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1986 454 BBC intake gasket and oil question

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powerplay38

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I noticed that a corner on my intake gasket was popping out so I bought a new gasket kit from my local mercury dealer and changed the gasket. I didn't use the rubber gaskets on the front and back of the engine. I used the recommended gasket silicone that the mechanic told me about. I replaced the gasket set and let the engine sit over night before I started it up so the silicone had time to set up. the next morning I hooked it up to the ear mind muffs and it started right up, I timed it back to 8°. idled it back down to 650 rpm. temperature at about 160 or so. after it ran for about half an hour I shut her down so I could change the oil. I drained the oil and replaced filter and new sae40 oil. when I started it back up, the temperature was running hot quick. 200-220. I shut it down immediately. I had recently replaced the impeller and housing in the outdrive too because I was sitting in mud for a while at the marina last year. had a bunch of zebra mussels on the bottom of the boat and outdrive. I'm shooting a good spray of water out of my exhaust when it's running also. I think I gave you guys as much information as I know of. now with all that info can anyone give me any ideas about what the hell is going on here with this engine?
 
when I started it back up, the temperature was running hot quick. 200-220. I shut it down immediately... had a bunch of zebra mussels on the bottom of the boat and outdrive.
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The temp will spike when you restart a hot engine but should have started coming back down as the cool water entered the block w/in 30 seconds...did you wait? Open the T'stat hsg and inspect for debris in the T'stat...change it if it looks full of crud.
 
Yeah I know the temp will spike in a hot engine right away but it never came back down. I let it run as long as I felt safe , probably a few. it was late afternoon yesterday and it was sunny and hot so I called it quits for the day and never opened the thermostat housing. I'm heading out right now to crack it open to see what's in there. could I buy a thermostat at auto zone or any place like that?
 
just pulled the thermostat out and there was no crap in there. I also put the thermostat in 160° water and the tstat opened properly. Now I'm confused. could I have messed up when I put the intake gaskets in? I'm a millwright and a mechanic. I've done hundreds of intakes and head gasket jobs on cars in the past. not a single one came back bad. I'm at a loss for answers on this dilemma.
 
a 160 deg stat in an '86 sounds like it is fresh water cooled...did you purge the closed side of the cooling system?

if it is a raw water cooling system, you'd be better off with a 143 deg stat unless the boat only sees clean fresh water.
 
It was running at 160 F. for 30 mins. and all you did was change the oil and then it overheats? Air in the system will make it overheat. Maybe it wasn't getting enough water to the muffs?
 
I live in Illinois right on the Mississippi river near lock and dam 13. and all I did was change the oil. I pulled off the hose coming in the boat from the outdrive and checked for water flow and there was nothing coming in so I took the garden off the outdrive and flushed water backwards thru the outdrive. after that I got good water flow thru the exhaust. I decided I would put it in the water just to see if it was just starving for water because the garden hose wasnt pumping enough water into it to keep it cool. I ran it for three hours and it was running cool. I guess it's fixed but I have no idea what the heck happened still and it still bothers me not knowing what caused all that ruckus.
 
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