4,3 OMC cobra overheating exhaust problem. I need Help

[Carlos Moreno]

Hello, I Have a 4,3 OMC cobra , 1993 model.

The first is that I live in Colombia, we speek spanish, and excuse me for my English.I try to do my best,

I have a problem with the exhaust, once start the engine, the exhaust elbow turns overheat, burning the exhaust hoses. I think this is not normall.

I change the impeller( its new), and the hose that bring water until the thermostat.

Is possible that the manifolds and the elbows are blocked by rust ?
How I know if I need to change it ? Its possible to repair, How ?

Thanks

 

[Don S]

Re: 4,3 OMC cobra overheating exhaust problem. I need Help

Is possible that the manifolds and the elbows are blocked by rust ?

It's very possible tht the manifolds and/or the elbows are plugged up and causing your overheat. Just remove the risers (elbows) and look at the passages. Also look at the opening in the end of the risers where they attach to the exhaust hoses.

Before you take it apart. Locate the hose that goes from the transom shield to the thermostat housing. Disconnect it from the thermostat housing and with water to the drive with muffs, see if water comes out of the disconnected hose when you start the engine. Should be a very good flow of water. If not, you have a pump problem.

 

[Mach 1 Spitfire]

Re: 4,3 OMC cobra overheating exhaust problem. I need Help

Carlos,
Did you play with the ignition timing? If so, retarded timing can causes the exhaust to get very hot
Doug

 

[jerryjerry05]

Re: 4,3 OMC cobra overheating exhaust problem. I need Help

If the impeller is new and the manifold /riser gets hot then the Riser is probably clogged.Jerry

 

[Lodgepole]

Re: 4,3 OMC cobra overheating exhaust problem. I need Help

I had a 1992 3.0 cobra that got hot and it was the flapper that hangs in the exhaust just below the boot that connects the riser with the exhaust pipe going to the drive unit had burned off the pivot pin and dropped down and blocked the the exhaust where it goes into the drive. You might check this.

 

[Carlos Moreno]

Re: 4,3 OMC cobra overheating exhaust problem. I need Help

It's very possible tht the manifolds and/or the elbows are plugged up and causing your overheat. Just remove the risers (elbows) and look at the passages. Also look at the opening in the end of the risers where they attach to the exhaust hoses.

Before you take it apart. Locate the hose that goes from the transom shield to the thermostat housing. Disconnect it from the thermostat housing and with water to the drive with muffs, see if water comes out of the disconnected hose when you start the engine. Should be a very good flow of water. If not, you have a pump problem.

Don, thank you very much. What means good flow? How I can measure a good flow, because it could be subjetive. Its possible to know a Qty of water that the House should throw out ?. I mean , for example: 5 Liters /minute, ...

 

[Carlos Moreno]

Re: 4,3 OMC cobra overheating exhaust problem. I need Help

I had a 1992 3.0 cobra that got hot and it was the flapper that hangs in the exhaust just below the boot that connects the riser with the exhaust pipe going to the drive unit had burned off the pivot pin and dropped down and blocked the the exhaust where it goes into the drive. You might check this.

Thanks for your interest. In fact the flappers were burned. I had changed both.

Carlos

 

[chiefalen]

Re: 4,3 OMC cobra overheating exhaust problem. I need Help

You found the pieces of the flapper??

They sometimes fall down and block the water passage.

But still Carlos the risers might me clogged up. Hows that look??

You have any heat exchanger on the boat?? They get clogged up also.

Good luck amigo hope it works out for you !