High Sea Water Pressure??

[mike15]

I am stumped! I've tried everything I can think of. I have 2005 300 Sundancer 5 liter MPI Bravo 3s. Both motors have high seawater pressure. 10 PSI at idle. And up to 40 PSI cruising. New Sea Water pumps and new pressure sensors, new exhaust manifolds and risers. Thermostat housings cleaned and new thermostats. Pressure has been confirmed with a pressure gauge on the thermostat housing. The Large diameter hose going to thermostat housing swells enough that serpentine belt touches it. Restriction has to be somewhere after the thermostat housing ? Any thoughts and suggestions would be appreciated. Thanks.

 

[Jeremygavin]

I am not sure how your motors are plumbed but mine are FWC and I had high water pressures such as yours. I cleaned out my heat exchangers and back flushed all the coolers (oil, PS, on my boat) and raw water lines and that was my problem. I got a lot of junk out of them, mainly my engine oil cooler. Pressures down to normal levels now.

 

[mike15]

I should've stated that mine are Raw Water cooled. I'm coming to the same conclusion. I may have to start unhooking hoses and back flushing. Thanks for your reply!!

 

[Bt Doctur]

its water in=water out. the wild card is combustion gas entering the cooling system