To loop or not to loop???

[Seashantyman]

My 1979 O'Day 28 has a 1 5/8 exhaust hose, about 12 feet of it, which has a vertical loop in it before it exits the transom... this, I'm told, is to keep water from siphoning back into the exhaust, in case the stern were to squat for whatever reason. The survey I had done when I bought the boat seems to disagree with this. Number 1, he called it the "Fuel vent hose", and number 2, he said to reroute it to get rid of the loop as the loop may trap fuel in it...??? Now, I do know that this is indeed an exhaust hose, and I can't imagine how fuel could ever get into it, so is this just a case of a surveyor that got a bit confused while lying upside down in my engine room??? Anyone else out there have, or not have, an exhaust loop? Any info would be appreciated as I have to upgrade this hose and it is a bit costly.... so buying 8' of it rather than 12' would save me about $60.00. Thanks in advance!

 

[Don Evans]

Yikes

Sorry mate, but if this marine surveyor can confuse a marine exhaust hose with a fuel vent hose what else has he got wrong? Thats nonsense. Thank god for owner vigilence. Anyways, you are describing a proper exhaust system. Indeed the loop or inverted U is raised above the boat's waterline and breaks any backflow that could develop because of the low position of the engine. Some systems incorporate a goose-neck device at the transom, in place of the loop, to prevent the entry of seawater. You say the hose needs replacing? If the hoses look stiff and sound and all the hoseclamps are holding tight, you should be fine with your current exhaust system. I would not trust the surveyors word at this point. Get a second opinion from a trusted marine mechanic. Do check the condition of your mixing elbow for signs of corrosion. This is a common problem and needs to be replaced if any is found. Don

 

[lnranch]

Loop is Correct

I also have a O'Day 28 and I agree with Don. All surveyors are not created equal.Good Luck you have a great boat

 

[SeaShantyMan]

re:Loop or not to loop

Thanks Don and Inranch.... appreciate the info. Glad to know that the exhaust system IS properly set up. It sure looked logical to me. I have to confess that I don't know what the 'mixing elbow' is though Don??(My first inboard engine!)

 

[Don Evans]

The Mixing Elbow

is the portion of the exhaust where the water is injected just aft of the manifold. Basically its heavy galvanized iron , usually a short piece angled down (like an elbow)and its what connects the manifold/block to your exhaust hose. Called a mixing elbow because the water from the engine jacket is mixed with the exhaust gases.It can corrode because the slightly acidic nature of exhaust gas, mixes with salt/fresh water. It is also susceptable to coking/carbon buildup and mineral deposits, restricting exhaust passages through the elbow. Its usually the first part of the exhaust to need replacing and it can be difficult to remove if the bolts are corroded. Remove the exhaust hose at the elbow and have a good look inside. These can be cleaned if badly fouled, but will need to be replaced if any corrosion is evident.Don

 

[Art]

loop in hose

What you're surveyor told you is true. I think you are looking at the wrong hose.A fuel vent hose goes from the top of your fuel tank to a vent fitting in the hull usually high on the freeboard on or near the stern. It's typically 1/2".A full loop (coil) in this hose (as was the on my O'Day 34) will get filled if you overfill the tank and prevent it from letting air into and out of the tank when you use fuel or add fuel.You should have the hose "loop" higher than to vent fitting to prevent water from getting into the fuel tank.