new long 454 bravo one overheating

[jeffssgtusmc]

I bought a new long block with domed pistons (415hp instead of 330). I bought a new raw water pump and a new circulating pump 140 degree thermo. Within 5 to 10 min of running motor gets super hot it has steamed out exhaust. The last time I tried restarting and starter wouldn't turn it over. Took out all plugs and they were a little black but no water in cylinders. I have the thermo in the top of houseing not right on Intake. Is this wrong. Im wondering if since motor is new is there that much friction that it gets so hot. Thinking I may replace hoses next. Im not sure what to do. I am running with muffs. Fuel is a couple years old also. Any help is appreciated

 

[Don S]

Re: new long 454 bravo one overheating

I have the thermo in the top of houseing not right on Intake. Is this wrong.

It depends on the type of thermostat housing used, there have been many styles over the years. Do you have the Merc serial number for the old engine?

 

[dubs283]

Re: new long 454 bravo one overheating

so you know the t-stat was installed wrong?? (hard to follow your wording)

5-10 minutes of running with little to no water?? was it five, ten, seven?? in any case i think you definitely have some cylinder wall scuffing at the very least, not to mention possible melted pistons

you had it running on the muffs and didn't notice water flow/check temp guage/feel around the motor for extreme heat??

 

[jeffssgtusmc]

Re: new long 454 bravo one overheating

The serial number of old motor is b849705

 

[jeffssgtusmc]

Re: new long 454 bravo one overheating

Temp gauge didn't go over 170. I shut it down when it seemed to hot. I did check for flow out exhaust and there was flow. When I took thermo houseing off the block was full of water.