance to find out if this set up works. Boat is on the trailer now, just spent a lot of money on the A/C and trying to anticipate any problems once it is in the water.

the a/c pump has to be below water line, and some hulls and or thru mounts will air lock almost everytime, worked on many...some will not air lock but many will..

I had the same issue.....but it was due to the fact that I installed the pump in the head behind a panel so I didn't have to listen to it at night. I installed a cheap plastic one inch check valve just after the strainer in the forward bilge and problem solved.

I have a shut off valve and before I put the boat on the trailer I shut it off. Seems to kelp my prime