Are Yanmars loud by their nature?

[Blissboat]

Over the past year I have ridden along or sea trialed a few boats in the 30' - 40' range with single, in-line six cylinder diesels of various manufactures - Cummins, CAT, Perkins, Deere and Yanmar. The latter has become really common in the range of boats I am looking at, especially the 6LYA-UTE (315 hp).

Twice now I have been turned off from a boat with that Yanmar because, when underway at cruising RPMs, the engine noise inside the cabin is uncomfortably loud - enough so that it's necessary to lean in close and almost shout to be understood. Having a casual conversation is impossible. I love diesels as much as anyone, and the happy clatter of a compression valve train rumbling steadily, hour after hour, has always told me all's well in the engine compartment. But the level of noise I've been experiencing with Yanmars in this displacement bracket gets old really fast. I think a five or six hour day trip would be downright unpleasant, for me and for my passengers.

One of the boats I tested was a 30' Mainship Pilot II, with the 315 hp Yan. To be fair, the Mainships have a reputation for being loud. But some Mainship owners report having invested in upgraded sound suppression (e g., SoundDown), and found there was little improvement. That suggests the boat itself may not be the problem, and that it's the engine. Now more recently I sea-trialed a 32' Downeast style semi-custom boat with the exact same 315 hp Yanmar, and found the noise level in the cabin was again uncomfortable. It was loud enough so as to take away the pleasure of being underway. My surveyor agreed, and commented that the builder had gone to a lot of extra trouble to contain noise in the engine compartment, and the insulation beneath the access hatches appeared to be as good as SoundDown - two thick layers of dense, foil-backed foam with an inner layer of lead foil.

Everyone swears by these Yanmars, saying they're the next thing to bulletproof. But now I'm becoming gun shy about traveling to look at any more boats so equipped. The best experience I have had in this regard was with a 42' Downeast powered by a single Cummins 6CTA 8.3, at 400 hp. It sounded sweet at any RPMs. That was a bigger engine in a bigger boat, of course, but does that explain everything?

 

[Iggy]

I have have the same engine and love it. I can't say that its overly noisy and my helm is right over the engine. No yelling or raised voices on my boat.

I would look for a manifold leak or a muffler problem.

 

[jrd22]

Two of the water taxis in our area had those 315's and they were obnoxiously loud but they changed out one boat to Cummins and it was just as loud. Might be an rpm difference at cruise, I think those Yanmars are a 3500 rpm engine (not sure about that model) and the others you listed might be lower depending on model.

 

[Bacchus]

My opinion is noise level is more a function of boat design than engine. There are likely some engine to engine differences but my 08 MS 34 HT is very quiet with Yanmar 370 6LYA even at high cruise - 2800 RPM & 12-13 MPH. There are no hatches in the saloon and engine Rm access is from the aft deck. ER i
ER Has sound insulation on entire ceiling area.

 

[Lepke]

Diesels make noise by ignition, exhaust, and transmitting sound thru the boat's structure. Yachts usually have some sort of shock absorbing motor mounts. There may be better ones available. Noise also comes from the exhaust. Wrapping all exhaust and turbo with sound sound deadening material helps a lot. Proper sound proofing can make a huge difference. What seems to work best is lead sheeting and foam. You could put lead sheets below the carpeting or foam, the thicker the better. You can't put foam in the engineroom because in a fire foam gives off toxic gas. There are cheaper forms of sound proofing than lead, but it works best.
If you are overhauling an engine, using Speed of Air pistons will dramatically lower the noise. These are the pistons with dimples in the top and a ceramic coating on top. They also lower EGTs by about 200° in turbo engines, greatly extending life. Most people I know are reporting about a 20% increase in mileage. Speed of Air pistons are also bringing hwy diesel engines within smog compliance with smog devices and DEF removed.
My engine room has professional sound proofing done 50 years ago and still working. I have twin Detroits and directly over the engineroom can have a normal conversation. And the engines are directly bolted to the hull structure,so I am getting some sound from that path.
Some people build a box like a generator uses, over their engine. But you have to ensure enough unrestricted air flow and have an idle cooling period after running so the high temps don't damage accessories.

 

[ranger58sb]

Twice now I have been turned off from a boat with that Yanmar because, when underway at cruising RPMs, the engine noise inside the cabin is uncomfortably loud - enough so that it's necessary to lean in close and almost shout to be understood. Having a casual conversation is impossible. I love diesels as much as anyone, and the happy clatter of a compression valve train rumbling steadily, hour after hour, has always told me all's well in the engine compartment. But the level of noise I've been experiencing with Yanmars in this displacement bracket gets old really fast. I think a five or six hour day trip would be downright unpleasant, for me and for my passengers.

One of the boats I tested was a 30' Mainship Pilot II, with the 315 hp Yan. To be fair, the Mainships have a reputation for being loud.

Don't the Yanmars rev significantly higher than other diesels of similar displacement?

If so, is that a factor?

-Chris

 

[Iggy]

Don't the Yanmars rev significantly higher than other diesels of similar displacement?

If so, is that a factor?

-Chris

I have the same engine that the Op is talking about. At 1800 to 2000RPMs. My boat does between 7 to 8 knots on a 40 footer that is about 28,000lbs. Max for that engine is about 3300RPMs.

I think this all goes back, not to repeat it. What has already been posted. I don't find mine noisy at all.

 

[ranger58sb]

For comparison... our max RPM is 2300, and we run ~8.5 kts at ~900 RPM or sometime less... and we're roughly 55' and 58K lbs, something like that... and we only have a flybridge helm... so at trawler speed, we don't hear our engines much.

-Chris

 

[Iggy]

For comparison... our max RPM is 2300, and we run ~8.5 kts at ~900 RPM or sometime less... and we're roughly 55' and 58K lbs, something like that... and we only have a flybridge helm... so at trawler speed, we don't hear our engines much.

-Chris

Do you have twin engines?

 

[Keysdisease]

My opinion is noise level is more a function of boat design than engine.

This is very much the truth. There are noise differences between brands on similar HP in-line 6 cylinder engines, but not enough to influence noise differences in the cabin or cockpit. In other words, the differences might be measurable, but not noticable.
As mentioned noise on a vessel will be the sum on several sources. Start at a baseline of upper 70 to 80Dba for just wind and water noise at 15 to 20 knots. Add to that:
Mechanical noise from the engine
Intake stroke noise from a any natural aspirated diesel
Structure borne noise through the engine mounts
Structure borne noise from the propeller (prop rate)
Exhaust noise including structure borne noise from hose/pipe/mufflers
These are the most prominent sources of engine noise on a boat.

In the Mainship example you gave the well known sources are the prop tip clearance in the tunnel(s) and the scheme to bring combustion air to the engine space through inside the cockpit. Another common source of noise on many vessels are uninsulated voids between the hull and inner-liner open to the engine space. This is exaggerated when stereo speakers are installed in this inner liner. These type noise "leaks" can add up to significant noise.

There are noise reduction treatments for all these sources, and the sum of addressing them will result in a "quiet" boat, which typically means being able to have a conversation with someone next to you in the cabin without shouting.

A sensible way to address these noise sources is by "bang for the buc" and ease of installation. For example gaskets on all engine room hatches can result in a 5Dba + reduction for little cost and very easy installation.

There are many misconceptions about insulation products. First and most common is foam/fiberglass/"soft" insulation are noise absorbers, but not noise barriers. Mass is a noise barrier, and lead was replaced last century with Mass Loaded Vinyl (MLV) in the same weights as lead, usually 1 or 2 lbs per sq ft. The performance of mass is improved by decoupling it from the structure with foam or fiberglass.

Noise really does not care what the mass layer is made of, 2 sq ft of lead/MLV/ concrete/whatever will all work the same in the "noticeable" spectrum.

A common misconception about engine room insulation is "the ER hatch is insulated." The overhead of most engine spaces are framed with the same or similar materials as the hatch. Insulate the hatch and noise just goes thorough the uninsulated sections of the overhead. If you choose to insulate the ER overhead, to be truly effective the entire overhead needs insulation to where the cabin sides are, beyond that is a weather deck that really doesn't need insulation. And neither does hull sides, at least not barrier products. Absorption insulation will help reduce engine noise in the ER, which will add marginal performance to an insulation "package"

One of the most overlooked problem areas is engine space air trunks. Any air trunk that is above the ER overhead can be a major source of noise. On many vessels these vents can be seen on the sides of the cabin, and are just extensions of the engine room invited into the walls of your salon.

Just my $00.02

 

[Bacchus]

A sensible way to address these noise sources is by "bang for the buc" and ease of installation. For example gaskets on all engine room hatches can result in a 5Dba + reduction for little cost and very easy installation.

In addition to hi mass barriers the point of sealing very small gaps is critical for noise control. A good example is perhaps a solid core door, even one designed for noise control, can only be effective if it includes a COMPLETE seal designed for noise control. A small gap in an effective seal may seem insignificant compared to all the other well designed features but can "leak" sound waves. The amount of "noise" that leaks thru a gap is not proportional to the size of the gap vs the are " well protected".

IMO the design feature that sets our MS 34HT apart from many boats is the absence of any hatches in the ER / living space. By moving the ER access to the aft deck MS has moved the openning & difficult to seal pentration out of the living space.

I have taken noise readings, while underway in different conditions, and without exception the fully closed condition - all doors, windows, hatches, closed, is quieter. I dont believe that is the case with all boats, especially the ones where owners complain about noise underway.

 

[Blissboat]

This is very much the truth. There are noise differences between brands on similar HP in-line 6 cylinder engines, but not enough to influence noise differences in the cabin or cockpit. In other words, the differences might be measurable, but not noticable.
As mentioned noise on a vessel will be the sum on several sources. Start at a baseline of upper 70 to 80Dba for just wind and water noise at 15 to 20 knots. Add to that:
Mechanical noise from the engine
Intake stroke noise from a any natural aspirated diesel
Structure borne noise through the engine mounts
Structure borne noise from the propeller (prop rate)
Exhaust noise including structure borne noise from hose/pipe/mufflers
These are the most prominent sources of engine noise on a boat.

In the Mainship example you gave the well known sources are the prop tip clearance in the tunnel(s) and the scheme to bring combustion air to the engine space through inside the cockpit. Another common source of noise on many vessels are uninsulated voids between the hull and inner-liner open to the engine space. This is exaggerated when stereo speakers are installed in this inner liner. These type noise "leaks" can add up to significant noise.

There are noise reduction treatments for all these sources, and the sum of addressing them will result in a "quiet" boat, which typically means being able to have a conversation with someone next to you in the cabin without shouting.

A sensible way to address these noise sources is by "bang for the buc" and ease of installation. For example gaskets on all engine room hatches can result in a 5Dba + reduction for little cost and very easy installation.

There are many misconceptions about insulation products. First and most common is foam/fiberglass/"soft" insulation are noise absorbers, but not noise barriers. Mass is a noise barrier, and lead was replaced last century with Mass Loaded Vinyl (MLV) in the same weights as lead, usually 1 or 2 lbs per sq ft. The performance of mass is improved by decoupling it from the structure with foam or fiberglass.

Noise really does not care what the mass layer is made of, 2 sq ft of lead/MLV/ concrete/whatever will all work the same in the "noticeable" spectrum.

A common misconception about engine room insulation is "the ER hatch is insulated." The overhead of most engine spaces are framed with the same or similar materials as the hatch. Insulate the hatch and noise just goes thorough the uninsulated sections of the overhead. If you choose to insulate the ER overhead, to be truly effective the entire overhead needs insulation to where the cabin sides are, beyond that is a weather deck that really doesn't need insulation. And neither does hull sides, at least not barrier products. Absorption insulation will help reduce engine noise in the ER, which will add marginal performance to an insulation "package"

One of the most overlooked problem areas is engine space air trunks. Any air trunk that is above the ER overhead can be a major source of noise. On many vessels these vents can be seen on the sides of the cabin, and are just extensions of the engine room invited into the walls of your salon.

Just my $00.02

Keysdisease, all your observations make sense, and three in particular stood out in the context of the boats I have been evaluating. The part about insulating all the ER overhead, all the way out to the hull sides is clearly true, but hard to inspect for, much less remedy, when the builder has shoehorned so much into the compartment that you have to lie face-down on the cabin sole just to reach anything.

Your explanation of MLV (mass-loaded vinyl) struck a note. A boat that I recently tried to buy had been equipped, obviously by the builder, with heavy, black, stiff rubber-looking curtains attached by screws to the under-deck stringers, hanging down to a point just above the hull stringers. These curtains were placed about a foot or so away from the either side of the main engine, roughly matching the outline of the engine compartment hatch. They didn't form a tight seal, but I interpreted them as being there to reduce the acoustical volume of the engine compartment, shortening the distance for echo to travel and containing some of the engine's sound reverberation. Would that have been MLV, do you suppose? The material may be good, but the way it was deployed seemed ineffective.

And then about the air trunks - brilliant. I hadn't even thought of that, but as soon as I read your words the lights came on. That boat I recently took to survey and sea trial, then declined, had air intakes on both of the cabin sides, with the grid covers about sixteen inches above deck level. Given the narrowness of the cabin and its walls, it seems very likely that's where a lot of the engine noise at cruising RPMs was radiating to the cabin's interior - in stereo, no less!

I had such a mad crush on that boat, it was disheartening to realize that being underway was kind of miserable, so I kept thinking how I could fix it. Attacking and resolving those things in a 32' downeast style cruiser would be possible, but given the crowded space, I could see having to remove the built-in salon furniture, take up the decking and possibly even detach the engine and genset from their mounts in order to work everywhere. Nope. I need a boat that's ready to be enjoyed, not a ready-made boat project.

 

[ranger58sb]

Do you have twin engines?

Hmmm.. yes, hadn't thought to take that into account for comparison.

OTOH, it'd maybe be comparing running at higher RPM on a single engine setup, or the sound of two engines. Don't know which I'd expect to by quieter/louder.

-Chris

 

[Keysdisease]

Would that have been MLV, do you suppose? The material may be good, but the way it was deployed seemed ineffective.

Yes, most probably was. And yes, on these (sorry) smaller boats the ER overhead can be challenging to insulate.
For those that have no issues with carpeting, there is an acoustic carpet underlayment that works very well, and does essentially the same thing as engine space insulation but on the salon floor instead of the ER overhead. In the case of a Mainship Pilot this treatment on the "bridge deck" forward of the cockpit is very effective.

Carpet Underlayment - Soundown Products

soundown.com

 

[Keysdisease]

I had such a mad crush on that boat, it was disheartening to realize that being underway was kind of miserable, so I kept thinking how I could fix it. Attacking and resolving those things in a 32' downeast style cruiser would be possible, but given the crowded space, I could see having to remove the built-in salon furniture, take up the decking and possibly even detach the engine and genset from their mounts in order to work everywhere. Nope. I need a boat that's ready to be enjoyed, not a ready-made boat project.

These air trunk issues can often be treated by removing the vent cover on the outside and lining the inside of the air trunk with 2lb MLV (1/4" thick) There is often enough room to reach inside the trunk and glue the MLV to the 3 sides (and top) of the trunk with some epoxy glue all the way down to deck level. No need to treat the outboard side.
Also:
The part about insulating all the ER overhead, all the way out to the hull sides is clearly true,
I said "to where the cabin side are." Beyond that you are insulaating the underside of the outboard side decks which do not need to be insulated, just like hull sides, that noise is radiating off the boat, not into the boat.

o7

 

[Keysdisease]

But some Mainship owners report having invested in upgraded sound suppression (e g., SoundDown), and found there was little improvement.

I suggest this is more an application/installation issue than a boat/engine product issue. As I described previously, if you upgrade the insulation on your engine room hatch, you will not get much noise reduction. The noise will just radiate around the hatch and come through the deck without the upgrade.

As I mentioned previously, a methodical approach, addressing the least expensive and easiest to install treatments first, and then working your way down the list through the other treatments until you find a happy place to stop is a reasonable way to address noise reduction on these type boats.

$00.02

 

[Pathfinder]

You should try riding on a Mainship 400 like ours (Pathfinder). We usually operate from the fly bridge and not much noise at all.

 

[Vicki Z]

It's the boat, not the motor. My pilot 30 315 Yanmar noise improved with a different prop. It's is so much quieter than a Blackfin with twin volvo diesels. You seriously need ear protection on that thing. Step onto a 38 True North with a 440 or 480 Yanmar depending on the year, and it is quieter than any modern outboard powered boat I have been on. The amount of effort that was put into quieting down the engine, exhaust and driveline noise is impressive. I understand why manufacturers go the outboard route. All the noise is already behind you. Step onto a 42 Legacy with a Cummins QSM11 and again, ear protection might be in order.

Steve

 

[rgano]

I feel like I might have some cogent input since my Yanmar 6LPA-STP equipped Mainship 30 Pilot II is one of the boats Blissboat rode. I have the hardtop model (sedan), and that HT probably has some impact on the noise at the helm, directly over the engine. I have Bomar hatches over the two pilot seats and just for fun can stand on the helm-side seat with my upper torso through the Bomar using a bare foot to turn the helm. That's the same acoustic effect as if the boat was flying bridge equipped when I am running the boat at 3000 RPM - lots of difference and not wildly different than when I left my Grand Bank's lower helm and went to the flying bridge with both NA 120 HP engines rumbling along at 1800 RPM. Another factor not mentioned above is the side exhaust on the helm (stbd) side of this model boat. Then there is the open aft end of the "bridge deck" as Mainship calls the top of the engine hatch. If I lower the aft isinglass/canvas enclosure, I get a significant noise reduction. Mention was made of running the engine at 1800-2000 RPM which is VERY much less noisy, but neither the engine nor I like that speed. I bought this pilot with this power to enable me to roughly double my previous putting around speed in my twin FL 120 GB42, and I'm darned if I am going to plug along at hull speed when I don't have to. Although I seldom use them unless on an hours-long run, I have a two sets of earmuff intercoms which reduce the need to speak loudly and reduce the noise stress to nothing. I don't mind sticking in a set of earplugs from time to time on shorter runs. I have employed most if not all of the noise reduction tactics mentioned above, and owners of an unaltered sistership tell me the noise at the helm is significantly less than their boat, but there is simply no getting away from the fact that sitting with your ears six feet away from a screaming turbo charged, side exhausted Yanmar 315 HP engine is going to be a quiet day at the park.

 

[OldDan1943]

Take a ride an American Tug. Not much noise. Any noise you get used to. Sort of like your car, dive by sound.
I have a sound shield on my NL gen, so quiet, I have forgotten it is running