Onan MCCK 6.5 losing prime

[tditterline]

Hi Folks,

Have a 79 F-36 with the original Onan 6.5 MCCK on board. runs perfect, but all of a sudden last year it would lose prime- no cooling water coming out of the exhaust. I've replace the impeller but trouble remains. If I manually prime it, it'll pump water like crazy, but after you shut it off for even an hour, it'll lose prime.

I'll replace the main hose from the seacock in the spring- perhaps that is leaking air, but does anyone know if there's any other parts I should be looking at regarding cooling water?

Thanks in advance from Snowy Central NY.

[prowlersfish]

Several things can cause this , porous hose(s) on the intake side of the pump . A bad seal in the raw water pump can suck air , you may see a water leak there after shut down . And a issue with the vented loop .

[tditterline]

Several things can cause this , porous hose(s) on the intake side of the pump . A bad seal in the raw water pump can suck air , you may see a water leak there after shut down . And a issue with the vented loop .

I'll have too read up on the vented loop- not sure what you mean there. I guess I'll start with the main intake hose and go from there.

Can't be too hard, right??

Thanks for the reply!