200 mercury xri overheat and high water pressure

[Smittys1]

I have a 94 200 horse black max xri. serial #OD271549 a couple year ago I broke a piston and a sleeve. after repair I can put boat in water and drive sometimes 10 miles at full speed. after fishing awhile and I start engine and start to accelerate the temperature alarm sounds and my water pressure is pegged past 30 and around to the peg at 0. slowing down to apx 1500 to 2000 rpm the temp alarm goes off and the pressure is lower but still high, I have taken the poppet valve apart 2-3 times and see no problems. put boat on trailer and next time I go out the pressure is fine and no problems until after a long run. if I remember right once it happened right off the trailer as soon as I started to accelerate. I would like to purchase a poppet valve kit but am having problems locating it or instructions on proper installation. Im thinking the high water pressure is holding the thermostats closed? but not sure why pressure is high. read something about a Simon poppet kit also? thanks for any info and help. Smitty

[JOE54]

do a leak down or compression test , possible compression in cooling system

[lpugh]

do a leak down or compression test , possible compression in cooling system

I have seen this twice on a 200 efi and a couple of times on Autos. The symptom fits a combustion leak perfectly. They do not always force water into the combustion chambers. and the problem can be intermittent. I am sure Joe has seen this more times than I have since I am a automotive guy mostly
I think that motor is very easy to pull the heads on for inspection.
Might show up on the muffs with plugs out and warmed up first, if you can get enough water pressure. at least it would not have to overcome combustion pressure to get into the cylinders

[JOE54]

very easy to pull and replace gaskets