I haven't yet identified where the water pressure reading is being obtained from. But I've only got 5-7psi at speed.

Have you tried a temp temp gauge to verify?

I have not, yet.

Update:
water pressure gauges are reading from the block drain(s).
Still only seeing 5-6 psi max at speed.

Ran it today, brought my IR temp gun with me. On both motors, the starboard cylinder head reads 40-50 degrees warmer than the port cylinder head.

Water temp gauges appear to be accurate, based on taking IR readings at the sender on both motors.

Starboard motor runs about 20 degrees warmer than port motor overall - the water coming out of the oil cooler on the starboard motor is 20 degrees warmer than the water coming out of the oil cooler for the port motor. This is the water that's being fed into the crossover on the front of the block.

I am not sure where to go at this point - but something's got to be wrong here. I was seeing 200 degrees on the starboard water temp gauge for a while, and that's way too high. And, this was also at speed, not just at idle. Of course, I backed off the throttles when I saw the temps climbing.

I am close to installing circulating pumps on the motors - at least that would help equalize temps across the cylinder heads - but is this likely to be the solution to the whole problem?

Thanks!

My block drains are clogged within a month after I clean them out. A lot of coolers have a port for the gauge.I have also drilled a port in the front of my manifold under the thermostat.

Block drains one of the worst places for permanent water pressure readings. the deposits that form and collect there never ends with raw water cooling. Even worst if one does not have a really good sea strainer.

Also they are one of the lowest points for water drains - another reason why crap collects in the area

Well, I discovered a badly cracked gimbal ring on the starboard side yesterday - so that motor is coming out. That will give me an opportunity to verify all the rigging and to relocate the water pressure location.

Is the port in the oil cooler really the best place for measuring water pressure? Is it really representative of the pressure in the block? Or does that not matter since it's after the sea pump? I have 2 new oil coolers on order from Hardin.