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Old 04-04-2010, 05:11   #1
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Honda Air-Cooled 2hp Outboard in Enclosed Space

I would like to decrease the noise level of my Honda 2hp outboard motor and I have been given two suggestions: 1. Find a better muffler. 2. Build an insulated enclosure around it.
Can anyone tell me if either of these solutions is practical?
Or, can anyone give me a reasonable solution?

Thanks,

Sid Breman
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Old 04-04-2010, 06:47   #2
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Greeting and welcome aboard the CF, Sid.

Is it one of those new fangled air-cooled four strokes?

I didn’t realize that they even had mufflers.

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Old 05-04-2010, 10:02   #3
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Honda Air Cooled

Yes, it is one of the new air cooled, 4 strokes and it may not have a muffler.
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Old 05-04-2010, 10:10   #4
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I was under the impression that is was exh through the hub.....don't know how you'd add a muffler to that.
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Old 05-04-2010, 10:57   #5
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It most probably exhaust under water Those motors a light weight but they are noisy I don't think there is much to be done except trade for a water cooled motor
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Old 05-04-2010, 11:24   #6
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It doesn't appear that it has a hub exhaust, rather an exhaust exiting just above the prop where a hydrofoil would normally exist. Not much you can do for the exhaust.
what could maybe be done is add dynomat or a comparable sound absorbtion butyl material to the inside of the cover, this should help some. on some engines sound can come from the intake of the motor, not much you can do about that either. Whatever you do don't block airflow.
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Old 05-04-2010, 11:31   #7
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Honda Air Cooled

Thanks, your responses have help. I'll try some sound absorbing material.

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Old 05-04-2010, 11:38   #8
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you will find there is not much room inside the cover for soundproofing material Maybe some thin lead sheet?
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Old 05-04-2010, 11:46   #9
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If you were to get the dynamat door kit (2sqft), the material is only 1/16 of an inch thick, I bet that will fit.
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Old 05-04-2010, 13:14   #10
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You don't want to build a full enclosure for your engine for several reasons. The engine is basically a big air pump which takes in clean air and exhausts air full of pollutants and you don't want to create a closed loop system for this air to travel, it won't run for very long.

If you overcame the intake and exhaust problem, you would be up against the engine overheating. Engines are designed so that they won't overheat until they operate at extreme temperatures which you would be creating with an enclosed box. At best, this engine might be 25% efficient with the remaining 75% being turned into heat that comes off the block and out the exhaust so you need to dissipate a lot of heat. It will run fine at first since it takes several minutes to get the block up to temp and then it will overheat if you put it in an enclosed space. To get around this, engine manufacturers have used water as a medium to transport heat away from the engine but since this engine is air cooled, that is not an option.

It would be possible to build an enclosed box but you would need to provide lots of airflow to it which takes power and provides a way for the sound to travel.

The ways that engines produce sound are through the exhaust, mechanical noises from the engine itself, and by vibrating its mounts. While hondas are pretty good, start by looking at isolating any vibrations from the engine by seeing how it is mounted. Since most of the noise comes out the exhaust, that is the next place to look. The noise coming out of the exhaust is very directional so you could consider extending the exhaust to point somewhere away from your vessel (and at the rest of us out sailing). You could also look at a different muffler but this often requires adjustments to the carb. A last option might be to kind of build a sound wall which didn't enclose the engine space but reflected noise away from the cockpit.
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Old 05-04-2010, 17:40   #11
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Honda Air Cooled

Fantastic. The sound wall is very feasable in my case. I'll try it. Thanks.

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