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View Full Version : Engine Mounts ? silent killers?



mwert72655
10-15-2008, 10:20 PM
So what's the consensus on engine mounts in older hatterases. Is it possible that engine mounts can deteriorate to the point where they ruin a transmission without significant vibrations being detectable first?

Would you expect a qualified surveyor to detect this kind of problem at sea trial or not?

mike
10-17-2008, 12:02 AM
The simple answer is Yes & NO. The orig DD mounts are not robust, and sagging mounts will KILL the transmissions and running gear. I have over 50 pics of our 53MY's running gear to prove it. Few if any surveyors will pick up the problem. We had two surveyors on board one for the engines and gears, and one for the general boat, and they both missed it. Having said that I also missed the problem, it's very subtle to detect. One clue is if your props don't turn in N, you should be able to rotate the shafts by hand without the need for a bar or some leverage device. Another clue is finding reddish-brown contaminated oil being thrown from between the trans coupler/flange area. If you are really concerned, decouple the prop flange from the trans flange. The true mid point of the shaft should not fall below the mid point of the trans coupler. You can locate the mid point of the shaft by pulling up on the shaft and measuring the position to a known reference point, followed by doing the same in the down position. Repeat the measurements a couple of times to get a feel for the upper and lower points and take the best repeatable average. The true shaft center line will fall in the middle of the two reference points, which should correspond to the center line of the trans coupler, assuming all is aligned correctly.

OldLimey
10-17-2008, 06:11 AM
When Sundowner (42 LRC, 1981 vintage) was surveyed this year our surveyor did pick up on the state of the DD 4-53 engine mounts. She said that they were in poor condition and should be replaced at the next major overhaul. Basically the rubber has definitely stretched and the mounts have been shimmed several times to adjust. However, the shafts still rotate by hand in neutral and the packing doesn't seem to leak so the alignment isn't too bad.

We will replace the mounts at sometime - does anyone have any recommendations for new mounts to suit 4-53s? Sams has the originals but they are costly and we would like something cheaper and better if possible.

Thanks.

Boatsb
10-17-2008, 06:47 AM
I believe the 4 53's have velvet drive transmissions. Thats why the mounts can have some rubber to take out the vibrations while the 8v53's I have with TD's have solid mounts. I would put back the same type as they lasted 25 years and probably will probably be the best choice.

mischief
10-17-2008, 06:50 AM
On our 42'LRC MK1 we have replaced the original Hatteras engine mounts with "Soundown" adjustable mounts. The mounts were approximately $75.00 each. New brackets to connect the mounts to the engine yokes were made locally at approx. $65.00 each. Installing the new mounts took about 1 hour each. We are very pleased with the result.

I can fax you bracket drawings and adustable mount details for the 4-53 installed on LRC 42'.

Cheers,

Hans Knoepfel
"Mischief"
Jacksonville, Florida

REBrueckner
10-17-2008, 08:25 AM
Anything is possible, but generally speaking solid mounts used for many 71 series engines are usually either ok or cracked. And an owner who pays attention should be able to detect vibration...and investigate. An engine out of alignment for any reason, mount or otherwise, should provide telltale vibration...but different people have different sensitivities and such vibration may have unrelated causes...like a bent prop blade.

When underway if you put your hand on your transmission or observe the transmission carefully by eye you can usually feel or see any transmission vibration/movement that would be damaging...a related way is to place a small piece of wood on the transmission...to insulate your hand from the hot transmission....compare port and starboard for relative movement.

Slight to moderate vibration of a shaft to transmission coupling will usually wear the rear transmission seal over time, hence the possible oil spray mentioned above from the spinning shaft by Mike.

robertm
10-17-2008, 08:27 AM
What is the best preventative measure to take in order to avoid an engine mount problem in an early 80's 53 MY with original 8-71 engines and allison gears? So far, things seem to check out OK, but I would like to know if there is a recommended way to strengthen the original mounts to avoid a problem, or is replacement the only solution? It looks like it would be a pretty big job to replace them. Thanks.

Brian Degulis
10-17-2008, 08:45 PM
Silent Killers no Over looked yes

All rubber mounts deteriorate and compress over time. A lot of our boats have the Ace mounts I've never seen one fail. They are heavily constructed compress the least hold the engine firmly in place and last forever. The down side of them is that they provide very little in the way of vibration isolation enough to prevent damage from vibration but not much more.

The other rubber mounts are all pretty much the same Barr, Soundown , PYI , and Bushings Inc. are all very similar. They do provide good vibration isolation but they are more prone to settling and failing than the Ace. A neat trick to get good vibration isolation with a minimum of movement and good strength is to use more of a softer mount instead of fewer of a harder mount.

If you have rubber mounts you should separate the couplings and check the alignment every 200 hours or so. If you have recently installed new mounts you should check the alignment after the first 30 or so hours of operation most of the settling occurs within that period. You should check the rubber for cracks or movement except on the ace mounts because the rubber is not visible without removing the mount.

Replacing mounts is usually not that big of a deal if you think it through. Sometimes the engine can be jacked up just a 1/4' or so and the bracket can be removed from the engine allowing the mount to slide free. This goes pretty quick you need only split the couplings the rest of the engine can remain connected.

IMHO Hard mounting is a big mistake. Some feal it keeps the engine rigidly aligned which it does the problem is vibration. 4 cycle engines vibrate at a low frequency (thump thump) 2 cycle Detroit's vibrate at a high frequency (Hummmmm). You almost never see a 4 cycle engine hard mounted because the low frequency vibration feels bad like something wrong. High frequency vibration doesn't feel near as bad which is why you see some DDs hard mounted. The problem is that high frequency vibration actually does more harm than low frequency vibration. So you run the risk of having things loosen up or break even though it feels OK.

Brian

bobk
10-20-2008, 01:46 PM
How do you determine if you have Ace mounts? My 1981 48MY with 6V92's looks like it has no rubber in the mount, but I guess it might be inside.? It is almost impossible to turn the shafts by hand, but I have no vibration since betting the props reconditioned.

Bob

Chateau de Mer

Brian Degulis
10-20-2008, 09:34 PM
How do you determine if you have Ace mounts? My 1981 48MY with 6V92's looks like it has no rubber in the mount, but I guess it might be inside.? It is almost impossible to turn the shafts by hand, but I have no vibration since betting the props reconditioned.

Bob

Chateau de Mer

They look diffrent than other mounts go to this link http://www.acemount.com/ 3rd and 4th from the left will be what your mounts look like if they are Ace. The rubber is inside the rectangular steel housing it can only be seen if the mount is removed.

Brian

bobk
10-20-2008, 09:48 PM
They look diffrent than other mounts go to this link http://www.acemount.com/ 3rd and 4th from the left will be what your mounts look like if they are Ace. The rubber is inside the rectangular steel housing it can only be seen if the mount is removed.

Brian


Mine look like the sixth from the left, so guess it is an Ace. I have three cutless bearings per shaft, maybe that explains why they are hard to turn by hand.

Bob

SKYCHENEY
10-20-2008, 10:17 PM
Bob,
I have 3 bearings per shaft, Ace mounts, Allison M20's, and PSS dripless logs. The shafts turn by hand and I changed the cutlass bearings out 2 years ago. Maybe the standard shaft log makes it harder to turn than mine (assuming that is what you have).

yachtsmanbill
10-20-2008, 10:23 PM
While on the subject of mounts, two of the four on my westerbitch are gonners. The rubber donut is missing! Can these be replaced without buying new mounts? I would like to replace all four. ws

SKYCHENEY
10-20-2008, 10:26 PM
Bill,
I bought some rubber donuts about that size at Napa. They had a catalog with all different sizes and thicknesses.

chris
10-20-2008, 11:48 PM
Mine look like the sixth from the left, so guess it is an Ace. I have three cutless bearings per shaft, maybe that explains why they are hard to turn by hand.

Bob

Bob
My 48MY has the Ace mounts, 6th from left. My shafts were hard to turn by hand until I repacked with Gortex. I also replaced my log hoses. They turn easy now and are dry. I also repacked the rudders with Gortex and it made a big difference in steering, much easier.
Chris

bobk
10-21-2008, 07:29 AM
Bob,
I have 3 bearings per shaft, Ace mounts, Allison M20's, and PSS dripless logs. The shafts turn by hand and I changed the cutlass bearings out 2 years ago. Maybe the standard shaft log makes it harder to turn than mine (assuming that is what you have).


Sky, I have a dripless log as well. The bearings show no wear, either now or when the boat was surveyed in June 2006. Should I be concerned? What else might be at issue?

Bob

yachtsmanbill
10-21-2008, 07:57 AM
Thanks SKY... will check that out!
BOB... are you on the ground? Try a few drops of WD40 on the bearings. Dry rubber on steel is sticky some times. My new trans/alignment side turns very freely by hand and the OEM side (still new bearings tho) is a bit tighter. It still turns OK once its turning. Dry bearings?? ws

Brian Degulis
10-21-2008, 08:12 AM
The shaft should turn without a lot of effort. While in the water you should be able to move pretty easily with a 14" pipe wrench. But that's not really a test for alignment or mount problems you have to seperate the couplings that will tell the story.

Bill soft generator mounts are not very expensive and they go a long way to quiet things down. You might check McMaster Carr for the rubber make sure they're very soft. Also PYI or Bushings Inc for complete mounts.

Brian

ThirdHatt
10-21-2008, 10:00 AM
Bill, I replaced all 4 mounts on my 12.5kw Westerbeke on my 41tc because the factory ones were done. My mechanic got them for me, but they were only about $35 each. WELL worth it because it really helped isolate vibrations. I did not have a sound shield but the noise was not bad, it was the vibrations that I hoped to isolate. The new mounts did a good job.

bobk
10-21-2008, 11:41 AM
I'm in the water, but I think I can turn it with a 14" pipe wrench. When fresh pulled and bearings are still wet, it takes two hands on the 26" wheels.

Bob

stormchaser
10-21-2008, 12:04 PM
How much of a difference does wet vs dry bearings make? When we first pulled out, the guy power washing the [props spun them by hand, no problem. The next day I couldnt. Should I be worried?

Avenger
10-21-2008, 02:13 PM
You can't get an accurate picture of alignment on the hard. Boats change shape when they're blocked vs floating. For example, on mine, I had to shorten the stainless rubrail to make a repair. When it was in the yard I ground it to a perfect fit. On the water it was about 1/16" too long. Not much, but the thing clearly changed shape.

As Brian said, the only way you'll get a valid result is to seperate the coupling and measure the alignment in the water.

mike
10-24-2008, 01:36 AM
This a custom set of front and rear motor mounts for 8v71's in a 53'MY. I made these using the orig front mount plates, by welding 3/4"x3" flat bar to the old front plate. The rear mounts are made from 3/4"x6"x6" steel angle iron. The PYI mounts are HD 1" dia stud version, each is rated at 1000+ lbs. Both front and rear PYI mounts are bolted through the Al caped stringers into the orig Hatt stringer system. The stringers have a 1" thick plate imbeded in the structure running the full length of the engine pad area. These mounts really cut down on the vibration and noise transfer to the hull. Big improvement.

Brian Degulis
10-24-2008, 09:12 PM
Nice job!!! I removed the Ace Mounts from our 12V71s and replaced with Bushings INC. They are much softer than the ace I had to use more of them to get the capacity. It realy cut down on noise and vibration.

Brian

Carlos
08-16-2010, 02:59 PM
On our 42'LRC MK1 we have replaced the original Hatteras engine mounts with "Soundown" adjustable mounts. The mounts were approximately $75.00 each. New brackets to connect the mounts to the engine yokes were made locally at approx. $65.00 each. Installing the new mounts took about 1 hour each. We are very pleased with the result.

I can fax you bracket drawings and adustable mount details for the 4-53 installed on LRC 42'.

Cheers,

Hans Knoepfel
"Mischief"
Jacksonville, Florida


Mr. Knoepfel:


I am replacing the engine mounts on my 42" LRC Mark II. Would you kindly fax your bracket drawings and adjustable mount details.

My fax #is 703 379-9447.

Thanks

Carlos

cap1011
11-01-2010, 10:25 PM
Please fax drawings of 4-53 motor mount ears etc to
727-865-9359
Or email to ron1011@prodigy.net

Thanks
42LRC
Ron Bednarek

ron6785
11-02-2010, 08:45 PM
What is the best preventative measure to take in order to avoid an engine mount problem in an early 80's 53 MY with original 8-71 engines and allison gears? So far, things seem to check out OK, but I would like to know if there is a recommended way to strengthen the original mounts to avoid a problem, or is replacement the only solution? It looks like it would be a pretty big job to replace them. Thanks.Not sure about earlly 80's but 70's are solid mounts and are either fine or broken, so its pretty simple to detect. That does not mean however the engines are aligned as the shims over time corrode with a build up that can actually cause some alignment problems, Thru bolts/nuts are loose etc which affect alignment. A way to check is to loosen the shaft coupling and check for alignment after rotating the shaft several times. This should be done while boat has been in the water for at least 48 hours, as the hull can sometimes torque while in dry dock. Mine looked to be out of alignment after boat had been in dry dock for two months, however after sitting in the water for three days it came back in alignment and is fine.