6cta Motor Mounts – How to test?

[Gerasimos]

Purchased this 2001 Tiara 3800 with 6CTAs 4 years ago, these were the mounts on the vessel, not sure how far they date back but I am starting to wonder if they are good or not, the left motor seems to vibrate alot more than it used to under way.     Ive been reading some threads about alignment as well, anything obvious to look at or photograph to be able to tell? The props were fixed at my inspection survey, and I have not hit anything that I am aware of in the water. 

Topic

[Rob Schepis]

Could be prop(s) related.  When she was on the hard I would have pulled the wheels and had them scanned.

[Gerasimos]

Finally got back in the water yesterday. Cleaned down the growth on shafts and propellers before splashing

 

Looks like the “vibration” seems to be somewhere between 2000RPM and 2300 RPM. It seems to smooth out below or above that. Or, I don’t notice it as much below/above that.

At 1900 the boat runs smoother than ever but that could be placebo. 

Would a specific RPM range for vibration point to something in particular besides mounts?

[Gerasimos]

I’ve checked the propellers by “eye” and they look fine. I set up a block in multiple points to just barely clear one “fin” of the prop and then spun the prop to make sure they dont hit the block and it passes the check. The shafts feel good and tight. What is a good diy test to check shaft alignment?

 

As for the mounts, I am considering replacing just because of age and being proactive but wondering best DIY for this before. I am pretty handy, I do all the maintenance myself on both the mechcanical and electrical side, but something about removing an engine support has me shy

[Rob Schepis]

Yes, old mounts but don’t look terrible for their age but for sure the characteristics of the rubber inserts are not what they were when new.  As to vibration increase have you gone through the running gear and performed an alignment check?

[Tony Athens]

These are original Cummins supplied mounts (made by Hutchison/Barry) that are about 23 years old.. In so many words,  they have lost their MOJO and have collapsed  ( maybe overly relaxed is a better term) ——————  Our SMX BLUE  mount is an exact replacement also made by Hutchison/Barry  with a couple of SMX upgrades were willing to do for us. 

IMO, considering all, they are not that bad compared to most that I see that old

[Gerasimos]

Pics of the side of 2 of the Port Side’s mounts

 

 

[Gerasimos]

Thanks Rob and Tony.

 

Rob, I will get a pic of the side, figures I took a picture of every angle besides the relevant one.

 

Tony, are you able to tell those are original from the model/serial numbers. My concern is that if they are in fact originals I probably have lived out their life and need to replace them, but how am I able to tell?

[Tony Athens]

Besides what ROB said,  isolator  mounts could be looked at  as similar to automotive shock absorbers in some ways as   they need to  dissipate  the vibration energy from the  car bouncing around  and engine  ( heat)–Yours are original (20+++ years) and   may  have lived their useful life  so to say

[Rob Schepis]

Need side views of the mounts, like this, to see how the bottom of the rubber isolator is sitting within the cast mount.  Have you at least checked that all mounts are TIGHT ?  (at the studs and stringers)

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