mystery noise help needed

[portlandtug25]

Hello Factory Folks,

While it has been a good boat with few issues( I bought it new) a problem seems to have developed with my 2015 R 25 (Volvo D3, 450 hours) that is becoming very frustrating.

At any RPM between approximately 1300 and1700, there is a high pitched resonation that fills the cabin. The sound is not like a gear whine that changes pitch with RPM, but rather a continuous high pitch sound that is somewhere between a whistle and a ringing, ( maybe two octaves above middle C, for the musically inclined). It first appears at 1300 RPM, stays at the same pitch until 1700, at which point it fades away. The sound wavers a bit in volume through this RPM range and at times seems variable depending on current direction and/ or rudder angle, though this effect is very slight, and inconsistent. ( I'm on the Columbia River). Again the pitch does not change between those two engine speeds, only slight variation in the volume of the noise.

The upshot is that I can run at 1290 (One gal./hour) with very quiet operation or above 1700 (2 gals./hour) with normal noise level, but anything in between is very unpleasant. The effect seems to be worsening with time. When I first got the boat I found 1300 to 1600 RPM to be a useful range, in terms of speed, fuel consumption and noise level--low noise level being one of the things I appreciate about the RT.

I have maintained the boat to factory specs (as per owners manual) since new utilizing the local Volvo dealership.The boat runs and handles perfectly otherwise.

I would appreciate any help you can offer.

Thanks,
Roger Friedel


.

 

[bob daily]

Mr Roger, some previous post on this subject ( Prop Sing ) you might want to check out. Also information on the web. Bob

 

[trailertrawlerkismet]

First thing that comes to mind for me is the drive shaft not getting enough water. Please keep us posted as to the fix so we can all learn. Have you tried putting the transmission in neutral and rev the engine up to the rpm where you hear the noise? If you do or have and you hear no noise then it could be drive shaft related. If you do and hear the noise then I’d say it is not the problem but it at least puts you thru a process of elimination. What about turbo related?

Jim F

 

[portlandtug25]

Thanks,
Articles on WWW say it's not uncommon. To mitigate you have to file the facing edges of prop blades. (not something I 'd want to try myself, so maybe have to talk to a prop shop). Articles say it's not harmful, just annoying. I can't find earlier postings on TugNuts about this.

Probably not turbo. No noise at any RPM when in neutral. Had a drippy stuffing box tightened a while back by experienced Volvo mechanic, but noise predates that. Maybe made it worse? I don't know. Would appreciate any other ideas/comments.

Thanks,Tugnuts

 

[bob daily]

Mr. Rodger, The easiest way to rule-out prop sing would be to change or swap out the prop! Maybe someone in your area has a spare prop you could borrow or would be willing to swap for a short time.
Hope you find the problem and please let us know the outcome. Bob

 

[BB marine]

Your noise could be from a number of issues. The easiest way to find the source is open the engine hatch while cruising and at least find the area of the noise.

If you find it is coming from the engine area I would suspect it is the turbo. What is the condition of the air cleaner? The air cleaners used have a tendency to deteriorate and fall apart. Having an opening in the material will allow more turbo noice to be present. The variable geometry turbo will start to boost slightly above 1200 rpm The ECM controls the boost by moving the vanes. This is unlike a standard turbo that needs higher rpm increase to create more exhaust flow to spin up the turbo and have a waste gate to control max boost. The turbo at lower RPM will tend to whistle. A engine will load differently as the boat is loaded with more stuff. This can change the way the VGT turbo boost. Things to look for. Using the Volvo EVC look at the boost numbers through out the rpm ranges What boost # is the EVC showing at the RPM range that you are experiencing the issue? Then bump the throttle up and look at the RPM that the noise goes away and check the boost numbers. What is the Max RPM that the engine will turn? It should be 3100 rpm and no less than 3000 rpm. What is your boost at this rpm? Should be around 20PSI. If you have loaded the boat to reduce WOT rpm the boost will change at different rpms . Remember the ECM controls the boost in a VGT turbo. The ECM will not boost the same when in Neutral and neutral WOT is limited to 1500 rpm D3 Volvo.

Shaft noise? While running at the rpm that the noise is present. You should be able to hear the noise coming from the gland. When running at 1300 to 1700 CAREFULLY put your hand on the gland, if it feels warm and you feel the vibration that matches the sound patterns this may be were your issues is. This gland gets lubricated from the water flow coming from the raw water return to the exhaust riser. There is a 3/8 hose that feeds water to the packing lubricating it and the Cutlass bearing. If this water flow is restricted there may be a dry run causing it to squeal. Increasing the rpm may increase the water flow because the raw water pump is increasing flow as engine rpm picked up.

Check the front section of the engine alternator belt, Raw water pump belt, belt tensioners, Alternator bearing noise, Look for rust bleeds on the front of the engine. If you notice it is louder in this area. It may be caused from one of theses items.

Open the back seat area up. This will put you in the area of the prop tunnel. If the noise seems to be amplified in this area you will know to address a possible in balance with the prop. Again run @ WOT check rpm full rpm ? increased vibration?

You must find the area that the noise is coming from first. Next determined what is causing it. Use the old fashion noise detector. 3/8 4' long oak dowel rod place the rod on an item in question the other end up to your ear. Listen to the vibrations . This will help you zero in on the source then you can troubleshoot the cause.

Good luck in finding the source of the whistle!

 

[GaylesFaerie]

3/8 4' long oak dowel rod place the rod on an item in question the other end up to your ear. Listen to the vibrations .

Wow that reminds me of an old Car Talk episode where the boys recommended using some vinyl tubing in the same manner to find valve ticks. Simple, elegant and effective. Gosh I miss those broadcasts.

 

[portlandtug25]

Thanks Brian,

I'll check all those items you list, before I haul the boat and swap or work on the propellor.
Not sure I understand the turbo boost part:
What boost level should I see at just above 1200 or anything less than WOT? I would expect it to be less than WOT ( 20 psi) Also not sure what a waste gate is!

The puzzling thing to me is that the pitch is so constant. If it were the turbo, or the shaft or even a belt, I would kind of expect there to be some change in pitch as RPMs increase---but maybe not! The constant pitch is is what all the "prop singing" articles talk about, so I was going by that.

This engine runs at about 2950 WOT, with 2 people, a dog and full fuel and full fresh water, but I will check that again too since I almost never run WOT.

I appreciate very much your thorough analysis of this situation!

Thanks again.

 

[KARL]

We experienced the same thing on our 2015 RT27. It's the silicone hose coming out of the top of the turbo. The hose clamp slipped partially unsealing it and we got the noise starting at about 1300 'RPM and up. Simple fix of making sure the hose is on properly and re-tightening the clamp.

 

[portlandtug25]

Thanks! I hope it's the same situation with mine. I'll check it out .

 

[BB marine]

I beleive what Carl is speaking of is the silicone hose from the bottom discharge of the Turbo to the top of the After cooler.Volvo uses inexpensive hose clamps in this application. The Hose clamps loosen and the hose begins to leak turbo boost. If the seal is still relatively good but just leaking from a location where the clamp is causing a pinch it will whistle. If this hose is leaking there. You may see evidence of oil too. This is carry over oil from the crankcase ventilation filter and also from the plain bearing seal in the turbo. Both are normal, the engine scavenges it during combustion. I had this issue on my C26 220hp at 450 hours. The issue I had was the hose deteriorated from the elevated air temperatures ( 350 hours of use before installing the complete compartment ventilation ) carrier over oil and the hose clamp continually loosening up. I found it loose and tightened it 3 times before complete failure. This eventually caused the silicone hose to fail. Volvo supplied a new turbo and hose. The turbo was not bad based on the specs that I received from Garrett Turbo but Volvo said to change it. The job required removing the after cooler and Turbo. When I reassembled I installed a wave washer spring hose clamps to insure positive clamping. (This type of clamp is used for this application and was recommended by Garrett Turbo.

If this is your issue you would find it when inspecting the air cleaner and turbo for noise. You will also find the area around the hose to be oily.

I am posting some pictures of what could be a simple tighten the clamps. But I would advise replacing the clamps with a better quality clamp before you end up have the issue that I had.

gallery2.php?g2_itemId=69838
gallery2.php?g2_itemId=69984&g2_imageViewsIndex=1

Turbo and Afttercooler removed to install new hose
gallery2.php?g2_itemId=70013&g2_imageViewsIndex=1

New style Turbo clamps installed
gallery2.php?g2_itemId=70540&g2_imageViewsIndex=1
gallery2.php?g2_itemId=70537&g2_imageViewsIndex=1

This may or may not be your issue but it was a good suggestion from KARL. If you find that the noise is coming from the Turbo area and you find that the hose clamps loosening it could be the cause. If it is or not I would still advise going one step further and replace the clamps with a better quality clamp. I have had several Tug and Cut owners message my about this issue with their D3 Volvo. Most are at the 300 to 400 hour range. I believe some contributing factors are elevated compartment temperatures and poor quality hose clamps.

Another common factor for folks having this issue.
If you load your boat onto the trailer, use engine power to drive on the trailer and have the D3. Theses boats do not slide on the trailers well. When driving on the trailer and using the engine. The Turbo will go into a high boost quickly because of the VGT. (Variable Geometry Turbo) The engine rpm does not climb as it normally would because it is highly loaded trying to push the boat onto the trailer. This increases the boost pressure and can cause the hose to expand and start to leak if the clamp is not applying proper clamping force. Just my opinion!

 

[portlandtug25]

Thanks Brian,

I assume that the silicone hose and( possibly faulty ) clamps will be obvious once I get that quilted aluminum-looking heat shield off.

I appreciate your time on this.

 

[portlandtug25]

For those sleuths who are following this thread, thanks, and here's an update:

I spent an afternoon on the river using a 3' stiff plastic tube "stethoscope" , and with the help of a friend manning the helm, I found the following:

1.No unusual noise from front of engine: belts, alternator, raw water pump, etc at at any RPM under load.
2. Using same tool around the turbo area, no unusual noise at any RPM. Boost pressure was 20+ psi at WOT . (the Garmin gauge doesn't give an exact number--there's only a mark at 30psi) Air filter looks almost new, though by the book, it's due for replacement.
3. using the "scope" at the stuffing box, no unusual noises at any RPM. And the gland remains cool to the touch, plus I can see water dripping into the bilge, which seems to rule out packing gland problem)
4. Using the same tool listening under the removed rear seat and live well, around the area of the rudder, I found that very same noticeable high-pitched " singing" in the RPM range in question. (Only louder, apparently because the rear seat was opened up.) Additionally, when we turned the boat to port to head back to the marina, with the rudder at some angle to the prop ( there's no rudder angle indicator) there was a brief period, before the rudder returned to 0 degrees, where the noise stopped. It came back when we returned to a straight-ahead course.

Not sure exactly where this leaves me, but very possibly Bob Daily's "singing prop" suggestion is correct. Does any one know the prop specs on these R-25 Volvos? Or where to find a spare prop, in order to swap for a test?

Thanks all!

 

[BB marine]

That is actually good news. I believe the prop on the R25 is 17X15 but I don't know how much Cup. I would Email Andrew I'm sure he knows. It is strange that you never had this issue and then it came on. It was not there from the beginning. This would make me think now that you have narrowed down to the prop . ( Nice call Bob) The prop may be out of balance. All rotating equipment is designed to have what is called a critical speed. Normally engine manufactures will move the imbalance to a rpm that is not desirable to run at. Most marine engines that is somewhere in the midrange. I don't think it would be 1300 to 1700 because that actually is a desirable rpm to run at for decent fuel economy. The engine still will have some vibration and cause some harmonics. This plus a unbalanced prop may be causing the prop singing. I have heard of this but never experienced it or troubleshoot it before. I would speak with a Knowledgable prop shop or give Acme Prop a call theses guys are very helpful and knowledgeable. They probably know what prop is on your boat and can explain causes of the"Prop sing". Good luck and good troubleshooting.

 

[bob daily]

Check out the post by NORDSKI on September 5th 2021 titled (Prop Sing) on this site. His was on a R-21 model. There are a lot of prop shops in the Portland area according to the web so I'm sure you will get it fixed with little trouble! Good luck. Bob

 

[portlandtug25]

Update on mystery noise: Hauled the boat to prop shop. here in Portland. After a little a little balancing, filing (and who knows what else), the noise is gone. The boat runs as smooth and quiet as I can ever remember in 500 hours of us, from idle through WOT.

The prop was difficult to remove having never been off and the shop had to fabricate a custom puller, being that the prop has a little different hub shape than other props, but they didn't charge me for that.

So Im back to cruising in my favorite RPM range, enjoying two of the best features of the R25, namely quiet running and good fuel economy.

Thanks to all contributors.