Engine vibration and drive savers.

[mariner2k]

Hi, I have an mercedes OM 314 80 hp for and engine. While operating the hull has a little too much vibration for my liking. I should also mention that this occurs when the engine is not in gear. When in gear it varies normally with RPM. There are sweet spots and not so sweet spots. In any event I was thinking of adding a drive saver to lesson the vibration through the shaft, not from prop vibration, just to have something else to absorb vibration. I had one on my last boat, but that was a much smaller engine (4-107) and wasn't too bad anyway.
Any thoughts on vibration or drive savers would be appreciated.

[Gary E]

No idea what a "drive saver" actually is but you might start with some vibration damping motor mounts
http://www.bushingsinc.com/

[GWB]

If its doing it in neutral then new motor mounts might be in order - unless the motor is running really roughly
Drivesavers help when in gear

[mmd]

A DriveSaver is primarily a device designed to shear apart if your propeller suddenly stops - i.e., hits or snags something. By destroying the DriveSaver, your gearbox and engine are spared damage. They do absorb some vibration, but not much and mostly in the higher frequencies - in the hearing range, not the feeling range.

If you want to stop engine vibration through the hull, you have to isolate all contact points between the engine/gearbox and the hull. This entails flexible mounts, no hard pipe connections, and - most germane to this topic - a soft coupling on the gearbox output flange. The problem is that a soft coupling cannot absorb the thrust from the prop acting on the shaft. Therefore, you need to install a thrust block and bearing between the engine and the shaft, with a stub shaft - usually a Kardan-type shaft - connecting the thrust bearing to the engine via the soft coupling. This takes up a fair bit of space, so is not normally in the purview of small sailboats, and is a fairly fundamental bit of structure, so it is a bit of a job to do. The results, however, are spectacular; virtually no vibration in the hull at all. The Bounty replica Catriona, pictured on the "l Francis h" thread, has this system installed and one almost has to look at the instrument panel to see if the engine is running.

Bottom line: Will the adddition of a DriveSaver lessen the vibrations that you feel from your engine? Yes, a little bit, but probably not as much as you would like. I would reccommend instead that you check your shaft for proper alignment and straightness, refresh the engine flexible mounts, and isolate all connections to the engine via hoses. And tune your engine - the smoother it runs, the smoother your ride will be.

A heavy rubber mat (and I mean heavy) laid on the hull in the lazarette above the propeller will dampen a lot of prop-induced vibration in the hull, but in a wooden boat it also traps moisture beneath it. If installed, regularly lift it so that the wood below gets some fresh air & dryness. Bottom paint or red lead paint under the mat is good insurance, too.

[mariner2k]

True the shaft alignment should be checked as a mater of practice. However that doesn't affect the idling vibration. The mounts are around 20 years old. I'm not sure how long they last. I understand that a drivesaver type device will save your gearbox, but will it not create a break between your gearbox and hull?
MMD I'm not familiar with a thrust block. If you have any more info on that, I'm curious. As far as any solid contact between the hull and engine, There isn't any. Just the mounts and shaft. Everything else has been installed with vibration in mind.
Regarding a tune up: what can be done to make a diesel run smoother? This may sound off, but the engine seems to run smooth even with a hand on it, but I'm sure that is not the ultimate test.

[carioca1232001]

.......what can be done to make a diesel run smoother? This may sound off, but the engine seems to run smooth even with a hand on it, but I'm sure that is not the ultimate test.

Some 4-cylinder in-line engines have a contra-rotating mass coupled to the crankshaft to dampen out vibrations arising out of reciprocatory action.

Big difference between the 'haves' and 'have-nots', although this is not something that can be retro-fitted on an engine.

In addition, turbo-charging makes for less erratic combustion and consequently, turbo-charged engines are a lot quieter than their naturally-aspirated counterparts.

[paladin]

In your present configuration, the prop turns, drives the shaft, and the boat is pushed forward by the thrust acting on the engine/transmisssion which is tied to motor mounts.......
By installing the thrust block/or partial bulkhead/whatever in the hull and then connecting the engine to the shaft through a flexible coupling....the power is transmitted directly to the hull at the thrust block, the load is taken off the engine, and the engine may be mounted on relatively soft flexible mounts to greatly reduce the vibration. The coupling also allows for an up to 5-7 degrees of misalignment with no ill effects.

[carioca1232001]

In your present configuration, the prop turns, drives the shaft, and the boat is pushed forward by the thrust acting on the engine/transmisssion which is tied to motor mounts.......
By installing the thrust block/or partial bulkhead/whatever in the hull and then connecting the engine to the shaft through a flexible coupling....the power is transmitted directly to the hull at the thrust block, the load is taken off the engine, and the engine may be mounted on relatively soft flexible mounts to greatly reduce the vibration. The coupling also allows for an up to 5-7 degrees of misalignment with no ill effects.

R&D (brand name) engine mounts are pre-loaded in the factory to restrict fore-aft movement , while simultaneously allowing for sideways movement.

Haven´t used any, but on paper at least, they seem to be good candidates for a future acquisition.

http://www.randdmarine.com/enginem.asp

[mike48]

tRY

[mike48]

FWIW, try these folks, I have used two sets of their mounts on 2, DD8v71's with tremendous results in reducing vibration, and hence perceived noise. They also sell the R&D mounts and drive savers. I believe their web site is www.pyiinc.com (http://www.pyiinc.com)

PYI Inc.
12532 Beverly Park Rd.
Lynnwood, WA 98087
425-355-3669

[andrewe]

After 20yrs, it might be worth jacking up the engine carefully to see if the mounts are still good. Not unusual to look OK but be worn out, or possibly the rubber/metal joint failed.
A

[Lew Barrett]

Chuck's advice (backed by Michael's) is the logical answer. Since adding thrust bearings and some form of drive isolation where they don't exist is not trivial, I'd follow mmd's advice first regarding the condition of your running gear and the state of tune you are now enjoying (or not).

Soft mounts by themselves will be only half the equation, since a rough running or poorly balanced mechanical package will continue to transmit a great deal of vibration back to the structure at the first hard contact point. However, doing all the easy stuff first, including a general tune up, then checking the shaft (and wheel) is still the recommended course. Checking for worn or broken mounts is next. Those can be replace in situ, and if you find the solution is still not adequate, at least you have eliminated all the basics and are down to making a decision about just how far you are willing to go to resolve your problem. Of course, on an aging package, it could be a combination of all the basic problems, with the final refinements of isolating the entire package being icing that may or may not be necessary to meet your requirements.

[carioca1232001]

One of the inventions of the outstanding British polymath and engineer, Fred Lanchester, was a vibration damper for IC engines :

http://en.wikipedia.org/wiki/Frederick_W._Lanchester

His invention is still in vogue with MB 4-cylinder, automotive diesel engines as the following C&P attests:

'....The camshaft, Lanchester balancer and the ancillary assemblies are driven by a combination of gearwheels and just a short drive chain...'

http://mercedes-benz-blog.blogspot.com/2009/03/new-mercedes-benz-e-class-part-ix.html


Lanchester´s balancer can be found in certain truck diesel engines as well, as for instance, the Motoren Werke Mannheim (MWM) Series 10 4-cylinder diesel engines.

The OM 314 (MB) 4-cylinder truck diesel engine at the heart of this thread is unquestionably a most reliable and sturdy workhorse, although the mechanics at my Yacht Club are unanimous in pointing that it does vibrate a lot

Installing adequate motor mounts could help mitigate the vibration being experienced.

[BBSebens]

Seems like they covered all the bases.

I would like to suggest Hydraulic motor mounts. They are a fluid filled mount that will pull out a lot of vibration. Though it sounds like you need that thrust bearing too.

I work in a shop that services raspberry pickers. they run on small diesels very similar to those found in most of our sailboats. after 3 to 5 thousand hours, they get tired and don't run like they used to. I can only assume that after 20 years you've accumulated a few hours. while your putting in that thrust bearing, have the motor taken to a shop and thoroughly serviced, if not rebuilt. I dare say that will smooth things out and even gain you some economy. would be a worthwhile investment at this time.

[Gary E]

Hi, I have an mercedes OM 314 80 hp for and engine. While operating the hull has a little too much vibration for my liking. I should also mention that this occurs when the engine is not in gear. When in gear it varies normally with RPM. There are sweet spots and not so sweet spots. In any event I was thinking of adding a drive saver to lesson the vibration through the shaft, not from prop vibration, just to have something else to absorb vibration. I had one on my last boat, but that was a much smaller engine (4-107) and wasn't too bad anyway.
Any thoughts on vibration or drive savers would be appreciated.

How old is this instalation??? or is it a new motor and installed for the first time??

If it's old as I suspect, then you dont need a thrust brg, a thrust brg is already in the transmission.
You need a smoother running engine, get it timed, tuned etc, and better motor mounts.

It never fails to amaize me that everyone assumes that you need "stuff" now that it didnt need 10 or 20 yrs ago.

[carioca1232001]

Seems like they covered all the bases.

I would like to suggest Hydraulic motor mounts. They are a fluid filled mount that will pull out a lot of vibration........

You beat me to it, although I was skeptical about the availability of heavy-duty ones !

However, it looks like the following outfit could actually be carrying the right stuff:

http://www.fraserbronze.com/mounts.html

One would need to pitt these against R&D´s mounts, or better, have an experienced hand give his opinion. One thing that comes to mind is the durability of the hydraulic ones.


Though it sounds like you need that thrust bearing too.

Unlike automotive/truck gear boxes, most marine gear boxes are equipped with thrust bearings, though having an external thrust bearing would help to shield the latter.


I work in a shop that services raspberry pickers. they run on small diesels very similar to those found in most of our sailboats. after 3 to 5 thousand hours, they get tired and don't run like they used to.

3 to 5 thousand hours ? Man, these are nearly as indefatigable as heavy-duty truck diesels !

[carioca1232001]

.....It never fails to amaize me that everyone assumes that you need "stuff" now that it didnt need 10 or 20 yrs ago.

And vice-versa, in that elegant solutions conjured up a century or so ago and which have withstood the test of time, are so sparingly deployed in today´s world !

[mariner2k]

I have no idea how long it has been since there has been a valve adjustment or timing check or any general mainentance, so I will start there. Probably won't check the mounts untill the fall, It is not unbearable, just annoying compared to the old boat and 4-107. The engine fires right up and runs very well, but that probably doesn't mean it won't vibrate. Gary I belive this is an original install. The boat is only 20 years old but the OM 314 engines are much older.

[Gary E]

Lets come at this from a fresh direction....
Lets say you live in an area where they dont maintain the roads so good and the potholes have to get the size of a Volkswagon before they think about fixing it,
How long are your cars shock absorbers going to last?... 20 yrs??
I doubt it..
Engine motor mounts act like shock absorbers, GET NEW ONES.

[Lew Barrett]

Not to add fuel to the "thrust bearing" requirement, which I am unconvinced is necessary here, but the thrust bearing in the tranny has little to do with vibration isolation per se. It is there to take the torque and thrust of the wheel as it is transmitted back down the pipeline. It isolates the "drive" component from the wheel from the load going down the drive shaft (in the "opposite direction, so to speak) to the wheel, as in a standard marine application, the thrust from the propellor is transmitted to the engine mounts to drive the boat forward. That's why soft mounts by themselves are relatively less effective on a boat than they would be in a car. But the operative is "relatively." A bad mount(s) will certainly not be good for smoothness or durability so this is a case where attending to all of the items up to and including the mounting scheme makes good sense.

A separate thrust bearing feeds the drive directly to the boat and is absolutely critical if the full benefits of an isolated drive system is being contemplated.

But I don't advocate for that. Too big a job with too little potential return if the rest of the easy stuff is attended to.

[mmd]

Agreed, Lew. First make sure the engine is running as smoothly as possible, then ensure that the isolation mounts are adequately sized and still in servicable condition. Isolating the sterngear from the engine (installing a thrust block, bearing, and Kardan shaft) is the ne plus ultra in vibration reduction, and only for the most serious desires for smooth sailing. I was just trying to make the point that a DriveSaver won't cut down on much low-frquency vibration.

Gary E, the installation of a thrust block and bearing is to isolate the engine completely from the hull structure to cut down on hull-transmitted vibration, not to compensate for any percieved deficiencies in the engine manufacture, nor to merely make innocent boaters pay more money than they need to, as your comments above seem to imply.

[donald branscom]

No matter what you do there will be some vibration.

The prop saver/isolater will help, and is a good idea.
Also put a two piece split collar on the shaft so the prop shaft cannot back out.
Check engine - shaft alignment.
Check the prop to make sure it is balanced.

The alignment can change with time and some boat hulls ca twist etc.,.
So maybe you need a torque restraint of some type on the engine.
IT is called a damper. Looks like a shock absorber with a connection point on both ends.

[Gary E]

Gary E, the installation of a thrust block and bearing is to isolate the engine completely from the hull structure to cut down on hull-transmitted vibration, not to compensate for any percieved deficiencies in the engine manufacture, nor to merely make innocent boaters pay more money than they need to, as your comments above seem to imply.
I know that's the intent of that "thrust block"
BUT,,, this is a 20ish yr old install of a SMALL only 80 HP engine, that for the first 20 yrs has run just fine..
In my opinion going to the expense of installing a new gaget and that assumes there's room for it, is wasting time and money trying to cover up a problem instead of fixing the problem.

In other words...
Lets put some lipstick on this pig,
but it's still a PIG

[Lew Barrett]

Oh well; it's hard to make everyone happy, isn't it?

[ben2go]

The absolute best way to get any engine to run smooth,is to drop some coin on a balance and blue print of the reciprocating internals.Also having the injectors blueprinted will help with noise and vibration.

[mariner2k]

Okay. Some of this is getting a bit over my head. Easpecially when we get to balancing the internals and injectors. Are there simpler steps to begin with in tuning a diesel, or is all of that an intrical part of it?

[Lew Barrett]

Diesel tune up:

Clean Fuel, filters and pumps working. Valves adjusted. Clean injectors, and properly timed fuel metering. Check for good compression if that is suspect. That in, you're pretty much good to go. Check the mounts and running gear. Minimal run-out on a true, straight shaft, tight, good running properly aligned engine with all struts and supports in good nick, and with any bearing surfaces within spec. True, well balanced wheel. That's about all there is outside of potentially costlier repairs or improvements.

[ben2go]

Okay. Some of this is getting a bit over my head. Easpecially when we get to balancing the internals and injectors. Are there simpler steps to begin with in tuning a diesel, or is all of that an intrical part of it?


I was kinda taken it to the max with the statement I made earlier.Comes with building a lot of hipo engines.I do agree with Lew Barrett on giving the engine a good diagnostic once over and tuning everything up.Doing a balance and blue print would be great if you were overhauling or rebuilding the engine.Sorry for any confusion.

[mariner2k]

Sounds like an easy place to start. I can put the bottle of scotch down now. All of what Lew has mentioned I have done before to other engines. The old stuffing box was replaced with a dripless one a few years ago. I don't appear to get any increase in vibration when in gear, so I have a feeling that some aligning was done then. Though I'm sure the prop needs cleaning.

[donald branscom]

Sounds like an easy place to start. I can put the bottle of scotch down now. All of what Lew has mentioned I have done before to other engines. The old stuffing box was replaced with a dripless one a few years ago. I don't appear to get any increase in vibration when in gear, so I have a feeling that some aligning was done then. Though I'm sure the prop needs cleaning.

Wait thats it! Just get a bottle of scotch and it will smooth everything right out.

[mariner2k]

I suppose I should have asked , What is the best scotch to reduce engine vibration?

[jimmy]

I understand some small boat transmissions (well mine at least) rely on thrust from the propellor to work properly. If you install a thrust bearing on a boat with this type of transmission it might have unintended consequences. Just something to consider.

[Lew Barrett]

Jimmy, I doubt he's considering an isolated drive system from what I have gathered.

[mariner2k]

You gather correctly. It is way down on the list. I'll probably start with a valve adjustment and injector timing. After that I would probably look at engine mounts. I don't know if these are original or not. The boat is a 1988, but who is to say that they were put in new.

[will tracey]

Oil change, valve adjustment, and fuel and air filters are the keys to a smooth running Mercedes diesel. You really shouldn't have to mess with the injection pump unless someone else did (and let's hope they didn't). Also, I have found the engine likes the max glow-plug warm time (until the relay kicks) before starting.

Please contact me if you have any more questions, I have a bunch of good resources.

[mariner2k]

Will, I agree on the injection pump. This engine doea not even come equipped with a glow plug. I'm not a diesel efficienado, but from what I read they say this engine didn't need one for some reason. ( I'd like to know why?) I can vouch for that, because even with temps in the teens, it started right up How often should valves be adjusted on these?

[ben2go]

No glow plugs usually means high compression ratio.I'm not sure how many hours of run time before the valves should be checked.I am anal so I would do it in the spring with all the other maintainence.

[Lew Barrett]

Will, I agree on the injection pump. This engine doea not even come equipped with a glow plug. I'm not a diesel efficienado, but from what I read they say this engine didn't need one for some reason. ( I'd like to know why?) I can vouch for that, because even with temps in the teens, it started right up How often should valves be adjusted on these?

Glow plugs are pretty much a thing of the past. Modern engines start based on the more accurate atomization and metering of their fuel, which is injected when the combustion chamber is heated by the force of compression. The newer plants are equipped with pre-heaters for use on exceptionally cold days. I've never needed to turn my heaters on in cold weather, either, although I am told that if you run bio-Diesel, the probability of needing to use them goes up on the coldest days.

[ben2go]

Bio diesel gels at low temps.Not something I would want to run in a boat.

[will tracey]

I second Ben's opinion on biodiesel. Mercedes engines are extremely well engineered and well built. They are not, however, designed for bio. Stick to dino.

I'm not familiar with marine versions of these engines, but 60's technology certainly can't be considered "modern". I have a 1985 3- liter 5 cylinder Mercedes engine in my car (an '85 300 TD wagon) and the glow plugs are definitely an important part of the equation. The engines in that series (123 made from sometime in the 70's until 1985, I think) are extremely durable, and I would suppose the marine versions made in the 60's are as well. Long story short, I would make sure there aren't glow plugs. Diesel needs air, heat, and compression to combust, so to me it makes sense not to leave one third out, particularly when the block is cold.

[Lew Barrett]

I don't run bio, nor do I have any plans to. Not the least of the drawbacks is that, if bought at the pump, it costs more than the dyed fuels sold in Washington State.

In addition to it's cold weather drawbacks, it can be slightly more corrosive, and it won't do older hoses or rubber parts any favors. But people do and will run it, especially on the west coast where it's available at the pump, including the pumps at Shilshole. In a mild climate such as we (usually) have here, biodiesel will do OK on a boat since temps rarely drop below freezing, and in any event, it's possible to heat an enclosed vessel, unlike a car which if kept outside is victim to whatever weather comes by. They say you shouldn't run a previously dino fueled boat on straight bio in any case, but there is an outfit in town that is converting Euro equipment (I believe they are starting with the VW common rail motor) for straight bio-fuel use. Personally, I'd prefer a standard conversion or marine engine from a larger manufacturer.

But the simple matter is that for most people, it's not really a practical proposition.

BTW, If you start with glow plugs, you'll need 'em. Otherwise, you don't. It's pretty straight up.