why are four stroke outboards so noisy?

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herdman

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having owned 2 stroke and four stroke outboards i have been surprised by how load the 4 strokes are. I currently have a mariner 4hp 4 stroke and a honda 2.3hp 4 stroke. they both seem more noisy than my mercury 3.3 2 stroke. what i am really looking for is a 5 or 6 horse power outboard that weights 25kg or less and is QUIET - does anyone have any views??? I thought i saw a yamaha go past that didn't seem too bad but it was not being revved v hard - any ideas gratefully received (i was thinking about a mercury 5hp 2 stroke but i suspect they are all out of stock...)
thanks
 
Suzuki 5HP, a lot quiter than my old 3.3 HP Malta and has te advantage of being able to use either its own intergrated tank or an external one.
 
I had a Yamaha 4 stroke 4HP which was a lot quieter thn the Honda 5HP I had previously.
I think it's as much to do with pitch (sound, not propeller) and vibration as actual volume.
 
I don't think that four strokes are inherently noisy. Listen to a Yamaha 6 or 8 and you will see how quiet they can be. Unfortunately they are much heavier that the Mercury/Mariner/Tohatsu and Suzuki 4 to 6 HP singles that have the weight you seek.

On your Mariner 4hp, check that there is no looseness in the bolt through the mounting bracket. The big horizontal bolt that the motor tilts up on. Looseness here can cause noisy vibration.
 
The noise is different! Small four strokes sound clattery, like lawn mowers - basically the additional moving parts in the valves make a noise, whereas a two stroke sounds more from the exhaust. Personally I think the nicest sounding small outboard is the Evinrude twin - a two stroke, but very smooth when firing sweetly. The Honda 2.3HP sounds just like a lawn mower - probably because it shares the same heritage? I have recently bought a four stroke 2.5hp Suzuki - for a four stroker it is really not too bad for noise, and on tick over/low revs is very quiet.
 
Spent Saturday night on the mooring (on the main channel in the Hamble), so the chance to evaluate all sorts of engine noise from proper boats, motorboats and tenderised outboards. Nothing was as noisy as an old Seagull, not even the gin palaces with hot and cold running jacuzzii.
 
[ QUOTE ]
Nothing was as noisy as an old Seagull

[/ QUOTE ] Noise is unwanted sound. A Seagull makes music!
 
[ QUOTE ]
[ QUOTE ]
Nothing was as noisy as an old Seagull

[/ QUOTE ] Noise is unwanted sound. A Seagull makes music!

[/ QUOTE ]

You must be tone deaf! /forums/images/graemlins/tongue.gif /forums/images/graemlins/grin.gif
 
[ QUOTE ]
Not to my ears. A loud metallic rasp accompanied by a lingering smell of half-burnt oil.

[/ QUOTE ]

Better not go to the Isle of Man this week. /forums/images/graemlins/cool.gif
 
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