A muffler question

[Keith]

This maybe a silly question or thought but...

My son and I were talking about fuel consumption and how to get the most bang for your fuel buck. He asked would it help if we removed the mufflers from the exhaust system and let the engines 'breathe' easier? Hmmm - sounds like a good idea, don't they remove the mufflers from race engines? Does the removal of the mufflers give more horse power, better fuel economy or what?

Our boat has 8V71 naturals.

Keith
Lady J

[MikeP]

No, unless the mufflers are damaged/rotting internally, it will not help to remove them. There is no power increase associated with removing mufflers on any vehicle AS LONG AS the mufflers are in good condition and properly sized for the engine.

The idea that removing mufflers or putting "less restrictive" mufflers adds performance has been around for a long time but OBJECTIVE dyno tests, not those published by people who are trying to sell mufflers/exhaust systems, have consistently shown no improvement and sometimes a DIS-Improvement by installing a "high performance" muffler or removing a muffler completely.

A muffler COULD be added to any race car and not reduce power BUT it would have to be fairly large and would add weight/volume that would be difficult to accomodate in the current design of the cars.

These boats are noisy enough WITH mufflers - I can't imagine you could stand being in one for long with NO mufflers!

[Bill Allen]

After I repowered my Topaz 3208's to John Deeres the mufflers were removed as the installers did not like the back pressure. We put in check valves. The noise at the dock off the bulkhead is actually less then my hatts 6-71's need to remember the JD's are turboed which helps noise levels. Never heard them running hard but I don't believe them to be as loud as the hatt at any rpm. Of course the fact I think DD have a beautiful tone might be part of my perception.

[REBrueckner]

I agree with Mike P...it's a lot more trouble than it's worth....
the best way to save fuel money is go slow....

If you boat every weekend for example, you can consider instead taking a three day weekend on alternate weeks...that cuts typical fuel use in half....then you can read Sam's here on the "off" weekends"...but you'll likely notice more crud accumulates on your drivetrain and bottom...

[Keith]

OK - well I guess I won't be installing Flow-Masters on my engines....

We do cruise at slower speeds to conserve fuel usually between 8 and 10 knots depending on the sea conditions. I mainly asked the question because we are planning on cruising to Alaska from San Francisco in the next year and was just exploring options.

Thanks for the input.

Keith
Lady J

[GaryNW]

The key is to not exceed your true hull speed. I see a lot of wishfull thinking on hull speed, including on the HOF. If no flowscans, then I would use square root of LWL x 1.3. So one needs a LWL of 56' for 10 kts. Pushing even a little over the limit (say .25 kt) will have a dramatic effect on fuel consumption.

I note that Hatteras does not publish their LWL. I imagine it's because they are planning boats. Measure it yourself, then you will really know.

That should be a great trip. Keep the mufflers so you can still hear once you get to Ak.
Gary

[MikeP]

Hatt does publish LWL, at least they did for our 53MY. It's in the owners manual that came with the boat but I can't remember at the moment whether it's listed in the specs in the front or shown on the blueprint diagram. But it's there somewhere. I can't check the specific location since that material is on the boat but I remember that it shows our 1980 53MY having a lwl of 47' 8"

[GaryNW]

I stand corrected! Seems that Hatt must have published LWL for some models and not others. They did not for my 1975 31' EC. All other data is under "HULL", "Construction", "Principle dimensions".
Gary

[NAN-PO 41]

When we bought our boat it had rubber Salisbury mufflers. I thought it was pretty loud at the time. (8v53n's) On our way home from a trip the seam on one split open. (thank God for high bilge water alarms if you don't have them all I can say is install 2, one fwd and one aft) I took out the mufflers and put in a fiberglass pipe until we could decide what mufflers to get. The increase in the noise level was incredible. You would get a headache on the flying bridge. We installed aqualift mufflers and the difference is nothing short of miraculous. I love the sound of a Detroit but without a muffler they make the boat virtually unusable. KEEP THE MUFFLERS!!! If anyone is thinking about replacing their mufflers they should seriously consider the waterlift type. Physical size is much smaller and they really work well.
JMHO, Fred