OMC COBRA 4.3. BURNING MY HOSES. GETTING HOT

Pedrocasas

Seaman
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Apr 9, 2016
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This is my first boat. I did posted a topic about 1 month ago. I finally got to work on it.
So this what happen. The hose clamps that are holding down some type of big hard hoses, the clamp got really hot that it burned my red gas hose. As you can see on the photos.
The boat got hot. The smell of burning rubber when i went faster. Smoke from the hoses side. And from the outdrive.
I took a pic of the impeller
Picture of the red hose and the hose clamps.

Any ideas what it can or what causes this?

Thank you guys.
 

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Scott Danforth

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No photos.

My guess is there is zero water flow

Fix your raw water pump
 

Pedrocasas

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Pedrocasas

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Pedrocasas

Seaman
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So what I plan on doing today n tomorrow. Is remove the hoses. For that i believe you need to remove the risers. Also I removed the impeller. Water pump.

What else do I need to check and maybe replace? Thanks guys!!!!!
 

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bruceb58

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For that i believe you need to remove the risers!
Those manifolds are one piece manifolds so there are no risers.

Do you boat in salt water? If you do, check the outlet of the thermostat housing where the hose feeds the manifolds for corrosion obstruction.
 

Pedrocasas

Seaman
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Bruce. Sorry yea we got the names wrong. I do use salt water. I need to check the thermostat then. And the outlets. Thank you
 

bruceb58

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You are also going to need to check for blockage between the water pump and the thermostat. There is a power steering cooler between the drive and the thermostat housing. You may want to try back flushing from the thermostat back to the drive and make sure water comes out the water pump housing now that y.ou have the water pump apart.

So when does all this start happening? When you are in the water or when you are running on muffs?
 

Pedrocasas

Seaman
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Apr 9, 2016
Messages
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We took it out once. We just got the boat. Everyone was good. Untill the burning smell . Which was the rubber hose burning. I will start doing the flush tomorrow. And see if anything is blocking
 

Scott Danforth

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You have the dreaded bat wing manifolds. Change them now. They will kill your motor. Its not if they fail, its when they fail
 

bruceb58

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Agree with Scott. It could be that they are just all corroded up inside and preventing water flow. I would replace them no matter what.
 

Scott Danforth

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Just google bat wing manifolds....its what you have and what you need to replace
 

Lou C

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First off is your engine over heating, or only the exhsust system?
Engine temp on the dash gauge shoukd range from 160-175. If higher then you need to check/replsce the impeller in the upper gear housing and the thrtmostst housing and 'stat itself. If the boat was used in salt water extensively then the t stst housing and msnifolds are probably internally corroded and must be replaced. You can get the T stat housings but not those msnifolds. There are conversions to the later center riser style available . I had 3 sets of those bat wings on my salt water run boat; chsnged every 5 years never had a problem with them.
 

Bondo

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Ayuh,.... I also agree with Scott,...

As hot as ya got those manifolds, they're probably cracked inside by now,...
Even if they ain't, they're a known failure point, due to core shiftin' in the castin' process,...
 

Lou C

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Your impeller actually looks ok. The way to test it is to put the boat on the water and tie it up at the dock. Disconnect the hose that runs from the transom to the Thermo housing. Have someone start the engine very briefly (like a min or 2). You should see a stream of water shoot up at least 2" if it's good. If not replace it including the wear plate. Back flush the hose from the thermo housing to the transom mount while some watches the impeller mount area for good water flow. Next before replacing it take your water muffs and hook them up to the lower unit. Hold them tight to the water intakes and have some one turn on the water. You should see water come out of the other opening in the impeller mount. If not there could be a clog in the lower unit water intake area or water tube; or defective water tube gaskets. I had to clean barnacles out of mind lol!
If the thermo housing is all corroded buy a new one they are readily available.
There are conversion kits to convert your bat wings over to a 2 piece style like OMC and Volvo used on the later 4.3s, not cheap though.
Normal manifold temps on those manifolds should be:
85-100 *F at idle
125-135 *F max after coming off plane. This is what mine have always run at when all is right
 

Lou C

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PS the red hose that got scorched is not a hose; its your transom shift cable. If the boat does not shift easily this will have to be replaced.

To get those manifolds off:
Remove hose clsmps. Spray silicone spray on the Y pipe under the lower hoses. Pry around the upper part of the lower hoses that connect to the alu angled coupler piece and spray in silicone. Let it soak in. Then you have to slide the lower hoses down the Y pipe. Next remove the nuts that hold the manis on and they will come right off the head. They will not come off unless you slide those hoses off the coupler piece and down the Y pipe due to the manis being mounted on studs that go into the head.
 

Lou C

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Here is your pic, and how to get these off, once you slide the hose down, very easy.
If the hoses will not come off the aluminum coupler, get a small screwdriver and pry around where it fits on the coupler. You may have to replace these hoses anyway because they are probably scorched. When you have the manifolds off, look in the Y pipe for the exhaust flappers. They are a rubber valve that blocks water from coming back up the pipe. If these got really hot those rubber valves have melted I'm sure. They are easy to replace but you have to remove the outdrive to get the burnt up remains out of the bottom of the Y pipe..... OMC batwing.jpg
 

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Lou C

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OK last post on this subject....here is the OMC impeller mount so you can see what I'm talking about with the water flow.... Cobra impeller mount.jpg
 

Lou C

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water comes up from the lower unit on side marked in; and goes to the hose that leads to the thermo from side marked out
 
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