burning up exhaust hoses

[lpgreg]

I have a 1977 140 omc 4 cyl. ser.#990237e1. I have just burned thru 2 exhaust hoses where they exit out the exhaust manifold 90. Here is what I know. The thermostat is not the issue as I pulled it after burning the first hose, I am getting water from the impeller to the thermostat housing, when I removed the thermostat housing and started the engine for a few seconds water was backflowing from the exhaust manifold (maybe pressure from the exhaust stroke), when the hose burns up water is spraying out of it, there is no noise or leaks from the water pump, the engine runs fine, it only burns the hose at higher speeds, not trolling, and nothing is plugged from the impeller and back out the stern drive. Does any one have an idea on what to check first? Thanks Greg

[TerryKing]

Hmm.. The only thing cooling the hoses is the output water from the engine..

Do the hoses burn / damage evenly around? or just one side? Possibly the water outlet in the exhaust elbow is clogged with debris and spraying sideways??

Can you run it for a bit with the hose removed, into a bucket, and observe the water flow??

[lpgreg]

It is burning on just 1 side, I did remove the hose and started the motor and the water was coming out. But a lack of knowledge keeps me from knowing how well it is coming out.I removed the 90 that the hose attaches to, it is rusty but I did scrape it out.

[TerryKing]

Originally Posted by lpgreg

It is burning on just 1 side, I did remove the hose and started the motor and the water was coming out. But a lack of knowledge keeps me from knowing how well it is coming out.I removed the 90 that the hose attaches to, it is rusty but I did scrape it out.

The one-side burn makes it look like the water pattern being sprayed in is uneven. A 77 probably has significant rust in the exhaust elbow. Try to see the port or ports the water come out of into the exhaust.

Can someone who knows this engine / exhaust type help??

On some engines the water feed comes in a hose or line, and you can connect a garden hose to view what's happening..

The ones I DIY'd spray in 4 directions at right angle to the exhaust elbow and there's a pretty even spray over the inside of the exhaust hoses. Mine have lasted about 15 years...

Yours is probably built differently and you need someone who knows...

[lpgreg]

Terry
You might be on to something there, I will hook up the garden hose to the outdrive , disconnect the exhaust hose and check the spray pattern to see if one is more diminished then the others, then I will start the motor and compare that. Do you know of a rust remover that would clean this out? Thanks Greg

[charmc]

Terry's on the right track, I believe. You have one advantage; you can remove both hoses and compare the flow from each riser and manifold, which should help you pinpoint the location of the restriction.

There is some more information in the last post on this page: http://www.boatengine.net/t/053897.html

Muriatic acid will remove rust and scale. You can add a small amount to a plastic bucket filled with water. Be sure to use rubber gloves and eye protection. DO NOT add water to acid; always acid to water. You can get the acid and pH strips in a pool supply store or pool section of any large mart store. Get the pH to between 2 and 3, then soak the cast iron riser overnight. Rinse thoroughly and clean it up with a wire brush. Assuming it's the riser that was blocked and that it's not badly corroded, this might give you a few years more life before replacing the riser.

[lpgreg]

Thanks for the info and the link, it looks promising. Greg

[stonebreaker]

Try electrolytic cleaning. It's a lot safer than fooling around with that acid, it's cheap, and best of all you don't have to scrub.

http://www3.telus.net/public/aschoep...lyticrust.html
http://www.bhi.co.uk/hints/rust.htm

[lpgreg]

I,m in the process of the electrolyic cleaning now. It is eating up the rust using baking soda,It might take a day or 2 and then put it back together. I,ll keep you all advised. Greg

[mongo75]

I've used muriatic acid before, but I really like that electrolytic method- please keep us informed!

[lpgreg]

Well its still overheating but was worth a shot thanks for all the help. Greg