Princess 330 muffler/silencer

[ROSK]

Hi
I'm the lucky owner of a Princess 330 from 1991 retrofitted with two Yanmar 6LPA engines(2011). The exhaust runs directly to the thru-hulls in the waterline aft. At cruising speed the exhaust generates way to much noise. Is there someone that has found a muffler that will fit in the aft compartment. There is only about 45 cm from the engine room bulkhead to the GRP exhaust pipe, where the exhaust hose is currently secured.

 

[QBhoy]

Lucky man. Your boat model is and has been in my top 5 favourite boats since the early 90’s. So rare these days too. That and the smaller 315, are just lovely things. Most of them made (weren’t many in the first place), seem to have found themselves abroad, as far as I can see. Lovely.
obviously a personal preference…but the old school exhausts are one of the nice things about them, I think. Just wouldn’t Be allowed these days. We have a similar era 385 with the likes, with the big 61’s.
That said…it can occasionally make you assume that not everyone might be a fan of it, in the marina. Especially owners of boats with masts and canvas perhaps.
Can’t think right now, but do you not have the exhaust flap shutters on yours ? Can help a little at idle and slower speeds in the marina. And certainly ours can be significantly quieter with a full water tank and plenty of fuel onboard. The exhausts are almost submerged in that trim.
As for cruising speed…I can’t say that the 385 is noticeably noisy from within the boat at least. No doubt she is externally to others perhaps.
what can also help is avoiding the engines being in the realms of just being out of sync with one another at cruise speed. Just to avoid the droning that can occur in that case.
Anyway. Should you wish to…I’m sure you can retrofit a water box of some sort on the way out somewhere. Be a shame to, I think though.
best of luck either way and enjoy that lovely boat.

 

[ROSK]

I've always loved "classic" lines on boats from 80's and 90's. When this boat where available earlier this year I had to buy it For the record, I live in Bergen, Norway and the boat is originally imported from Spain.
Taking it 350 nm to Bergen in some big waves passing the South-West part of Norway, the boat was handling perfectly. Soft and predictable movement, and no annoying noises from the interior.
I like the sound from the exhaust on lower revs, but we must close the doors at cruising speed. I am planning to install something... in the spring, and expecting(hoping) the sound from the Yanmars will still be nice. As for a little more details, diameter of exhaust hose is 100mm - 4'', Yanmar 6LPA - 295 HP. Found some nice pictures of the exhaust pipe, and the boat...

 

[oldgit]

A longish tale.
Exactly the same problem with the Princess 35.
Once had a Broom 37 with a similar non silenced set up.
It boasted a air of M135 Perkins with straight through exhausts , sounded like a million dollars on start up and while chugging along at 5-6 knots. No problem on inland navigations and other non tidal waters.
However after about an hour at any sort of wider throttle openings the attraction started to wane, the constant drone was a right pain, after a 6 hour trip it was mercy to arrive and turn off the engines.
The final straw was when helping to move a little 30 ft Hardy owned by an aquaintance . On engine start up you could not hear anything other than a soft burble from the stern , little more even when getting move on. ie 10 knots

Decided to investigate some sort of noise reduction for the Broom and after consulting this forum , advice from " Latestarter" discovered the eyewatering costs of pucker " Halyard" devices.
A tape measure and a look in the Broom lazerette suggested there was just enough room to insert a very basic waterlock device in the middle of the long exhaust pipe.
Purchased a couple of budget waterlocks fron a Dutch company (Pre-Br*** ) , 5 mins spent with an angle grinder and then half a day cleaning up the carbon dust, finally got the waterlocks installed.
The difference was instantly obvious, not silence, but you were able to actually hear the water slooshing around the stern of the boat on the flybridge, while underway.
The Broom eventually outstayed its welcome and was replaced by a Princess 35. Faster and with much better seakeeping.
On the very first proper trip out the unholy row coming from the exhausts instantly reminded of just how noisy the Broom used to be and what some simple silencers could achieve.
Alas the layout of the the exhaust system on the P35 + serious lack of space in lazerette , precluded the addition of any extra silencers, suspect the P330 is even worse.
OGs latest money pit, features a pair of Yanmars, with not only proper silencers in the exhaust but the exhaust exits under water, you can now hear people complaining about wash as we go past.
We have a couple of P330 plus a couple of P35 on our moorings, good solid practical boats.
We also have 2 x 415 and pair of P45 all of that era.
All of them have stood the the test of time well.
Nearly forgot a P 410.

 

[Dino]

Two friends of mine had older VP powered Princesses, a P35 and another had a P415. They were both straight through exhausts and you could hear them coming from miles away. They were both lovely boats but you could really hear them coming.

 

[Portofino]

If you are DIY handy and the boats on the hard ( in a yard with glass fabrication guys ?) anyhow try underwater exhausts .UE are the best way to silence the noise .
Actually was invented / first leisure boat application by Amati ( Itama spelt backwards) way back while Princess and others where doing what you have now . A lot have since copied this aspect .

It looks simple enough for you to do in that space shown on your pics .
Here are a few pics for ideas .

Its a box inside with the main exhaust entering from the top .The WL is approx where the top of the racor is .The little pipes are from the g box and oil coolers Behind obscured partly is a “ fart pipe “ to the transom .This is to allow low pressure eg tick over in the dock fumes + water to exit at the transom……ok a bit of noise , but hardly noticeable below 1000 rpm .



Port side showing the main cooler elbow entrance on the RHS , above the rubber .
Again smaller oil coolers water outlets go direct into the box - LHS .


Box pics from the engineer ( replacement exhaust in SS done during covid lockdown) , you can see the fart pipes configuration , it gets a bit of water feed from that branch from the g box oil cooler ….so I see a telltale water flow at the stern .Obviously there’s a lot of latitude in the final design .You can configure the pipage to suit your situation.


Sorry pic on its side showing the orifice under the hull .It’s sort of stream lined going aft, with a deflecting flap .
There’s a suggestion the gasses in this example run back over that outer 1/3 rd of the hull and reduce friction , break up the wetted area ….I will leave it at that as on previous threads folks claim it boring talking about hull form .
Chicken + egg scenario ? Did he invent this to increase performance efficiency of his boats back in the day ( 1980s ) or reduce noise ??

But it certainly reduces noise which is what you are enquiring about.


You can see the flap ^^ here so @ speed and with turbos spooling full chat @ 30 knot cruise the gases are sucked out , ie zero back pressure.


The “ fart pipe “ for low speed / marina manoeuvres + to eye ball water = always reassuring btw .
Again you can configure this to suit , but you already have a hole any how so use that .
A certain amount of back pressure is desirable with diesel exhaust.

 

[ROSK]

Up until now there are two solutions I'm favouring.
1. Leading the exhaust under water, however this requires competent GRP/GRE work. One example is documented for a nice Princess Riviera 36. Riviera 36 exhaust ( and DIY projects)
2. Modify Standard water lock or design/make water lock, with criteria 25 litres and 4'' connections. Probably with a 90° bend running through the bulkhead. I've seen this done on P35.
View attachment 144356

But still, right now I'm looking for other alternatives

 

[QBhoy]

If it helps any…not cheap…but I have corsa marine diverter captains call system on my smaller boat. Can put straight through or under water.

 

[harvey38]

I quite like the sound of my non-baffled Sabres, maybe it's the flaps that help keep the noise down.

 

[Portofino]

When you bin the exhaust noise ( via under water exhausts ) it leaves others .
For me turbo whistle of MAN s KKK spooling up is music to my ears .Others will disagree as sound like pop music is subjective

The pic a bit crappy but the sound is good ( imho ).

11 knots pootle to 26 knots in a measured less than 10 secs on its way to cruise 30 knots a few sec s later .

The whistle ….Oh my .

Granted a pair of DD s whistling way in a marina manoeuvres sit at the pinnacle of mobo engine noise …..but this is enough for me . DD s boats tend NOT to have under water exhausts , so whilst they take the crown in the marina they ate tire some @ cruise in use .

 

[oldgit]

One quick point, Latestarter did go on at some length that exhaust back pressure must be considered when adding anything DIY to the exhaust path,it could cause problems.
Not so vital on a couple of asthmatic normally aspirated stone age Perkins but it could be expensively terminal on a high performance engine.

 

[sap_2000]

Congrats with the new boat
I think we talked on phone regarding delivery to Bergen before you decided to do it yourself.

Having spent many years on a P35, it had retrofitted tube mufflers. It helped quite a bit on the noise at cruising speed and at idle. They were fitted in the lazarette just before where the GRP exhaust tube connected to the original hose. It was a matter of just cut away the exhaust tube and fit in place.

These are from VP but many make similar. Look in Maritim.no

The one in pic is small, but they make them bigger also

 

[ROSK]

Yes Sap it was maybe not my best decision, but I got home in time for our vacation.
As for the plan now I have ordered a waterlift/ tube muffler from Watski. I was going to take a lot of measures, but as they had a good offer and a assume it is the cheapest and easiest solution. Will probably order the second one next week. Later I will try to find or make a solution for leading the exhaust into the water.
I uploaded a video to youtube that shows the issue with water splashing onto the wood decking. You can also hear the exhaust noice level at idle….

 

[ROSK]

Hi
I received the muffler yesterday. Wanted to see the inside, and tried to push the two ends together as much as currently possible. Managed of cause to over torque the hose clamp ? Typical...
The muffler looks nice though. They could maybe spend two minutes more in the assembly line, as it was not properly aligned, and I got a spare bracket..
The price was acceptable at about 420 pounds.