Ok guys, yesterday afternoon my water pressure in my right motor doubled. It was fine one minute and then doubled the next. Stayed this way the rest of the day. Normal pressure was about 18 psi while running, now I am pegging a 30 psi gauge. Water temp is the same. I would assume I have picked up a stick of something, where should I start? Where is the sender on a stock 350 mag mpi motor? I do not have sea strainers, I do have sea pumps and stock circulating pumps. The pressure gauges were installed from the factory on this boat.
I need to get this fixed in the next two night, heading to cumberland on thursday morning...
Thanks

You may either have a bad gauge or thermostat, picked up something or have another type of restriction causing back pressure. If you have tubular headers, they may have become partially blocked and in this situation water turns into steam.

If you have a thermostat try changing that and then the gauge.

Based on some other threads it appears that the sending unit should be in the block or intake, it is not on the intake. Pressure is read from block and the only place downstream of the block is the exhaust, so I would assume the that any blockage would have be in the exhaust. If I had a thermostat problem I would think I would have less pressure not more. This could be a gauge or sending unit problem I guess.

If I run at a steady rpm the pressure will slowly drop to normal, as soon as I increase rpm then the pressure goes back up again.

Ohh yea, thru hull exhaust, no silent choice or quick and quiet. does not use the Y pipes at all.

If you're getting plenty out the exhaust I wouldn't beconcerned since your temps are the same. Mine runs 30-35 psi.

I think I figured it out. There was a piece of an impeller blade wedged in the inlet bypass side of the thermostat housing. Only two blades were broke, I just wonder where the other piece is stuck...

Back flush from the circ pump thru your cooler after you take the "out" hose off your seawater pump.