OMC cobra overheated/no water from exhaust?

[ajscobra]

Ok here is a quick run down. I have an 87 BaylinerCobra, 5.7, Cobra outdrive. I had the lower unit apart early this season for a gear swap and everything operated great?I have used it every weekend since the service.

This weekend was boating in shallow water had the trim raised and lowered it when depth permitted. Not long after the temp gauge hit 200 and I shut it down and got a tow in. Thinking I lost the impeller.

I pulled off the impeller housing and the impeller looked great. Fired the motor to verify the impeller shaft spinning, it was. Fed water to the drive with the muffs and the impeller housing still removed to flush/check flow and it looked good. Reassembled the housing and test ran the motor...no water flow from the exhaust (thru hull). Only a small weep from the weep hole on the impeller housing with strong water pressure.

Checked the water feed hose from the outdrive, no kinks. Removed the feed line at the t-stat housing and back flushed and gravity drained the line so that tells me there is no obstructions in the main cooling line. When I had the muffs on there was a lot of water coming from the front anode area...to my recall these drives are not sealed between the two halves?

So I know that even with a faulty thermostat I still should be getting water flow through the exhaust because the exhaust cooling lines are ran before the thermostat? Could it be the water passage tube in the outdrive that connects the two halves together?

Any ideas or areas to look at would be great...Thanks AJ

 

[cr2k]

Re: OMC cobra overheated/no water from exhaust?

Look real close at the housing and the cage in it. If this is not perfectly positioned straight you need a new housing kit.

I have seen several of these that look flawless but won't pump.

Were there any missing impeller blades? If so you need to look further in the system to find them ALL. i.e. heat exchanger, thermostat housing.

 

[ajscobra]

Re: OMC cobra overheated/no water from exhaust?

The cage that houses the impeller is not centered at all, and thus forcing the impeller blades to be somewhat compressed on one side, all the blades though are intact and still very much pliable. Just looking the housing I don?t think that it could have ever been centered in the cavity how I would think it would originally been intended to do. But even at that, with a perfectly functioning impeller shouldn?t I be getting some water from the exhaust with the hose and muffs?

Is there anything in the exhaust manifolds that may have melted and thus plugged them from flowing water...but both at the same time?

 

[cr2k]

Re: OMC cobra overheated/no water from exhaust?

It is not round, that is what pumps the water. But if it is not straight and even in the housing that could be your problem. The cage will get hot from running dry and soften the plastic housing. And it can **** clockwise as you look at it.
Also could be a stuck thermostat. Check this by dropping in water that was just boiled and see if it opens and closes after you pull it out.

 

[ajscobra]

Re: OMC cobra overheated/no water from exhaust?

Shouldn?t I still be getting water up through the exhaust even if the thermostat was stuck closed being the water lines that go to the exhaust are before the thermostat. As it appears to me the thermostat housing has a by pass to constantly cool the exhaust other wise nothing would cool down the exhaust until the motor reached 160 degrees or so to open the thermostat?