fresh 350 overheating on the hose

[dude26420]

1985 mercruiser 350 .30 over rebuilt with the good stuff,not in boat,on the garden hose,within minutes of first start up,manifolds and engine so hot you can barly touch it, new manifolds 4" glm center rise with restricted gaskets,new thermostat housing with 140 thermostat.water flow out manifolds is good,but stays the same when running or not? is this a ploblem or do i have issues. any advise or ideas on the heat and flow of would be greatfull,as i dont think this is normall

 

[alldodge]

1985 mercruiser 350 .30 over rebuilt with the good stuff,not in boat,on the garden hose,within minutes of first start up,manifolds and engine so hot you can barly touch it, new manifolds 4" glm center rise with restricted gaskets,new thermostat housing with 140 thermostat.water flow out manifolds is good,but stays the same when running or not? is this a ploblem or do i have issues. any advise or ideas on the heat and flow of would be greatfull,as i dont think this is normall

I think we might need some pics to see what you have. Are you building a closed or open cooled engine?

 

[dude26420]

No Title

open cooling

 

[Bt Doctur]

my guess is the therm is install wrong,upside down.water always has to exit the motor to cool the rubber.the check balls allow water to exit the riser and close when the therm opens and directs the water thru the manifolds and out the riser.

 

[81 Checkmate]

Check what BT said......But i have an 1985 also and i do not have restrictor gaskets. Are the restrictors per your manual?

 

[81 Checkmate]

Check what BT said......But i have an 1986 and i do not have restrictor gaskets. Are the restrictors per your manual?

 

[dude26420]

Small hole in gaskets are front and back lookin at motor, the old manifolds where the same.not sure what you mean by upside down?

 

[NHGuy]

My 88 open cooled Mercruiser has the gaskets set with the openings on the sides like you say yours are.
What he means on the thermostat is to see if the spring is facing down. If it's up the system won't cool right.
When you run town water on the hose will the water pass through when the motor is not running? It should.
Once you have that, you need to see that the thermostat opens with heat, which allows the water though the engine itself. The supplied water bypasses through the exhaust til engine heat opens the thermostat.
If all that is OK start checking your hose routing, and inspecting for obstructions. Maybe your new exhaust parts have some casting flash in them that could obstruct things.

 

[dude26420]

No Title

my manual 1985 ,this is how it was this is how i put it back.i dont have a infired gun. goin to recheck thermostat,maybe try to flush manifolds with power washer. thanks for all the help

 

[500dollar744ti]

Do you have a infrared thermometer so you can see what the actual temps are?

 

[Bt Doctur]

Start at the beginning. who rebuilt it? water will never flow thru the block if the intake manifold gaskets are reversed closing off the water port.the flow is ONLY thru the front of the heads into the intake manifold, out the therm housing.
If you can blow a mouthful of air thru the manifold hose, is not clogged.
The therm goes in the therm housing, NOT in the manifold.again, no water flow.
If you feel its a clog, just stick the hose into the manifolds hose and see what comes out the elbow.
Water exiting the elbows and the block and manifolds getting hot means no water is getting into or out of the block.,

 

[alldodge]

In your cooling design thermostat housing there is a solid sleeve (item 10 in link below) on top the thermostat. The sleeve is used to hold the thermostat down against the housing. When the stat is closed very little water will make it above the stat into the hoses which feed the risers. When water comes in from the hose, it goes through the circulating water pump and into the engine. The stat makes sure the engine is full and only when full will the water pass through the lower stat housing to the manifolds. The manifold gaskets should have slot holes on each side to pass water up through the risers and out the exhaust.
http://www.mercruiserparts.com/Show_...COOLING+SYSTEM

If you do not have the solid sleeve or holes in the manifold gaskets there will be an air pocket in the engine block until the stat opens. Once stat opens water can pass via the top or bottom hoses in the exhaust. There have been many issues with your design of stat housing and some have changed them out for newer style

Your gasket part number should be 27-863724
https://www.google.com/#q=mercruiser+27-863724

 

[dude26420]

I built this contraption, i checked the thermostat and it doesn't.open? Manifolds have the right gaskets in right direction. I used felpro intake gaskets, there open on both ends,thats a good one ,would have never thought of that. Goin to try another thermostat hopefully that works. I should have checked on the newer style thermostat housing a little closer before i bought this one,didn't know of the problems they had with this style. Just hope i didn't wipe the lobes of my new comp cam? Didn't really get to run it for the full 20min! thanks again everyone

 

[Bondo]

I built this contraption, i checked the thermostat and it doesn't.open? Manifolds have the right gaskets in right direction. I used felpro intake gaskets, there open on both ends,thats a good one ,would have never thought of that. Goin to try another thermostat hopefully that works. I should have checked on the newer style thermostat housing a little closer before i bought this one,didn't know of the problems they had with this style. Just hope i didn't wipe the lobes of my new comp cam? Didn't really get to run it for the full 20min! thanks again everyone

Ayuh,... Welcome Aboard,.... The older t-stat housin' ain't so bad, especially in freshwater,.....

A bad t-stat still woulda been bad,....

Good luck with it,....

 

[NHGuy]

If you were breaking in your cam just finish it the next time you start the engine. Go right to your rpm and finish the run in, same break in oil. Don't change it til it's had it's time. The lobes should not wipe if you keep the rpms up which bathes the cam best.
It's the only time I have ever revved a cold engine.

 

[aerobat]

i had something similar on my 5.0 MPI / bravo three - it got very hot on the hose - slowly climbed above 180 deg. i freaked out because the impeller was brand new and the tstat olso.

in my case it turned out to be as simple as the water hose was not able to deliver enough water for a V8 - in water i have no overheating in none conditions.

i would recommend to launch your boat and see if it still overheats before further investigating.

 

[dude26420]

No Title

Ran it for another 10minutes to finish the break in,wasn't as hot,but still seemed to warm.goin to put in the boat and take it to the river and see what happens ,thanks for everyone help