No surprise to me.------I refuse to use a plastic tank in my boat.-----Give me a steel tank made by OMC in the 1960's / 1970's ----Just good stuff not affected by the sun !!!
Those lower units are easy.----I was repairing them at 18 years old as mechanic at a Johnson dealer !-----Is water 6 or 7" above the impeller in your test bucket ?----Thermostat in place ?
Is the gasket between the carburetor and block the correct one ?----Some have 1 wee hole for the crankcase PRESSURE pulse.----It must line up correctly !