My R-25's engine rattles/chatters at 3200-3400 RPM

[baz]

In a previous post I had mentioned that my R-25's Yanmar 150 HP engine emitted a terrible clattering sound at around 3200-3400 RPM. Shifting to just below or just above this RPM range resulted in the clattering to go away. I thought it was valve chatter and timing belt rattle. The noise was irritating and I thought maybe something was wrong with my engine. I chatted with the Yanmar person at this years Bremerton gathering to see if I could find a reason for this. After describing to him the issue and mentioning that it was a noise that was not apparent until recently we started to discuss any recent engine servicing activities that may have disturbed things etc. Well, I had the Yanmar hoses replaced per the recall and that maybe when the various engine components that had been loosened were reconnected and bolted back into place that maybe some of those bolts weren't tightened down securely. The Yanmar technician and I went to my boat and we looked at things and the obvious item that needed to be checked were the beauty metal engine covers. The technician was of the opinion that the chattering noise I was hearing could be a harmonic issues at the 3200-3400 RPM level that the noise was heard at. He suggested I check all the various bolts to ensure they had been tightened down properly.

Well, today I had the chance to do this, and guess what... I did find two bolts that were not quite seated down. I started the engine up and pressed around and pushed down with my hands on the beauty covers where the bolts weren't tighten down all the way and the sound was definitely muted considerably. I tighten the two bolts down nice and secure (maybe 1/2 to 3/4 of a turn) and the engine noise was considerably less. 🙂 Of course the next test will be to take the boat out and run it up to the 3200-3400 RPM levels and determine if the chattering noise has been eliminated. I strongly suspect this will be the case.

I will post back later with the results.

 

[mspaugy]

that is interesting. I have been involved with Marine Diesel propulsion and auxiliary engines all of my adult life. Funny how most problems could be traced back to the last maintenance performed. Please do let me know if the noise is gone, curious now, lol.

 

[SEEKER]

I had the same problem, I figured it out when I found a rusty bolt in my bilge. Turned out it was, as you say...the bolts to the beauty covers. Soon as I re-installed and torqued it down a little she ran as quiet as a mouse Now I periodically check them for snugness.

 

[baz]

I had the same problem, I figured it out when I found a rusty bolt in my bilge. Turned out it was, as you say...the bolts to the beauty covers. Soon as I re-installed and torqued it down a little she ran as quiet as a mouse Now I periodically check them for snugness.

Well, thank goodness none of my beauty cover bolts have loosened and fallen out so far. I have yet to make a test run with engine running in the 3000 to 3500 RPM range to see if the rattling noise has been eliminated. Will do this over next week some time.

 

[Levitation]

The US military, and especially the air force, are currently wrestling with the issue of maintenance caused failures...
The air force has extensive statistics that reveal that the highest rate of failures on their aircraft occur during the first flight after routine maintenance has been done... They are now trying in selected units with forgoing the traditional scheduled maintenance based on flight hours and attempting to do inspection and repair on an as needed basis (IRAN) to see if that is an improvement...

As an airplane owner, I always hold my breath on the first take off after the annual inspection - and off the top of my head I would say that about half of the time I come back with a new squawk that was not there before the inspection...

 

[RProffer]

It sounds like the Air Force needs to get their Quality Assurance Team to do their job.

Whenever I have someone work on my car, boat, whatever, I try to look over their shoulder when possible, and I always eye ball their work afterwords. Many times I have found loose connections and parts, and you would be surprised how many free tools they left behind. When I find loose connections/parts and tools that were left behind, I never use that technician again.

 

[baz]

I had the same problem, I figured it out when I found a rusty bolt in my bilge. Turned out it was, as you say...the bolts to the beauty covers. Soon as I re-installed and torqued it down a little she ran as quiet as a mouse Now I periodically check them for snugness.

Well, thank goodness none of my beauty cover bolts have loosened and fallen out so far. I have yet to make a test run with engine running in the 3000 to 3500 RPM range to see if the rattling noise has been eliminated. Will do this over next week some time.

Well, I finally had the chance to test for the engine rattle issue two days ago. My 1st mate's sister was over visiting us from the UK for 3 weeks and the weather here in PNW area broke and last Tue was fair weather with some sunshine... 🙂 ... so we set out for Port of Poulsbo -- which is but a 75 min run at around 12 kts from our Edmonds Marina. We set off at around noon time without our two Fox Terriers as the younger one (named Jake) was only 4 months old and didn't want to burden 1st mate's sister with keeping him leaping about the boat and getting into constant mischief.

During the run to Poulsbo I opened up the RPMs to around 3200 and no engine rattles heard... great I thought. Now increasing RPM to 3400 and still no rattle noise. I then pushed RPMs up to around 3700 and still no engine rattle noises heard. Well this all seemed great... however, after settling the RPMs down to around 3400 the engine rattle raised its ugly head, but this time it was not constant as it came and went. The rattle was obvious to 1st mate who wanted to know what the noise was all about. I explained things and she seemed OK with my explanation.

I tried this same scenario with varying the RPMs between 3200 and 3800 and the rattle was always there at certain RPMs.

I'm hoping the rattle noises are simply caused by harmonics and some loose engine component rather than a more serious engine issue.

Thus, my test has showed the engine rattle is still present and I will endeavor to get a more professional opinion when I have the 250 hr engine service early next year before the summer season.

I'm obviously more than bummed out about this... 🙁

On the upside, my work in making the engine cabin step sealing from engine noise into the cabin was successful. The engine sound is greatly subdued in the cabin area and the engine noise is a nice sounding pure low frequency rumble and gives me confidence the engine is pulling strongly without issues. 🙂

 

[aginglawyer]

I had a similar experience, hired a diver and found that the propeller anode had eroded away enough to vibrate at certain rpms. Replaced it and problem solved. Carry a spare anode. Allan on Stout.

 

[baz]

I had a similar experience, hired a diver and found that the propeller anode had eroded away enough to vibrate at certain rpms. Replaced it and problem solved. Carry a spare anode. Allan on Stout.

Well I hope that is not my issue as that anode was replace but a month or so ago.

 

[Levitation]

Resonance rattles are common... Just had the 08 Duramax into the dealer yesterday, 3 rd time, for a buzz at the level of my left knee on the lower instrument panel... Said buzz only happens at slow idle (warm engine, in gear, with the brake holding the truck from moving... Raise the engine rpm even 20 rpm and the buzz stops... The mechanic says he thinks he got it this time - he said that the other two times :roll:

 

[baz]

...Engine rattle issue continued

Spent a few hours on the boat yesterday and worked/researched some more on the engine rattle noises.

Found two more beauty plate bolts weren't completely seated down.

One was on the top surface and was found with engine idling and me pressing down on the starboard side beauty plate. I could see there was movement between the bolt head and the beauty plate when I pressed down and engine noise/rattle diminished to almost zero.

The other was on the bow end of the engine -- one that has a rubber vibration-isolation bushing underneath. It was not that it was loose, but rather it was positioned so that the edge of the beauty plate was too close to a metal part of the engine. If this plate vibrated with just a slight movement it could be in contact with the engine's metal and cause chattering noises presumably. So I loosened this bolt and one on the stern side and rotated the beauty plate up maybe 1/8" to 1/4" to clear it from the engine's metal surface.

I really now feel I've solved this annoying problem -- but will not know for sure until I take the boat out for a quick spin while putting in through a range of RPMs.

later...

 

[JerryE]

The Yanmar mechanic that did my heater hose change out advised "losing" those beauty covers, which are diifficult to remove and hide lots of stuff you want to visually inspect prior to each trip. He explained the history of Yanmar's addition of these covers in engine evolution. In brief, too many idiots (read: owners) were stepping on delicate parts and breaking them. So they gradually grew to cover more stuff. R25's don't even come with a front cover as access is so limited to that part of the engine. The covers promote corrosion by trapping moisture, too. Finally they are quite heavy.

Who needs beauty in a tug! Pull 'em off an store them in the starboard under berth compartment to help counterbalance the left-side list on an R25.

 

[baz]

The engine rattles have been resolved. The final beauty plate bolt that was not seated ALL the way down was the main culprit. I took the boat out today and put in through 3000 to 4000 RPM in 200 RPM increments for several minutes each and not one rattle/chattering noise was evident.

SUCCESS at last. 🙂