Out of water, it will idle/run fine. Once the pump is submerged and water goes through the engine, it starts to stumble and then finally will shut off. If I feather it, it'll stay running and once I get going(passed no wake zone buoys) it runs excellent.

I've tried upping my pop off(had 10psi at first), messing with low screw, can't seem to fix it.

It was a project ski when I got it, I resealed the motor(and carb) and leak down test passed. Tested both internal and cooling, both good. I've checked my head orings tons of time and they are always seated correctly. I had the exhaust manifold and exhaust surface on the jugs decked flat. Had a small water leak from a warped manifold.

I've realigned the engine/drive line/pump and its lined up excellent.

The only way I've been able to temporarily fix the idle in the water is turning up the idles which then makes out of water idle way too high.

Specs of the motor if it helps:
165 even compression
Ada girdled head
61x engine, jugs bored to 84mm
B pipe
Sbn44

Any help would be appreciated, thanks