Why are some stinkpots much louder than others?

[fredrussell]

I wondered if it was something to do with engine type. I think some of them are petrol powered - does that make a difference?

 

[oldgit]

I wondered if it was something to do with engine type. I think some of them are petrol powered - does that make a difference?

Small petrols tend to be much quieter than any diesel but there is definately something about the sound of a pair of big V8 petrols in a fast sport boat going past.
Just glad the owner is filling the tank.

 

[Beelzebub]

Even I don’t like to be disturbed by a noisy engine....but try spending a windy night or week in harbour with the infernal rattling of hundreds of yachts 24 hours a day

A valid point and the stupid thing is that it costs nothing to prevent it. Clearly the owners of these boats have never slept aboard.

 

[Snowgoose-1]

Some years back now but some yachts used to be fitted with an air cooled inboard diesel. Petter 7hp ? .Tranona would know. Much louder than any mobo.

 

[Snowgoose-1]

Small petrols tend to be much quieter than any diesel but there is definately something about the sound of a pair of big V8 petrols in a fast sport boat going past.
Just glad the owner is filling the tank.

A chap was fitting some kitchen units recently. When he pulled up in a Volkswagen I commented that it sounded like a V8. He said it was not the car but a recording. I had know idea you could buy things like that.

 

[Elessar]

I wondered if it was something to do with engine type. I think some of them are petrol powered - does that make a difference?

It’s all about the exhaust.

The very noisy boats tend to be race boats. Two v8 petrols of 7-8litres each and no silencer at all just 4 pipes straight out of the transom.

It would be completely illegal on the road.

I took such a vessel out of port solent for a magazine shoot. The noise in the lock was incredible. Engines off as soon as I could.

Just as the gates were shutting they opened again and a little westerly with two elderly couples on board came into the lock. The two ladies were on the foredeck.

I spoke to them to apologise in advance, and to warn them that when the engines were started the noise would be outrageous.

Their reaction when the engines started with an explosion type noise was not what I expected - they laughed so much I was worried they may have wet themselves

 

[Rappey]

A couple of lads had a cheap inflatible and a chinese strimmer type outboard. It was very noisy and maybe 1hp? Could be hard miles away.

 

[38mess]

My mobo has a straight through exhaust, it's only a 30 hp diesel and I have been told it sounds quite pleasant. But when underway the exit is underwater, so all we can hear is a slight burble

 

[scottie]

I mean no disrespect to mobo owners, but why are some of them so loud compared to others? On the Orwell yesterday there was one that you could hear, easily, two miles away. It’s hard to believe their owners actually want it that way. I can’t understand how one boat with several hundred hp can make a fraction of the noise of another similarly powered one. Is it just different exhaust systems?

If no disrespect intended then call them motorboats
yes it’s different exhaust systems mainly

 

[PetiteFleur]

At Halfpenny Pier on Sunday and the small motorboat behind us, about 18' long, had a totally unsilenced exhaust - it was really loud, perhaps the crew just don't hear it? I have a water trap, muffler and swan neck on our 25hp Beta and from the outside you can barely hear the exhaust - just a gurgling from the exhaust water.

 

[Farmer Piles]

My mobo has a silenced 260hp VP with the exhaust exit underwater, the most noise is in the saloon as the engine is under the floor. Even with a load of sound proofing.
On the Fal the two loudest boats can be heard in Devon. One a 1980s flybridge and the other a Seaward/Nelson which must has straight through exhausts. Neither owner cn have either a conscience or hearing.

 

[Elessar]

If no disrespect intended then call them motorboats
yes it’s different exhaust systems mainly

Mobo is not a term of disrespect!!

 

[Sticky Fingers]

Mobo is not a term of disrespect!!

Stinkpot is though.

 

[Elessar]

A couple of lads had a cheap inflatible and a chinese strimmer type outboard. It was very noisy and maybe 1hp? Could be hard miles away.

Yes. Air cooled. Basically a garden strimmer some joker has put a prop on and sold as an outboard. Don’t worry it will expire soon.

 

[Elessar]

Stinkpot is though.

I don’t mind it. As long as the person saying it would drink a beer with me whilst talking rubbish about boats.

 

[Sticky Fingers]

Fair enough!

 

[Portofino]

Older designs haven’t got underwater exhaust.Some newer have 1/2 hearted holes 1/2 submerged at the stern quarters.

The design is very important .My boat maker Mario Amati was the first with true underwater exhausts .Done properly means all I hear is water + air rushing by . Talking 12.8 L pair of diesels .

 

[William_H]

A question. Does a turbo charger on a diesel inherently reduce exhaust noise? I imagine it would but may be wrong. ol'will

 

[derod]

As far as I am aware, a turbo doesn't really impact the volume of noise, it's the fact that it is usually connected to an effective exhaust/silencer system that makes the difference. Diesels and 4 stroke petrol engines have mechanical valves to control the suck/blow part of the engine cycle whereas 2 strokes rely on exhaust back pressure. What a lot of folk don't seem to realise is that an effective exhaust and silencer will actually improve engine performance, and in the case of 2 strokes particularly, extend engine life!!
(Having said all of that, as a "young buck" I did have race cans on my bikes!!) DOH!!

 

[fredrussell]

If no disrespect intended then call them motorboats…

Just a gentle ribbing, stinkpots ‘n’ raggies innit?