boat overheats on muffs running at high RPM's

[QC]

Re: boat overheats on muffs running at high RPM's

OK Murk's Bro, just trying to point out that without load there is no way to confirm it will not overheat on the "big water".

 

[Haut Medoc]

Re: boat overheats on muffs running at high RPM's

OK Murk's Bro, just trying to point out that without load there is no way to confirm it will not overheat on the "big water".

I agree....
I'm sayin' it should never overheat in the tub or on muffs....Period....

 

[QC]

Re: boat overheats on muffs running at high RPM's

Kewl.

One scenario for clearing my murky, one cell, brain though . . . high RPM causes hose to collapse, pump cavitates causing impeller damage, impeller damage causes low flow, causing overheat. That doesn't happen? If not, why do we ever recommend against running high RPM on muffs?

I learned that here, although I never let my engine run high RPM with no load anyway . . . Not sure what it accomplishes except maybe checking timing advance

 

[Haut Medoc]

Re: boat overheats on muffs running at high RPM's

Sorry to interrupt all the quibblin', but it should not overheat either way- hose or tub at any rpm with no load, the exception being the hose collapses from vacuum......​

Me neither, other than checking advance, like you said....

 

[Maclin]

Re: boat overheats on muffs running at high RPM's

HM and QC.....True that, I should have made it clear that in my response I was focusing on the behavior of the raw water circuit in regards only to volume of water in and out. That was one of the parts of the answer to the original poster's question(s).... I felt like he was outrunning the muff adapter, so if he really needed to run it longer and at higher rpm the tub method was one way to eliminate any muffs feed problem as an issue so he could focus on the impeller or whatever if raw water flow was still not good.

I feel very confident that my cooling system will perform as designed in the big water once I have observed how it behaves in the tub. But again, my system does not work well at all on the hose adapter.

And to 302Mustang: I do feel you could have damaged your impeller during the time you were running on the hose adapter. And maybe head gasket or other problems could crop up too, as in my opinion 250 degrees is really high...I am assuming you do not run a closed cooling system here. Remember the water reaching the engine is not pressurized and will boil at 212....radiator systems in cars are pressurized and for each psi of pressure the boiling point of water raises a few degrees. Since the water coming into the boat engine is not pressurized then it can vaporize at 212.

 

[Bondo]

Re: boat overheats on muffs running at high RPM's

Re: boat overheats on muffs running at high RPM's

--------------------------------------------------------------------------------

Quote:
but just what type of rebuild did you complete that did not include an evaluation or replacement of the thermostat??

Ayuh,.......... Define Rebuild.....................

And,...........

Quote:
but if I spin it up to high RPM's for a period of time the motor overheats. I have it on muffs

Define High RPMs,............
__________________
Any Grease is Better,..... Than No Grease at All.......

Ayuh,..........

I just wanta know these answers..........What happened to Mustang,..??....


Btw,..........

Since the water coming into the boat engine is not pressurized then it can vaporize at 212.

That's Not quite True...................

With the restriction in the block,+ the rest of the cooling system, Then the small water outlets in the risers,.....
The typical marine Impeller Pump will develop 7 to 15psi,+ Up,......

My garden hose,+ muff connection bleeds Water profusely whether at Idle or up to 1500/1800rpms,............
No Problem....... Plenty of Volume.......

 

[Maclin]

Re: boat overheats on muffs running at high RPM's

Hey Bondo,

Good stuff to know about the cooling system, I had no idea the block could see that much pressure with the typical open cooling system, thanks.....