Angry merc 9.8 owner refuses to lose overheat problem

[jbjennings]

Cursed mercury 9.8 is possessed by the devil. i have checked everything from water jacket, water tube, water tube seals, pump, and changed impeller. the impeller dish does seem to have a Very slight dimple near the shaft where it appears someone tapped on the shaft impeller key and dinged the aluminum. could this be the problem? this darned mercury is so strange! when at very low idle, its telltale stream is good and feels cool. anything above that and it begins to pressure up some but become intermittent, appears like somebody put their finger over the telltale hole like putting thumb over end of water hose, but there is no restriction! it will never begin to put out steam at wide open after even 7 or 8 minutes of wide open throttle but i can tell it's a weak water stream-no volume and it gets hotter and hotter when i touch the block. Any help?
jb

 

[Bob_VT]

Re: Angry merc 9.8 owner refuses to lose overheat problem

Your engine sounds like it needs all new gaskets. I have seen similar things happen on lager engines where an internal water jacket gasket is leaking.... the hotter it gets the more it expands and leaks. W/O knowing the exact engine.... look up a manual and read about the gaskets. My inline 6 cylinder has "internal" exhaust plates that are notorious for leaking and causing failures.

Does it have a thermostat? If the t-stat is not opening the small bypass will not allow for sufficient cooling either.

That's my guess.