OMC Cobra low rpm overheat issue cause found finally!

[AlphaJustin]

Hey guys, I've been bouncing back and forth between clymers and the official shop manual and the forums for ideas there have been tons but none are the same as my issue turned out to be so figured I'd mention this.

I rebuilt the outdrive last winter went great got it all done and sealed pressure tested fine used it a couple times no water in the oil fantastic since then I've been having a low rpm overheat issue replaced the upper water pump rechecked and sealed the drive impeller and all clamps to no avail so pulled the drive again.

I found the leak it's at the top of the water uptake tube between the upper and lower unit so out of the water it spits excess water out between the two halves and in the water the impeller sucks more air than water. There's nothing in the manual about it almost like it's unimportant so I breezed over it there's no seals no orings nothing just "make sure they connect" and good to go well it seems it takes more effort than that.

So if your having a low rpm overheat issue and can't find it, hook up the hose and watch to make sure water doesn't leak out from around the anode on the front of the case if it does your drive isn't together right like mine and you need to split it and get the water uptake tube to connect and seal properly.

Hope this helps other people with another thing to check when having this issue good luck all.

 

[MRS]

Alpha, good information I mightt have to check mine stays in the range but does take awhile to get there sometimes. Starts to climb around 180 then will drop Thanks..

 

[Lou C]

Hey guys, I've been bouncing back and forth between clymers and the official shop manual and the forums for ideas there have been tons but none are the same as my issue turned out to be so figured I'd mention this.

I rebuilt the outdrive last winter went great got it all done and sealed pressure tested fine used it a couple times no water in the oil fantastic since then I've been having a low rpm overheat issue replaced the upper water pump rechecked and sealed the drive impeller and all clamps to no avail so pulled the drive again.

I found the leak it's at the top of the water uptake tube between the upper and lower unit so out of the water it spits excess water out between the two halves and in the water the impeller sucks more air than water. There's nothing in the manual about it almost like it's unimportant so I breezed over it there's no seals no orings nothing just "make sure they connect" and good to go well it seems it takes more effort than that.

So if your having a low rpm overheat issue and can't find it, hook up the hose and watch to make sure water doesn't leak out from around the anode on the front of the case if it does your drive isn't together right like mine and you need to split it and get the water uptake tube to connect and seal properly.

Hope this helps other people with another thing to check when having this issue good luck all.

Which manual are you referring to? Because in the factory shop manual it shows the upper and lower water tube gaskets and there is a guide for the lower one. You install the gaskets; then install the plastic guide on the lower one. Now push the water tube into the upper gasket. Then when you install the upper onto the lower; aim the tube at the guide and it will allow the tube to seat perfectly in the lower gasket. I've done it this way 2x and never had a problem...

 

[AlphaJustin]

Which manual are you referring to?

Lou, I had been working off the Clymers when I did the drive. I recently got the official manual and it's more detailed but still the same where it implies they just go together and seal but if you end up unlucky like me your upper seal can unseat itself during the install (just old and didn't stick together) and you end up with a small barely noticable leak at the top of the uptake tube that's just enough to let air in at low rpm.

MRS good luck maybe you'll find yours in there even the smallest separation or cracks in those rubbery guides/seals can let enough air in to cause a slight overheat. Sitting in the water idling the connection is submerged at low rpm it's high enough to pull air and at WOT it has enough force to suck enough water and air to cool the engine.

 

[Scott Danforth]

Clymer and seloc manuals work as knee pads, not a service manual

 

[HT32BSX115]

Clymer and seloc manuals work as knee pads, not a service manual

Pretty good material for starting woodstoves too!:thumb: