1987 Looper v4 140 RPM only 4000

[nymack66]

I swap my prop at Boaters World for a 13 x 15; I will post the results when I test it in regards to speed and RPM at WOT.
I check the diverter valve it was installed correctly.
I think I found the high temp issue both Diaphragms on the thermostat installed backwards! And the little hole on it plugged with gasket sealer!! This installation will prevent water from flowing thru the heads!
I followed the diagrams from the OMC manual when I install this some months ago, it wrongfully shows the diaphragms backwards so I install it that way, despite my reservations at the time since the engine had none installed.
Today I check the OMC Service manual low and behold it clearly shows the correct orientation for the darn thing.
This is clearly why Jessie Ventura says you can’t write legislation for ignorance, I clearly could have been arrested and charged :) I blame the parts manual.
I also installed the second Temp gauge toady and connect up. No time for testing on the lake. Did a dry run on the muffs checking for leaks, looks good.
Thanks for all your help and attention.