455 Oldsmobile Jet Boat Overheating

[brando]

I Just Purchased A 1974 Sleek Craft Jet Boat And Over Hauled The Motor
New Head Gaskets ,intake Manifold And Gaskets, Exhaust Gaskets
Pan Gasket Etc. When I Run The Boat Throught The Hose Outside The House The Temp Will Increase From 120 To 220 In About 2 Min
Changed Thermostat 160 Mabye Ill Try Lake Test Still Same Thing
I Have Hardin Marin Exhaust My Question Is Can Those Exhaust
Be Pluged Up From Sitting And Possible Restricting Water Flow
I Even Pulled The Thermostat Out And Ran It And It Still Got Hot
Any Answers Would Be Of Help
Thanks Brando

[seeds]

is is definitly a water restriction. check your water pump, or the lines. occasionally they get clogged. it may be hard to find, but it'll happen. good luck.