Motor mounts and engine alignment change over time

[Kyle Ewing]

Last season I started to notice some vibration on my 1990 C34 with M25XP with 10 year old Vetus motor mounts.  Although it's still not bad, it's worse this season, especially at mid RPMs.  Previously it was super smooth.  Mounts are firmly bolted to the stringers and cutlass bearing is tight. 

Should I try to realign the engine to compensate for changes to 10 year old mounts, replace them due to age or look for another cause of the vibration?  Engine has 2000+ hours.

[KWKloeber]

Not look for ANOTHER cause, determine THE cause.  [size=78%]It could be engine mounts, in which case replace them - you cannot adjust for worn out / sloppy mounts.  Really, if they are worn, how would you "adjust" them to compensate for slop?   [/size]



Cutlass being tight doesn't necessarily mean it's properly aligned.  It might just not have worn out yet.       

[Kyle Ewing]

Thanks, KWKloeber.  My thinking for adjustment is  the engine would sag or otherwise shift over time.
Adjusting it to compensate might extend mount life. Sounds like that isn't the case.

Is 10 years (about 800 hours) the life I should expect from Vetus mounts? 

My other suspicion is injectors as they've not been changed in the nearly 20 years I've owned Donnybrook.  Engine has the same power and no increase in smoke as measured by soot near the exhaust, even after motoring a lot this summer.

[mark_53]

Previously it was super smooth.

I've never heard of a M25XP that was super smooth.  My motor mounts are 31 y/o. 85 db behind the helm, 89db in front of open companionway. There is vibration around the 1800-2000 rpm range than smooths out around 2200. Maybe your prop needs to be checked?

[Ron Hill]

Kyle : You didn't mention which of the Vetus mounts you have??  Even though Vetus recommended the K50 for the weight of the M25XP, I found that they were too soft and changed to the K75s. (especially in the rear mounts)

The M25XP is difficult to change the oil filter and not spill oil on the right front mount - with out taking specific precautions to protect that mount.  I wrote a Mainsheet tech note article on how to protect that mount while changing the oil filter.   Also if you have dripped any internal coolant (50/50 Preston mix) on any of the mounts that tends to soften the "rubber"!!

You can easily remove the injectors and take them to a truck diesel engine repair and they will check the spray pattern and the "pop" pressure - usually free!!

You also might re-check your engine/shaft alignment.

I assume that your prop is in balance and has not been damaged/no bent shaft?

A few thoughts   
 

[KWKloeber]

Thanks, KWKloeber.  My thinking for adjustment is  the engine would sag or otherwise shift over time.
Adjusting it to compensate might extend mount life. Sounds like that isn't the case.

Is 10 years (about 800 hours) the life I should expect from Vetus mounts? 

My other suspicion is injectors as they've not been changed in the nearly 20 years I've owned Donnybrook.  Engine has the same power and no increase in smoke as measured by soot near the exhaust, even after motoring a lot this summer.

Kyle
Typically the worn mounts allow actual movement, no longer just dampening vibration (actually "isolating" vibration - they're called "engine isolators" - typically the actual bracket bolted onto the engine being the "mount."  But there's different nomenclature depending upon which circle one frequents). ;-)
So if yours are close to metal on metal (isolation gone, so transmitting vibration to the stronger) then there's nothing that adjustment can do.  But if the engine is out of alignment or a bent shaft or whatever then that could be another cause. That's why I suggest troubleshooting the CAUSE before deciding on the cure. 

Troubleshoot-troubleshoot-troubleshoot, then repair/replace.

[scgunner]

Kyle,

If your motor mounts are only ten years old it's doubtful they need replacement, mine are the originals and I'd be willing to bet most C34s still have their's. They are in fact adjustable, if only slightly which is all that's needed to align the prop shaft. You can raise or lower the motor as well as tilt it fore and aft. As already mentioned the first thing I'd do is check your shaft alignment.

I just recently removed one of my motor mounts to replace sheared mounting bolts, I was surprised at how good it's condition was, the rubber was soft and pliable and showed no signs of cracking or being dried out, although I'm sure there has probably been some sagging. I think I am going to replace them with the K75s pretty soon, but then my current mounts are 35 years old!

[Ron Hill]

Kevin : If you have the original engine mount, You'll be AMAZED when you switch to the K75s.  No more "buzz" in your feet during/after a long motor!!                     
You'll wonder why you didn't do it sooner !!

A thought

[scgunner]

Ron,

I'm getting ready to pull Top Gun out to have the bottom paint done. While she's out the plan is to replace motor mounts (K75s) along with the cutlass bearing and that black rubber packing gland tube plus whatever else we find that needs attention, as you know there's ALWAYS something you didn't plan on.

[Kelley Dean]

Had a similar issue with increased vibration a few years ago. Have an '88. Motor mounts not too old and in good shape. Checked alignments multiple times. Would run smooth over 1500 rpm. Had the original injectors rebuilt. Still having issue. Finally found that the glassed deck pad for the Aqualift was detaching from the hull. Repaired pad and all is well.

[waughoo]

I love hearing these found solutions in a thread about what someone expected to be motor mounts, but ened up being something completely different.  It provides a source of things to check when searching for a solution that might not be immediately obvious.  Thanks for posting your outcome.

[Ron Hill]

Guys : When I redid my engine mounts I also found that the muffler had debonded from the hull.  I just went and replace the muffler and rebuilt the muffler platform (wrote a Mainsheet tech note article on that find!!)

That's why I recommend owners look at those old Mainsheet tech notes, because most of the "new discoveries" have been already found and written up in the C30, C34 or C36 Mainsheet Tech Notes !!

A few thoughts

[Stu Jackson]

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That's why I recommend owners look at those old Mainsheet tech notes, because most of the "new discoveries" have been already found and written up in the C30, C34 or C36 Mainsheet Tech Notes !!

I recommend that folks do this, too.  But from what I see and read here on a daily basis, new issues arise more often than not.

Continuing the tired refrain that everything has already been found and written up is counterproductive and misleading, and discourages continuing discussions, which is antithetical to the purpose of this forum.

I try to provide links for earlier discussions if they apply to new questions.  While I have not and will most likely never match the sheer quantity of your invaluable documentation of the Catalina 34 over the years, I have written my own fair share of repairs, forum posts with photos, and many tech notes.  If someone asks about something I know about, I post a link to something I believe could be helpful.  in fact, I developed the entire set of 101 Topics for just this reason.

Our goal should be to maximize content and encourage questions.   Please stop telling folks it's all been done before, because there's always something new.

[Ron Hill]

Guys : Sorry for my comment.  Guess that I'm one of the few that realize that the C36 and C34 have nearly identical systems and later on the C30s and C28s have the same engine.

Stus' correct the form is to encourage questions.

A thought

[Kyle Ewing]

SOLVED!  Problem was a loose engine mount nut, the port, rear top one.  I somehow missed it on my initial inspection.  I tightened it and vibration was much improved.   I still need to make sure other nuts didn't move and check alignment but so far seems like an easy fix.

Lesson learned:  Make sure to double check the easy stuff first and don't assume the worst!