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How do I fit a new exhaust hose?

2009 April 1

Dear Boat Doctor,
I have a Farymann one-cylinder, 9-horsepower diesel and a newer muffler on my 1978 Tartan 10. Last summer I discovered (after replacing the water pump impeller and noting the water gushing while the engine was running) a loose exhaust hose. I was able to crank down the hose clamps to stop the flow, but noted that the clamp was crushing the hose. This was fine for the rest of the season, but now it's time to see if there is a better solution.
The manifold end fitting is about 1-9/16 inches (the Farymann, of course, is German, so maybe it's metric) and the muffler end fitting is about 1-11/16 inches, so a constant-diameter hose obviously has to be distorted at one end or the other. The hose is only 12 inches long.

It seems to me there are three solutions and I'd be interested in your opinion on each:

1. Find some sort of custom hose in the right size, like an automobile radiator hose, which may be very difficult and time consuming.

2. Refit a new, constant-diameter hose, as close to the muffler end ID as possible and clamp the manifold end tight, as before.

3. Try to plumb using some sort of reducer in the middle. This would be more elegant in terms of right sizing, but would add a set of hose clamps, reduce ID in the reducer by the thickness of the material, would reduce flexibility and parts might be just as hard to find as a custom hose.

Dave Brezina
Chicago, Illinois

Dear Dave,
Marine plumbing can be frustrating, throwing in a mixture of standard and metric hardware makes it that much worse. The ideal situation would be a custom hose designed for marine use, but I suspect that would be very difficult, if not impossible, to find.

I agree that some sort of reducer would not be ideal in the short run of hose; the loss of flexibility would be a risk. I would try to better implement what you already have. I'd start with a new section of hose. Get the best hose you can; it will be expensive but you don't need much. Secure the hose with top-quality hose clamps, double clamped. Depending on the length of the hose barbs that you are attaching to, you may be able to use a T-bolt band clamp. These clamps tighten more evenly and with much greater force.