Frustrations with new Vetus Engine Mounts

[kss1220]

This summer I tackled the project of replacing the original factory engine mounts that were at the end of their life span. The boat is the C34 1987 with the original Universal 25. I replaced them with the old mounts with new Vetus K50's.  While I was at it I added a PSS seal and new hump hose.  Since the modification I have had nothing but frustration trying to solve engine vibration issues at low idle speed only.  It was so bad that it sounded like the back end of the hull was coming apart.  Awful!!!!  Once the engine speed was brought up to 1200 rpm things the vibration totally went away both in gear and out of gear.  I will tell you the engine mounts were GREAT at the cursing speeds!  Much smoother than the original mounts. However when you come back down to 1200 rpm or lower it almost hurts your ears as the boat is crying out STOP!!!!!  The problem is I cannot set the idle speed at 1200 as the transmission will slam into gear at that speed.  I have checked to make double sure that the engine is running up to spec.  I thought maybe there was air getting into the fuel causing it to run rough at idle.  This is not the case.  Also it should be noted that I could grab hold of the engine by hand and I can move the engine side to side and make it simulate the awful noise while the engine is off as well (not as loud).  You can literally feel and hear the shaft hitting the shaft tube.  Alignment is right on almost perfect.  The orientation of the shaft in to tube is almost dead center at rest.  It was at that point I gave up and moved on to my next attempt to solve it.

After thinking about it for awhile and talking to a number of marine experts I came up with what I thought was a good solution at the time....
One of the other issues that reared its head in this  change over was that I could hear rubbing off the shaft on the fiberglass thru-hull tube as the engine accelerated.  Everyone agreed the PSS shaft seal was part of the cause.  The old stuffing box was stiff and it was more or less centered the shaft to some degree in the middle of the fiberglass tube. The PSS sort of just goes along for the ride as you only have the bellows to hold the carbon seal.  The short stiff hose on the stuffing box was sort of like a shock absorber if there was any movement of the shaft side to side. On the PSS because the new Vetus K50 mounts are much softer the engine moves more easily and when a thrust from the prop is transmitted into the engine the engine moves on the mounts.  Having only an 1/8 in. of clearance between the shaft tube and the prop shaft is not a lot of room.  To resolve this issue I fiber glassed a cutlass bearing in the stern tube right behind the PSS seal assembly.  This eliminated any chance of movement and wear on the stern fiberglass tube from the shaft.  My thought was that this would also eliminate the vibration and noise when at idle.  Unfortunately it worked to only eliminate the rubbing as it assured that there was no way the shaft could be off center at any time. The vibration still exists at idle.

All you Vetus K50 users out there, is there something I am missing?  DO you have the same problem?????

I am at a point I am thinking of pulling out the Vetus and ordering the original replacements from Catalina.  I hate to do so because the time involved.

Kelly

[Mike and Theresa Vaccaro]

Kelly,

We recently completed the same mod.  Additionally, we added a flexible coupling between the engine and the shaft.  We use a standard stuffing box.

Might be an apples/oranges comparison due to the flexible mount but at speeds above idle, there is little or no boat vibration whatsoever.  At idle, however there is some vibration.  Believe that's simply the nature of the beast (i.e., a 3 cylinder diesel is going to vibrate at low RPM).  Also believe most of vibration at low RPM is the result of SHAFT vibration.

Ideas that were the result of a conversation with the tech support folks at VETUS:

Check your actual RPM with some type of acurate, external tach.  Alternator driven tachs are notoiously innacurate.  It may (or may not) be possible to tweek your idle speed to eliminate SOME low-speed vibration.

Re-check the alignment.  (Learned a trick that works with a BULLFLEX coupling and might be adaptable to other flexible couplings as well--depending on design.  A fine machinist's square can be used between the aft face of the flange and the top of coupling that secures the shaft log.  If the engine is properly aligned, the aft face of the coupling and the shaft "holder" should be exactly perpendicular.  This is a "warm fuzzy" check that allows you to quickly check the alignment without unbolting anything.)

Consider installation of a flexible coupling if you don't already have one.  Please note that this won't cure low RPM vibrations completely, but will mitigate them to SOME degree and provide overall damping at all operating RPMs.

Don't over-pitch your prop.  Over-pitched props have a tendancy to compound lateral shaft motion.

One last thought:  All small diesel engines with a small flywheel vibrate at low RPM.  It's really a matter of whether you want the engine to vibrate in its mounts, or the boat to vibrate (i.e., stiff mounts or directly bolting a motor to the stringers)--or something in between.

Another question for the group is whether or not anybody has researched Hurth transmissions to find out what the RECOMMENDED shift range is (actual RPM)?  The operator's manual states that:  "The transmission is designed to permit reversing at full engine speed. TO BE USED ONLY IN THE EVENT OF AN EMERGENCY!"  As for reommended shift technique, it states:  "When shifting transmission, engine RPM should be returned to idle, then shift transmission firmly from one direction to another. A slight pause in neutral will allow propeller to slow and add life to transmission."  Ron Hill had some good thoughts on shift/IDLE control technique, i.e., run your engine at a speed where vibration is minimized, using low speed only as required to shift.  Guess the question is what did the engineers at Hurth consider to be IDLE RPM?

Please keep us posted on how things are working out with your boat, since we're all learning as we're going!  

Best of Luck,

Mike Vaccaro
"Spirit" '88 Hull 563

[This message was edited by Mike and Theresa Vaccaro on September 08, 2003 at 01:55 PM.]

[dave davis]

Kelly, what I am about to say will sound like an over simplification to you and to others, but I'll just have to risk it. I was about ready to get some new motor mounts and center the shaft like much of the news lately. My 1988 was sounding like a runaway hard rock band especially at 1000 rpm. Then,( on a cruise) I asked my wife to go down bellow and see if she could tell where most of the banging was coming from. To my embarrassment, as soon as she stepped on the ladder, 90% of the noise simply went away! Wow, I was amazed. Ya I know, I have not solved anything, but it sure made motoring much more pleasant. I don't do much motoring, in fact I just changed my oil at 75 hours and it took 24 months to put on 75 motor hours. I would say that 90% of the motor hours are used getting to and from the start line and with a full crew, we just never hear the motor.
I still may work at reducing vibration but it just is not on the top of the list. No, you can not borrow my wife to help your problem!!!

[tsoko]

Kelly,
A few years ago I read in Mainsheet a few articles about changing motor mounts, including one by Ron Hill.  Most of them mentioned the increased vibration at very low RPM's, and the willingness to put up with that in exchange for the smoother cruising RPM's.  I did a little more research and purchased the Vetus K75 motor mounts.  They are slightly stiffer than the K50, but softer than the OEM mounts.  I have been VERY happy with them.  I have slightly greater vibration from 800-900 RPM, but around 1000 it smooths out nicely all the way up the scale.  For me it's been a great compromise.  I only go to idle when shifting.  At all other times I'm at 1000 or greater, and the boat is quieter and smoother.  Just a thought.

[kss1220]

Further info.  I have recently replaced the injectors so I thinking that maybe Ron's idea of changing the rear mounts to K75's could be a good option.  I think I will try it and let you know.

[Jeff Tancock]

Hello Kelly,
I'm sorry to hear of your difficulties. I recently went through the same sort of thing, but all is well now.
A couple of thoughts -

1)The PSS is great because it allows you to check the shaft in the log by simply moving it up/down and back and forth when the shaft is no longer coupled to the engine measuring travel. Doublecheck the travel of the shaft in the log and the alignment at the coupling.

2)Check that when the engine shakes the muffler casing isn't being lifted and slammed as mine was. I didn't realise that the screws holding down the muffler were stripped and this made a horrible banging sound when I started and stopped my engine or idled too slow. It sounded like the engine block was slamming against the fiberglass mount rails. Very loud! You could also check for anything else that may be hitting like the exhaust riser agianst the muffler intake tube etc.

Keep looking - you'll find something amiss down there!

[Mike Smith]

Kelly -
This is off topic, but did you ever do the inverter installation?  If so, where did you end up mounting the inverter?  By the way, I was looking for your e-mail address in the database for #495 - is that you?

Mike and Jan Smith
S/V Breezer
www.mikejansmith.com

[kss1220]

Mike:

First here is my email address: ksteck@stanleyworks.com or k.steck@comcast.net.

I did complete the installation of my inverter and it turned out wonderful.  I have it tucked under the chart table and attached to the wall of the hanging wet locker.  The unit is out of sight and is hard wired into all the 120 volt outlets.  I installed a blue seas source switch that changes the 120 volt input from either shore power  or the inverter.  The inverter input is ran directly from four 6 volt Trojan wet cell golf cart style batteries. The batteries are located in the original battery locker.  I hand made a PVC battery box from 1/4 inch PVC sheet and heat welded the joints in the locker.  It will not come out unless you destroy the box but, the batteries are sealed with a lid and they are secure.  In addition I did not have to modify anything in the locker.  I have a thing for making sure everything on my boat stays stock. The inverter is a pure sine inverter from a company in Taiwan that my company does business with us for other inverters and electronic items.  The company private labels inverters for export into the USA to a number of companies.  I like this inverter for its compact size and long duty cycle. The inverter also has a power saving feature automatically powers it down into a sleep mode.
Interested in any more details let me know.  I would be glad to share.

[David Sanner]

Has anyone, as Ron suggested, changed their rear mounts to K75 and their front mounts to K50?

I would think that the softer mounts in the front would cause the engine to want to want to dive more in the front when shaking side to side causing stress and/or vibration.  Or maybe
it's negligible.

Has anyone compared directly the K50's to the K75's - first hand on different c34's?

It looks like the MITSTEUN are too tall, has
anyone successfully installed them?


I don't motor that much but it would be nice to lower the vibration a bit... but not at the expense of hard knocks when starting or shifting gears... or other issues like hitting the shaft tube.

[Mike and Theresa Vaccaro]

Sanner,

Might consider using the formulas that Vetus has developed for selecting mounts.  Also, they have a tech support center here in the States, so it's certainly worth a call.

We have 4 K50's on our M-25XPA ('88 model) and couldn't be happier with their performance.  We also have a Vetus Bulflex flexible coupling.  Between the two, we've gone from lots of vibration to none.  We don't have a dripless seal, just a plane old fashioned packing nut--which can be repaired with a piece of t-shirt in an emergency.  The key to making everything work well is proper engine alignment.  Even with the flexible coupling with can accept up to 3 degrees of "misalignment," it's best to align the engine to the standard .003 tolerance.  If you do that, things should work out well.

It's been a while, but if I correctly recall the math, the -25XPA (25 HP) was just about on the upper limit for the K50's.  Engine mounts are funny things...there is certainly no harm in going with larger/stiffer than required, but the trade-off is increased vibration.  If your engine in larger, and the recommended size with K75, then that's the way to go.  

The only downside to the Vetus mounts is that the holes in the base are not oblong or slotted, so it MAY be necessary to enlarge them slightly for alignment purposes.  The other option would be to fill the old holes in the limber mounts and re-drill.  Or, things might line up just fine with the existing holes...the Vetus mounts will require slightly shorter lag bolts since the base is thin steel vs. cast aluminum.  

Best of luck.

Mike

[cmyerchin]

Having just spent the last weekend working on my M25 engine, I feel compelled to add my experiences.

I re-powered my Catalina 30 from a 5411 to an M25 about two years ago.  Prior to the re-power I decided on the Vetus K50 engine mounts based on the positive feedback over the web.  I had read the reports of low RPM vibration but decided the pluses were better than the minuses.

I installed the engine (professionally rebuilt) and to a solid coupling aligned to .001".  The coupling, the shaft and the 3 blade 12" prop were all new and taken to a machine shop to ensure proper balancing before installation.

The low RPM vibrations are very bad.  The poor little engine jumps around on the soft mounts like a carnival ride.  Hover ever, once throttled out of idle the engine quickly smoothes and runs quiet with little vibration.  I decided to just live with the low RPM vibrations.

We use our sailboat about one to two times a week for 4 month(s) a year with an extra 2 week trip to the San Juan's annually.

Two years later....

Last year I noticed oil in our normally clean bilge.  Looking all over the engine I thought the leak was coming from an oil drain hose I had installed though the engine's drain plug during the re-power.  The only way to get at the plug was to pull out the engine.  Last weekend I did that.  Not a small task in a Catalina 30. 

What I found was not a single point oil leak but every gasket at bottom of the engine was leaking.  The bottom of the timing chain cover, the oil pan, and the oil drain hose.  I also found the alternator bracket had a crack and the heat exchange bracket had cracked.  All the coolant hoses around the engine had worn points were they contracted anything other than the end connections.  In fact the water inlet hose to the water pump had worn an 1/8" off its bottom side where it was in contact with the engine bay floor.

Its clear to me the low RPM vibrations are shaking the engine to death.

I re-torqued the oil pan and timing cover bolts and I've ordered the K75 mounts.  I decided on the K75 mounts because they have the same footprint as the K50 mounts. 

I'll post again once I've installed the new mounts see how the engine vibrates at low RPMs.

[Indian Falls]

My problems with the engine mount "upgrade" are chronicled in this thread: http://c34.org/bbs/index.php/topic,6386.0.html   

There has been no solution for me so far. 
If I hadn't sawed the original mount studs off, I'd have put them  back in.

So far there has been no improvement from injector cleaner.  I just put a new hump hose on this winter. 

I will very likely pull my injectors for cleaning but... waiting to see what others have found to be the culprit before I tackle that.  Not really convinced on that one.

[Paulus]

I had my injectors rebuild 2 years ago.  A very significant difference in vibration and noise. 
Paul

[cmyerchin]

Thanks for the reply and a link the alternate thread. 

After reading your thread I'm going to cancel my order for the Vetus K75 mounts.

I'm not too sure about the injectors.  My engine starts fine, runs clean, and does not knock (improper fuel detonation) at low RPM.

In thinking about the problem, the Vetus mounts have a lot of rubber between engine and the mounting surface.  I see this as a double edged sword. On the positive side there is a lot space to dissipate and isolate the vibrations of the engine.  On the down side when engine shakes at just the right frequency there is enough space for things to really get out of control. 

The design of the old mounts have a lot less rubber between the two mounting surfaces.  This "should" limit how bad vibrations can get the when the engine vibrates at critical frequencies.  On the down side more vibrations transferred to the hull.

Looking on the web I see a mount recommended for M25 engines:
http://www.thermoboat.com/polyflex-Univ-m25-hzf10m.htm
The mounts look like the originals.  Thus should limit how bad variations can get.  I've placed a call with the site owner and left a message.  Has anyone else had experience with Poly Flex mounts???

Only found one entry on www.ericsonyachts.org  where someone commented (positively) about them.  Has one else tried these mounts?

[Ron Hill]

Dan : If rebuilding the injectors/new injectors doesn't solve the problem, then try the Vetus K75s (especially in the rear.