1994 OMC COBRA COOLING SYSTEM QUESTION

[HSBarker81]

Firstly, I'd like to thank everyone who has helped me with the questions i've posted in the past. Your responses have been timely and your information has generally been dead on...so now I bring you a new problem.<br /><br />My 1994 OMC COBRA 302 5.0 HO has been overheating on the port side manifold. I say overheating because the manifold gets much hotter than the other side and has even burned up my exhaust bellows. I believe I have the problem in sight and I want to ask your opinions...<br /><br />It seems that the flow is blocked somewhere down past the bellows. When we took the boat out yesterday, it began to heat up again. It caused a hole to burn in the bellow, but this let me to my conclusion. Once the hole was there, and the water was flowing into the bottom of the boat and out the bilge, the manifold stopped heating up and was fine for the rest of the trip. <br /><br />I previously tested a similar idea in my yard. When i put the rabbit ears on so that the water would flow into the starboard side of the lower unit, i could get water to come up from the lower pump hose at the thermostat housing...when i switched to port side, no water would come. <br /><br />What i'm trying to figure out now is whether or not the system drains seperately for each manifold or if they run together and come out as one. Either way, I'm 95% sure that something is causing the port side not to flow out of the boat. Any ideas?<br /><br />Thanks,<br />Harley

 

[Haut Medoc]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

Clogged riser at the water dump. Pull the riser and rod it out or replace it. If they are 11 years old they are due anyway (replacement), esp. if they are in salt water.....JK

 

[HSBarker81]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

if you mean the upper manifold pieces, then its not them....i have tested the flow of water through the manifold. my problem has to be below that last/lower exhaust bellow. maybe i've mistaken what you mean?<br /><br />-harley

 

[Boatin Bob]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

Not sure just what you are calling the "exhaust bellows", the bellows is actually down at the lower unit between it and the transom mount. If you are calling the rubber elbow that joins the riser to the Y pipe then inside the Y pipe there are flappers that prevent water from coming back up the Y pipe. Quite often these will fall off and end up? Maybe yours has fallen off and wedged in somewhere causing a blockage? Have a look at item 51 in this picture to see what I'm talking about. Flapper in Y pipe

 

[HSBarker81]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

yyyyyyyyyyyyessss... its that because when i was replacing the rubber elbow, i saw those little holes where the pin for that flapper go and i wondered what they were for...i'll post an update soon<br /><br />thanks guys

 

[HSBarker81]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

hmmm...so how do i get that ******* out? do i have to pull the whole y pipe off? and is that even possible without removing the motor?

 

[seahorse5]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

Don't overlook the possibility of the thermostat housing being restricted with deposits, expecially in the area where the manifold water hoses connect. On some models there is a bypass hole drilled inside the housing that plugs up very easily.

 

[rbezdon]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

HSB, if that flapper is down there it is not only stopping the water, it is stopping the exhaust too. My flapper was able to be pulled out through the exhaust bellows hole with the drive off.

 

[4.3sunbird]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

good thread ..I didnt know there were flaps in there <br /><br />guess I'll take a look at mine <br /><br />do you really need them? isnt the riser there to raise the exhaust high enough the water cant back up ??<br /><br />hey HSBarker81 you anywhere around Newport News ?

 

[rbezdon]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

4.3, the flappers are for the back wash after coming off of plane. The risers are good for static water intrusion but boats are active and so is the water around them. Also, if your docked and a big wake hits the back of the boat. Any moving water running up on the back of the boat can potentially create enough pressure to momentarily over come the static height of the risers. If the engine is off, then water intrudes into the manifold exhaust chamber and into any cylinder with an even slightly open exhaust valve. Then you hydrolock or worse. Flappers are one of those those things you dont need until you need them. They are a pain and a potential problem but most of the veterans here say keep em.

 

[4.3sunbird]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

makes sence<br /><br />I'll get a grip on this boat stuff one day <br /><br />I'm going to check mine out and atleast see that they are working freely<br /><br />I was thinking of thru transom exhaust but desided not to unless I put a v8 in the boat .. v6's just sound funny with open pipes

 

[HSBarker81]

Re: 1994 OMC COBRA COOLING SYSTEM QUESTION

Hey...yeah i live in Gloucester and I used to live in NN near Ft Eustis on Richneck.<br /><br />I know that it isn't the thermostat housing because:<br /><br />A) I replaced the housing and thermostat<br /><br />B) I tested to make sure water was flowing out of the riser on the upper end<br /><br />C) After the rubber elbow broke loose, the boat ran fine...because the water was flowing properly through the motor. Meaning that something is clogging up its exit passage. Not to mention the flapper is missing.