Sea strainers and blockage ?
 

I've got a transom mounted water pickup that doesn't have any type of screen on it and then I have strainers. Recently the strainers and pickup got blocked with seaweed. The water pressure and water temp gauges never moved, the first indication of a problem was a rise in oil temp of one engine. The engine got hot enough to discolor the headers. Questions- why wasn't there a noticeable drop in water pressure ? Is there something that can be changed gauge wise to show a water restriction quicker? Also once the strainers were cleaned, the through hull intake was clogged as well which would mean jumping in and going under the boat to clean or jumping in just to check it. Would it work to weld some sort of stainless screen onto the pick-up to prevent it from getting clogged?

Livorsi Raw Water Flow System http://www.livorsi.com/catalog/water_flow.html

That would probably do the trick. Any experience using it?

I saw it on a few boats at Buffalo Poker Run this year and I looked it up to get educated. It sure has a lot of positives to it, my next boat will have it.

My transom pickups have a screen, or should i say welded plate with many small holes drilled in it.

Great example of how they work. Was idling thru a harbor that had a bunch of seaweed floating around. Noticed one engine temp getting warm. Simply shut that engine off, waited 30 seconds, started it back up, cooled right back down. By shutting the engine off, the seaweed that was stuck to the grate, simply floated away.

With these pickups, i have 25psi of water psi at 5500rpm.

I think I'll be doing the screen/plate and the gauge unless someone has some bad experiences with them. Just need to find more room on the dash

Are you using an electric water pressure gauge or mechanical gauge with a small hose from somewhere like the intake manifold to the gauge? IMO, a mechanical gauge with a small hose from the intake manifold is easy way to rig for WP and it is very consistent. With all the weed in Lake Erie the last few years, we allow our water pressure to run down to about 5 PSI and then stop and clean out the strainers.

I have mechanical and idiot light sender and temp sender all coming off front of intake. Nothing budged other than the oil temp rising

It seems to me that if your sea strainers were clogged, you will lose water flow and pressure. Your headers confirm there is a flow issue. Something isn't right with your WP measurement system.

Water pressure remained constant at about 20 psi or thereabouts. Mechanical reading off manifold directly below the thermostat housing.