OMC Cobra overheat at idle, new impeller, no blockage

[Paul.v]

I know, another overheat issue. I've read all the posts. Mine is 1989 5.7L. It has overheated at low speed or idle since i replaced the drive 2 years ago. could not figure out why but reading the posts leads me to believe its the pickup tube. I put a new impeller in, old one looked heated & small chunks missing. I backflushed the system from the T-stat. Still overheated, so I got some clear hose(Bondo's idea) and put at T-stat input. On initial startup no water for 30 seconds untill i reved to 2000, thena gush of water & continued flowing at idle but with dime sizebubbles.....I'm thinking bad seal on pick up tube....agree? If so, what gaskets do I need? Full kit? or just water tube seals,drive shaft O rings, and housing gasket? Drive has 150 hrs on it.....Thanks for your input! Paul

 

[PaJon]

Pull the power steering cooler off and make sure it has no blockages.

 

[Idlespeedonly]

I wouldnt order anything until you have it tore apart. But if pressed for time i would get the water tube seals(possibly even the water tube),drive shaft O rings, housing gasket and another impeller, liner, wear plate and o-ring(for a spare). Also, more oil.

 

[Paul.v]

Pull the power steering cooler off and make sure it has no blockages.

Thanks, I did that prior to putting in new impeller, was clear and I back flushed.

 

[Paul.v]

I wouldnt order anything until you have it tore apart. But if pressed for time i would get the water tube seals(possibly even the water tube),drive shaft O rings, housing gasket and another impeller, liner, wear plate and o-ring(for a spare). Also, more oil.

Thanks, I can use boat as long as I prime pump immediately so I dont want to have boat laid up while I wait for parts...Thanks for your list, thats what I was thinking just wasnt sure if I was overlooking anything. Im on call the weekend of July 25th(cant go boating) so Ill get parts for then & tear it down. Ill post what I find.
Thanks!

 

[Bulbash]

I had similar issues and replacing seals on the lower water tube did fix it. Now no more overheating on idle... You will need outdrive gasket set P/N 508105 and water tube seals P/N 911705

 

[Paul.v]

Awesome! thanks for the part #'s!

 

[Paul.v]

Just a follow up . Rebuilt drive, pick up tube seals were ok but gaskets at top were original & sucking air. Replaced everything on the water pickup, re sealed. No more overheat! I left clear tube at engine, I like the quick visual check . All good for 4 years now! Thanks guys!

 

[stang32]

thanks for the follow up, so many posts just fade away leaving others to wonder, what the heck happened? how was this issue resolved.

 

[Lou C]

Agreed the follow up is what really helps others

 

[GA_Boater]

Thanks for the update. :thumb:

 

[Paul.v]

thanks for the follow up, so many posts just fade away leaving others to wonder, what the heck happened? how was this issue resolved.

I had to separate the top & bottom drive & install all new seals although the problem gasket was in the top drive where the pickup tube comes through. It was obvious the "rebuilders" chose to leave it. It was a problem from day one, always difficult to prime. Clear tube at Tstat input really helped me see all the air coming in & decide to pull the drive. The job ofe reasealing wasnt that bad to do.