Freshwater trailered boat. About 600Hrs. Will idle all day at 160* but once on plane were good for about a mile until the temp rises to about 200. Replaced thermostat, which looked good and also the raw water pump with OEM parts, which also looked good and no change. Removed both manifold hoses and stuck a garden hose in them full blast and no water came back up the hose. I was thinking maybe the manifold or riser was bad. I let those run for a minute. Ran a hose from the thermostat back through the coolers to where the hose enters the back of the seawater pump. Full blast on the garden hose and nice clean water came back out the end with no buildup of pressure in the hose. Backflushed the intake hose back out through the outdrive and I was only able to do like half pressure. But then again I assume its a little harder to get water back out through the transom through the hose and down the drive. When we pulled the drive this spring to replace the gimbal and bellows the intake hose looked perfect and was reused. Also the transom plate where the hose goes back through was nice and shiny grey. No signs of corrosion. Once back at idle it cools back off to 160 really quick. Ddidnt check the circulation pump as most people say they never fail. There is ZERO room to look in the back of the motor and remove the transom connector to check for Bravotitis. I have about 6 inches above the intake manifold and 8 inches on the sides to work with. Id have to remove the exhaust manifolds in order to try and get back there. (1998 Maxum 2300) Any other idea or thoughts or ways to narrow anything down? Thanks!
