Anyone have designs/ideas for a hush box?

[DaveC426913]

I'm going power cruising in the spring. Canals are limited to 5mph. It'll be a lot more pleasant for 6 hours of cruising per day if the motor is quiet.

Has anyone designed or built a 'hushbox'? Some sort of baffle to quiet the sound of the motor in the cockpit?

If not, does anyone have general acoustics suggestions about the most effective way to it?
- what shape, how much coverage is enough
- what materials

I've got a Honda BF50.

[DaveC426913]

Oh, and to stave off the obvious replies, as in this thread: http://www.macgregorsailors.com/phpBB/v ... 62&start=0:

No - sound-cancelling headphones are not the way I want to spend my week cruising.

[Kittiwake]

.... limited to 5mph ..... Has anyone designed or built a 'hushbox'? Some sort of baffle to quiet the sound of the motor in the cockpit? ......

As I recall, a few months ago on this site someone mentioned that a big empty plastic storage tote placed under the rear (hinged) seat achieved some significant engine-noise suppression. I have the so-far-untested-but-maybe-logical impression that the engine noise at low speed is more subdued when the ballast tank is filled (ie. so that the engine exhaust exits farther below the surface).

[Tomfoolery]

I would guess that erecting a wall would significantly reduce noise in the cockpit, and the plastic tub is just that. Something between the helmsman's ears and the OB should also help greatly, wide enough that most of the sound won't 'bend' around it. Like closing a car window when next to a noisy car, or even putting your hand between your ear and a noise source (but bigger is better). Louder behind the boat, but you're not driving from back there.

Additional soundproofing inside the cowl seems to have a significant effect, according to posts in your link, so a combo of both mechanical barrier and 'sound-proofing' the cowl I would think should result in a much quieter ride.

[NiceAft]

I don't understand. That four stroke motor is extremely quiet, unless you go close to full throttle, and that will have you going considerably faster than 5mph,


Ray

[mastreb]

The most effective place to put sound dampening foam on a boat is directly inside your ear canals These are also effective against human sources of noise such as my kids

The problem you're going to have is that the motor is hard mounted to the transom, which means that while you could wrap the motor in an acoustic foam to dampen direct engine noise, the boat still vibrates and generates noise. For example, my cockpit hatches and helm seat vibrate and are quite noisy.

I would use 1/2" acoustic dampening foam inside a secondary hard box that simply sits over the motor cowl and is strapped to it. You might see if you could fit the foam inside your cowl, but the MFRs generally have as much noise dampening foam inside the cowl that will fit these days.

I would also put small strips of the stuff under the cockpit hatches and the helm seat (both sides!) to eliminate the vibration noise from those sources. Also maybe put some rubber or plastic o-ring bushings in the joints of the stock steering assembly to eliminate "jingle" there.

[NiceAft]

And what do you recommend to offset the noise of the engine echoing off canal walls or close by objects.

When I was first married, my wife and I lived in an apartment close to the Reading Railroad tracks. Yes, the same as in Monopoly's “Take a ride on the Reading” After a few days we slept right through the one AM freight. Don't worry about any engine noise, after a short while, you won't even notice it.

Ray

[Québec 1]

I hâve à Honda Bf 50 and i cannot hear it at the bow when on low rpm. Maybe there is some kind of problem with your motor.

[133bhp]

THE PO biult a thin plywood wall the shape of the area when the seat is down on an X, clips in, it does work, probabaly 30% reduction. I mean to try a dense rubber/foam liner inside the motor cover one day also

[Boblee]

THE PO biult a thin plywood wall the shape of the area when the seat is down on an X, clips in, it does work, probabaly 30% reduction. I mean to try a dense rubber/foam liner inside the motor cover one day also

I guess that would help but I really can't see the problem especially with a Honda which is much quieter than a two stroke, Mastreb suggested ear plugs and that will cut out all loud noise but this is not loud noise especially at 1000-max 1500rpm.
We did find that when had the power thruster on it pushed the exhaust gas underwater further out and suppressed the noise better but you will still have some noise bouncing off the channel walls depending on material and height?
I can't say I have ever noticed the noise at low speeds, high speeds definitely.

[yukonbob]

9/10 times when I'm casting off with guests they ask quite worriedly if I'm gonna start the engine before I untie…then I inform them its been running for fifteen min. Suz DF70

[Chinook]

Lower rpm is my best way of reducing engine noise. We've also noticed that, with the bimini up and the rear panel of our cockpit surround left in place, noise levels from the engine are noticeably reduced.

[NiceAft]

J--,

I don't believe anyone has asked if you have boated at 5MPH for any length of time. If yes, was the Honda too loud for comfortable boating

Ray

[Tomfoolery]

I run at 5 mph in the Erie Canal all the time, for extended periods. The BF50 doesn't make much noise, IMO, and conversation isn't impeded at all. But I can see where the OP might want to knock it down a little more - sort of the difference between small a Chevy and a big Cadillac as far as quiet driving goes. I too have noticed the sound reduction when using the full enclosure, which blocks higher frequencies, even though it's only thin material and plastic. Closing the hole under the seat (I have a Sunbrella panel for that) and either a shield (small and cheap) or sound-absorbing lining inside the engine cowl (also small and cheap) should help, though that won't cut any exhaust noise.

[dlandersson]

Perhaps thinking outside the "box" - get a electric outboard (Minne-Kota, etc.).

I'm going power cruising in the spring. Canals are limited to 5mph. It'll be a lot more pleasant for 6 hours of cruising per day if the motor is quiet.

Has anyone designed or built a 'hushbox'? Some sort of baffle to quiet the sound of the motor in the cockpit?

If not, does anyone have general acoustics suggestions about the most effective way to it?
- what shape, how much coverage is enough
- what materials

I've got a Honda BF50.