over heat / head gasket issue

[Thumpbass]

i was running my '78 85hp johnson on muffs in the driveway a couple weeks ago (getting ready to take her out). the over heat horn sounded and i immediately shut the engine off.
water pump indicator was running strong so i installed a new thermostat kit and the motor ran fine on the muffs w no over heat...but i did notice water weeping from a few screws on the flat back exhaust plate...before pulling the plate and replacing the gasket, i checked the tension of the weeping bolts and sure enough they were a little loose compared to the rest of the bolts...so i simply torqued them down closer to spec and fired the motor back up.
the weep/leak on the exhaust plate is gone so tightening seemingly fixed that but now there is a small constant stream of water shooting from between the bottom of the portside head and block..
I assume the head gasket has failed and probably because of the over heat so what Im tryin to figure out is i this is normal or to be expected even if the warning horn buzzed for a matter of seconds (did shut off immediately) and its just as simple as replacing the head gasket and should be fine or if this means more than likely that the head is warped and there is much to be done to get things back to being right...any help/info would be appreciated...thanks

 

[Thumpbass]

Re: over heat / head gasket issue

just to clarify...the stream looks to be between the head and block not the head cover and head

 

[HybridMX6]

Re: over heat / head gasket issue

Probably won't know until you pull the head off, which you have to do anyways if it's just the head gasket. I'd say order a new head gasket, pull the head, and check it out. You can check the head for levelness by laying it on a piece of glass, and looking at it from underneath to make sure it is touching all the way around. The overheat may have gotten worse once it was shut down since it was already overheating and then the cooling was also removed, and the heat built up. Not much you can do about that, it's shut it off and hopefully avoid any further damage or let her run in idle and see if she cools off. I'd probably shut it off too instead of risking a much worse problem, i.e. blown motor.

 

[Thumpbass]

Re: over heat / head gasket issue

In the event that the head is warped, I have a '79 100 powerhead I use for parts (busted rings on starboard side)...assuming the port side head on it is good, would it replace or be compatible with the '78 85hp block? I know that the '78 85hp block is the odd ball of the "cross flow family" the piston displacement is 92.6 cubic inches where as the '78 115-140 and '79 and up cross flow v4's are 99.6 cubic inches (or something like that).
would the fact that the '78 85hp being 92.6 and the '79 100 being 99.6 make them incompatible even though they're both v4 cross flows?