Merc 115 OB loosing water pressure at high RPM

[WWBrown]

I have a 2019 Merc 115HP outboard SN 2B669032 with 120 hours on it that is loosing water pressure after a couple of minutes at high RPM. I am fine at idle, 5 psi or so and about 130 deg temp (VesselView). I increase throttle to to cruise range, 4 to 4K or so and the water pressure increases to 20 PSI (boat gauge) and the engine stays about 30 deg temp. After a couple of minutes, the water pressure gradually drops to as little as 3psi and the engine temp increases to about 150 deg and stays there.

I call Mercury and they say the PSI should be at least 10 psi and the dealer has already changed the pump and thermostat; no effect. The engine is still under warranty but the dealer say neither are covered. So, I am out $500 to date with no change.

Note I did not get VesselView till recently so originally I did not know what temp the boat was running at. Also, RPM between 3500 (plane rpm) and 5000 have no effect neither does trim.

I could use some help understanding if this is normal and if not, suggestions as my dealer does no know.

 

[racerone]

How high is the transom ?-----It could be that motor and transom height are not matched properly.-----I say motor may be mounted 1" tooo high.

 

[WWBrown]

How high is the transom ?-----It could be that motor and transom height are not matched properly.-----I say motor may be mounted 1" tooo high.

I am not sure how to measure, its a Tracker pro V 17 so came out of the factory this way in 2019. the thing is, the pressure does go to 20 at high RPM and stays there for a couple of minutes before dropping off. there is still water coming out of the tube but not a strong stream