Makes sense to me.  You're keeping the water flowing in one direction, through both sides of the engine (front to rear).  It's actually a mystery to me why we don't have cooling issues on these engines with the "normal" cooling set-up, since you're supplying and removing water from basically the same end of the engine.

On my Olds I've been running a "center feed" cooling set-up for several years: I removed the center freeze plugs on each side of the block, and made some inserts that allow me to feed water into the center freeze plug location on each side of the block.  I tapped all four corners of the intake manifold for water outlet fittings, and tee'd the pairs together on each side (left, right), feeding two thru-transoms out the back, above the water line.

Your idea actually makes more sense, since flow through each side of the engine can be easily/regularly verified from the driver's seat.  Carry on.....

Matt

HomeBlown and I did this set up on my boat (yet to be ran) but I can send pics if anyone needs.

Solid basic setup!   

Personally, I've had problems with the std spring loaded T valves, hence the driver mounted micro valve for the headers. Never a problem with the other boat with std logs, OT pipes and no OB dumps, though.

I've been toying with the idea of tapping exit water from the rear of an engine for awhile now, but one thought has stopped me from trying to destroy thousands of dollars worth of engine. Trapping the (well, lets face it, not pre-heated on a header equipped engine) water and forcing it to stay in the engine a bit longer would tend to increase operating temp. A good thing, since these boats end to run from 100 to 160 degrees depending on the boat and who you talk to. 180 or a tad higher would be great if we could acheive it, but only running a thermostat would that be possible I think. Then the pressure valve would come into play. Or pressure regulator, to be exact.

I've been giving more and more thought to a few boats on here that are running water pumps. GT I think put it best that it's pretty common to do so in the PAC NW on River boats where the water is much cooler, and honestly, the water pump would likely act as it's own pressure regulator. Coupled with a normal thermostat, makes almost complete sense to have an open cooling system that held a pretty consistent water temp with that hardware. Unfortunately, my crap is all so weird that theres just not an easy way to test this theory on the local Socal or AZ lakes or the lower River.

Ray

I have had few jet boats and always ran the cooling the same way ( in the water pump fittings and out the thermostat out let). I am considering running into a stainless crossover and out the rear of the intake on either side of the dist. into two dumps at the rear of the port side of the boat so I can keep a eye on it also I will be useing a preset pressure relief valve dumping in the same location, the headers are dry with a manual valve to add water if I need. ANY opinions on this?

 I have thought about running dump lines from the back of the intake like that just to clean up the look of the motor, but changed my mind about it.  I might be wrong about this (wouldnt be the first time), but with the angle these boats sit in the water + the angle of the motor in the hull.  Your going to create a huge air pocket in the front of the heads without some way to let it escape.  I would still run a small dump line from the thermostat area (highest point of the cooling system) just to sure there was no trapped air in there.