Anti-vibration pads

[Graham W]

Continuing with the rubberised theme started by Matthew (beach rollers), has anyone tried isolating their outboard clamps with anti-vibration pads?  The idea being to reduce the amount of vibration and noise transmitted by the outboard through the transom mount to the rest of the hull.  The pads would need to be mounted on both sides of the transom clamp and, because the upper part of the clamp rests on the transom, probably over the top as well.

In an ideal world, pads fashioned from Linatex natural rubber sheet might be best but unless you're in the extractive industries or tend to horses professionally, a small amount is difficult (or even impossible) to come by.  Has anyone tried anything else?

I was complaining about my Torqeedo 1003's noisy whine on another forum the other day.  Someone suggested that part of the problem (other than the issue with the over-large motor mentioned elsewhere) could be resonance caused by the way the motor is mounted in the boat.  Is it possible that the BR outboard well acts as a sort of loudspeaker?  If so, isolating the motor from the rest of the boat might help.  Likewise filling the outboard well with ping pong balls (only kidding).  The Torqeedo doesn't vibrate much but my Mariner 6hp definitely does.

[Peter Cockerton]

Graham

The securing pads would also need isolating from the transom to limit vibration onto the transom, not sure if winding them down onto a rubber giving surface would provide the grip to hold the engine in dare i say it a T***le situation.

Could probably consider isolating the transom from the hull with rubber mountings though.

The noise makes you want to sail and shut the engine down as soon as possible don,t you think.

Peter

[Rob Johnstone]

I'm not sure that the noise is transmitted through the outboard mount. My impression is that the sound of the motor echoes off the sides and ends of the well. It might be worth experimenting with some rubber or polystyrene foam glued to the sides. I'll let you know in the spring!

Rob J

[Peter Taylor]

I've long thought that having the outboard in a well does concentrate sound in the cockpit. My 6hp Tohatsu seems loud on board Seatern but if a walk back to the shore end of the jetty (only about 7m) it can hardly be heard. Most sound proofing materials are designed to stop transmission of sound through them. To stop sound being reflected you normally use a porous material like open cell foam. Unfortunately another name for that would be a sponge - it will absorb water as well as sound!

Some acoustic panels are like a modern variation on peg board ( which used to be, and may still be, used for sound absorption ). Lining the outboard well with that might work but ideally you would want a gap behind it of order few cm or much more since we are worried about low frequencies. Seatern's outboard well is small enough already!

Stopping transmission of vibration from the outboard (which might be making the well sides vibrate) seems worth a try. There's some pads called Vibra-stop. This video uses a Tohatsu "just like wot I have":

Youtube: https://youtu.be/gA3TwYD-Vas 
apparently Vibra-stop is made in New Zealand  http://marinexpress.co.nz/shop/vibrastop.html

I've emailed NZ re availability in the UK, from their web site it looks like cost would be order £100 or more if you have to pay import duty, my quick search didn't find a UK source. Awaiting reply.

Peter

[Peter Taylor]

Well, last autumn I got the Vibra-stop pads from New Zealand (cost about £116) and last week managed to get around to fitting them. Sadly they produced no improvement to the sound levels at all. If there was any change it was that the sound was slightly louder (order 2dB) in reverse!

The sound measurements I did are on my Seatern blog for March ( http://www.seatern.org.uk/SeaternDiaries/diary_2017_mar.php and look at 15th March) but they are not really worth looking at! My conclusion is that the pads might work for something like an aluminium workboat (as in the YouTube video). There the outboard is mounted on a metal transom which could set up resonances. Probably the small outboard mount in Seatern is too rigid to be transmitting much sound. It seems to confirm Rob's impression that the noise is due to echoes off the sides of the outboard well.

Anyway, I've saved you all £116 and the effort of fitting the things!

Peter

[Graham W]

If Rob is correct, then perhaps something like this inflatable cushion stuck to each side of the outboard well might help? https://www.completecareshop.co.uk/bathing-aids/bath-cushions-and-pillows/inflatable-bath-cushion-view-large?gclid=CKCKtLaL7dICFaMK0wodBbsLJQ