Vertus Engine mounts

[DaveM]

Over several years I have seen several discussions on k50 vs k75 mounts for a M25xp.  There has been mention that K50s are pretty soft and K75s are pretty hard.

Ron I recall you setup with K50s forward and K75s aft. Do you still consider that the best combination?  You also mentioned that you had to file out the holes that mount on the stringers. My original mounts are about 1/8 in off the stringer bolts. Do the flanges have that much latitude to file?

Anbody else that has installed these mounts on this engine have current ideas? 

Thanks Much
DaveM

[Ron Hill]

Dave : I had the 50s in the front and the 75s in the rear - everything was much better than the all K50s.

When I installed the K75s 4 or 5 years later I found that I did not have to elongate the lag bolt holes -- Vetus had already done that. 

[Indian Falls]

I just put K75's on all four corners.   I am not very happy.   The engine shakes a lot below 1200 rpm and the .003'' flange setting on the prop shaft coupling means nothing if the motor is moving around +/-.150'' while running.  I'm being conservative, it looks like .25''

Like you I studied every post concerning this issue.  I was expecting to not know the engine was running when standing on the dock like one of the other members who posted his results.

If I run the rpm up so it's smooth, then the trans shift slam and power applied to the water is quite significant.  Not acceptable.

From the cockpit it seems real nice above 1500 rpms but a look in the engine compartment tells a different story. 

Now I wish I had put in K100's, but I don't know how hard they are either.  The originals were like rocks.  The engine never moved.  The K75's are very soft.  I went with them due to the input on this forum concerning the K50's. 

I do not have a hump hose or a flex coupling.  Now I'm concerned that the added vibration on the exhaust system is going to cause me some headache in the near future.

I thought I had everything tight enough and believe me, I'm an old wrencher and this is not my first rodeo, but the first few minutes of operation at what otherwise was nice idle speed loosened up one of the mounts and moved the K75's under the lag bolts.  The lag bolts do not have enough purchase to hold this down under these conditions.  I did not use shorter lag bolts, I ran them into the stringers the rest of the 1/2''.
Should of had some good bite that way. 

A side note:  I did not lift the engine for this installation.  I cut the studs with a hack saw and replaced the mounts one at a time with the engine in place.  The vetus mounts separate but are a bear to keep the top shell from turning and torquing when you tighten them up in place.  Hence my loose mount problem above. 

I'd really like to find a set of mounts that are 75% as hard as the originals and put them on the rear of the engine and possibly leave the K75's on the front. 

The end result is this:  I have my idle set for 1100 rpm up from 850, the noise/vibration is horrific,  same as the old mounts.  I'll only be at this rpm for short periods so I guess I'll live with it.  Anything above this is smooth and quiet from the cockpit.  I most likely will post more comments after I've been out motoring and docking a few times.

Has anyone checked their alignment some hours later to see if everything stayed in place/aligned?

PS:  The engine runs great, no problems there,  any thoughts that it shakes badly due to burned valves, bad fuel, low compression etc... are hard pressed to accept.

[DaveM]

Dan & Ron. Thanks a bunch.

I wonder why such a difference in experience?  Are y'all both running M25xps with old style stuffing boxes?
Ron you have not mentioned it but do you see a lot of engine movement down below when cruising as Dan mentioned? 
Thanks
DaveM

[Ken Juul]

Dan,
Perhaps it's the engine that is at fault not the mounts.  Dirty or fouled injectors cause excessive vibrations as can tired diesel.  Might want to run some injector cleaner through the engine and do a test run with new fuel to see if there is any difference.

[Indian Falls]

Thanks Ken,

I'll run some injector cleaner but the engine did not vibrate the whole boat with the old mounts, it just rattled the stairs too much when cruising and at an idle it was normal in my book.  You knew it was running but it wasn't alarming like it is now.  The new mounts allow it to slap the prop shaft in the cutlass bearing and that's where the horrific noise is likely from. That doesn't mean I have a lot of axial play in the cutlass bearing any play will make that noise.  This M25xp has 1400 hours it starts easy, makes no other noise,  and the old stuffing box.  If I look in the compartment under the head sink the exhaust riser connection is vibrating like crazy, it does not look like it's going to hold up that way for long.  Nor does the wiring under the exhaust manifold.  I balanced the weight on the mounts this way:  On the back, you count the nut revolutions that it takes to transfer all the weight from the port mount to the stbd mount.  Then back off half.  That should split the weight pretty close between them. It was 5 full turns on the rear.  It will be different on the front, there is less weight.

I had a thought today that the K50's might compress under the weight more thus limiting movement, just a thought..

[Kyle Ewing]

Dan and Dar,

I had a similar experience when I replaced mounts on my 1990 (hull #1010) with M25XP this spring.  I replaced the original mounts with K75s on the back and K50s on the front.  I aligned the engine with the boat on the cradle.  The day the boat went in the water it ran extremely smooth at all RPM settings.  The next day it knocked and vibrated below 2000 RPMs so I guess the hull shape changed in the water.  It did run smooth over 2000 RPMs.  I adjusted the alignment at the coupler but it wasn't much better.  I was almost ready to accept that this was reality with the new mounts, but it still didn't seem right.

After reading many articles/posts on engine alignment and spending several hours on the boat, I found the shaft wasn't centered in the log and the engine was about less than 1/4" too low, even though the coupler halves seemed to be in alignment.  I determined this by moving the shaft at the coupler up and down and side to side to determine how much room I had and raising the engine accordingly.

After doing this, all knocking is gone and it's much smoother below 2000 RPMs.  Running it at dock there's still a little vibration above 2500 RPMs so I may have more alignment work, or it vibrates by nature when pulling on the dock lines.  I'll know the next time I take her out.  Noise level is much less than before, but you can still tell it's running.

I found this interesting article on engine allignment from yachtsurvey.com:  http://www.yachtsurvey.com/Alignment2.htm.  I quoted part of the article below.  This helped me to understand what was happening.

The Nature of Inboard Drive Systems  It is a common belief that engines and shaft couplings have to be aligned to tolerances of a few thousandths. There is some misunderstanding about this. Yes, the shaft coupling to transmission coupling needs to fit within several thousandths, but what were talking here is the coupling fit, not the shaft alignment. This is an important distinction that is often confused. I'll explain why.

A conventional shafting system is essentially a free-floating, semi self-aligning system. How's that? Well, because the engine is mounted on rubber mounts, and the shaft is mounted in rubber bearings. Of course rubber being soft, that means that both the engine and shaft can and do move. See my point here? Since neither the shaft nor the engine is held rigidly in place, there's not much point in attempting to perfectly align the shaft with the engine, is there? No, because if everything is approximately aligned, the shaft will tend to self-center as a result of centrifugal force. The fact is that conventional shafting systems will tolerate a great deal of intolerance because of these factors.

The truth is that it is virtually impossible to correctly align engine and shaft with the methods that are commonly used. Because of the rubber mounts, the engine will not be in the same position when running as it is when stopped, when the alignment is made. Propeller thrust and engine torque will cause the engine to change position. And since the weight of the shaft sitting on rubber cutless bearings causes the rubber to compress, the shaft is not in alignment with the bearings anyway. When the boat is running and the propeller spinning, the shaft will align itself (but not if the basic alignment is out).

Regarding engine mount selection, I talked to a Vetus dealer on K50s vs. K75s.  He said K50s were sufficient for our engine/transmission given the weight and the K75s might be too stiff.  I went with the K50/K75 combination based on recommendations here.  Could you have a bent shaft or another problem the older, stiff mounts masked?

[Ed Shankle]

I replaced my mounts with the K50's all around about 6-7 yrs ago, before the 50's in front and 75's in the rear became the standard advice. I also added the Vetus Bullflex shaft saver. Between both, the vibrations definitely smoothed out; no more stairs and cockpit sole rattling. Below 1000 rpm's is another story, but we've been warned many times on this forum, that the m25xp shakes your teeth out below 1000; just the nature of a 3 cylinder engine, I guess. No need to go below 1000 anyway. Adjust the set screw to bottom out at 1000.
I also changed my injectors 2 yrs ago and noticed another level of smoothness.
If you are getting the vibrations you refer to in neutral, then shaft alignment really wouldn't have any impact. Also, verify your tach. I found mine to be off 200. Doesn't seem like much, but when that engine goes from 1000 to 800, there's a whole lot of shaken' going on.
Good luck,
Ed

[Roc]

I have a flexible coupling.  Search this site for "Federal Flexible Coupling" and you'll find the info and pictures.

[Indian Falls]

Thanks for the input guys.  I hope all this helps the next guy.

I don't see any wobble in the prop shaft, not when it was in the cradle and not inside under the aft cabin.

My tach may be pretty close.  I'd be happy to set it 1200 but, If I put the tach at 1300-1400, I'm doing 4knots in the harbor (the cruising sweet-spot is between 2200 and 2300).  That's quite a bit of thrust and you don't want to shift it in-out of gear at that setting.  But those are the numbers it now likes to be smooth at in neutral. 

I shifted in and out of reverse and forward while tied up and it just seems like the wrong thing to do at that RPM.  I'll get the tach output verified this week.  I agree with Kyles quoted info. If you are .003" at the flange, which is 3'' in diameter, and if the cutlass bearing is 48 inches away, then the misalignment at 4 feet is only .095".  I'm not certain the cutlass bearing is mounted in rubber on these, but the stuffing box is only 6" away from the flange, and it's flexible.  You just don't want the shaft to touch the inside of the log.  I think the .003" is to protect the flange from stress damage, not to be the indicator of overall shaft alignment.

I'll have to see If I can find a way to align it better. I was shooting for .002" when I first started but then when the motor shook the mounts under the lag bolts I couldn't get it anywhere near that afterward.  I am most surprised by the huge difference in range of motion between my old mounts and my new ones.  The stuffing box looked blurry there is so much movement at 1100rpm. 

By the way, I never mentioned that my old mounts look like new.  There is no oil damage or tearing or de-lamination.  I would have put two back in but they're trashed now since I sawed the studs off to get them out.

Adding these to the list:  injector cleaner, tach calibration.

[DaveM]

Reading the surveyor article brought a thought to mind last time the boat was out and was part of making a difference. The rudder was dropped, shaft & cutlass out. I aligned the engine so that the center of the trans coupling was visually in the center of the strut. Bore siting if you will. The old mounts had compressed so there was a lot of adjustment.  I was concerned about this because the old cutlass was worn top to bottom front to back and the shaft and stuffing box was very worn where the aft end of the stuffing box is. After bore aligning and putting in new cutlass, shaft and stuffing box I realigned the coupling faces trying do most all the movement in the front mounts. Things seemed a lot better. I am replacing mounts as they are 20 years old and very compressed and with y'alls experience feel I can still get some more vibration at cruse out.

Appreciate the good discussion.

Goodwinds
DaveM

[Ron Hill]

Dan : I agree with Ken, the engine sounds like the problem NOT the mounts.

It just might be worth your while to change out the injectors - not that hard to do.  The engine should run smoothly at a hi idle (12-1300rpm) and not move in the mounts.   A thought

[Indian Falls]

Hi Ron, Ken

Are there any other indicators for injector problems that cause rough idle?

Smoke/soot?

Stalling?

Low power?

Hard starting?

I really don't want to open that can of worms without something a bit more definitive.

I was unable to beg borrow steal a shaft tachometer for this weekend, also could not get the time to run some injector cleaner through it. 

I did however take it out of the slip and move about the harbor,  there is way too much thrust at 1400 rpm for this to work.  If i pull the throttle back to 1100 for shifting the rattling is intense, much like the engine is not bolted down.   Then I put the throttle up to smooth out and there is way too much thrust, very difficult when docking and seemingly very hard on the trans if shifting at that rpm (around 1450?).  It is fairly smooth at 1100 rpm until you put it in gear.  Idle needs to go up to 1200-1250 to avert that problem.

I ordered a hump hose today and I even considered buying another set of motor mounts from Bushings Inc.
They appear in every way to be the same mount that came out.   

As a side note, There is less than 15 total minutes of run time with the new mounts and already I had to chase a loose connection at the engine because it would not crank when pressing the start button.  ( I pulled and poked while the wife repeatedly tried the start until it began cranking. )

However I really trust you guys and I'll explore any suggestion before  I go ripping those V75's out and offer them for sale here!!

[Mike and Joanne Stimmler]

I recently replaced my motor mounts with the K75's along with a new soft rubber hump hose and had a definite improvement in the vibration at all rpm's.

Mike

[Ron Hill]

Dan : I'd say that the symptoms of needing new injectors are ; loss of power, rough running and some soot.

The injectors in your auto are constantly being cleaned as gasoline is a solvent.  The tips of the diesel injectors get carboned up which screw up the spray pattern and even the pressure.  You can take your injectors and have them checked for the pressure they "pop" at and the spray pattern.  The last time I had injectors rebuilt the cost was about $45 each and new ones were about $55 each.

You'll definitely notice the difference in engine performance.  Well worth it if you've never done it.  Look in the tech notes as there are a couple of articles and changing injectors .  A few thoughts