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Old 11-01-2007, 18:55   #1
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Engine mounts - When to replace?

My friend tells me engine mounts have a life expectancy. Mine are 25 years old. Should I replace them? Do they need to be replaced. Where do I get new ones at?

Should they be heavier than or same as what's on there?

Never needed to think about this before so I'm out in the woods (ocean) hear.
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Old 11-01-2007, 19:28   #2
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25 years? I think they are about due. The same age as mine when I replaced them. The rubber was still good but the steel was rusty. Even though rubber materials can still have a shelf life. You never know where a crack might be until it's too late.

Using the same mount as your old one should be sufficient considering they lasted this long. Mounts are specified for different weights of motors. In a roll over it'll have to carry the weight of the motor but yet be soft enough to absorb the viberation.

Their is some new rubber (generic name) mounts out now with a kind of transparent look that are suppose to be better but of course more expensive too.

These seem to be the most common....................._/)


Fisheries Supply Search: engine mounts
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Old 12-01-2007, 02:28   #3
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Bushings Inc. - Motor Mounts
Marine and Industrial Engine Mounts: Manufacturing by Bushings Inc
Cross-Reference by Engine: http://www.bushingsinc.com/model1.html
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Old 12-01-2007, 14:00   #4
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There is a specific difference between automotive engine mounts and Marine engine mounts. Marine do not rely on the rubber to take the wieght of the engine in a possible situation of an angle of more than hroizontal. A marine mount has to be able to be captivated by the metal braket that is fused to the rubber block. So if the engine is inverted, the metal braket relise on it's captivation so as the entire engine weight does not pull on the rubber/vulcanised joint.
An engine mount should last many many years. But oil contamination, heat and excessive vibration will cause early deteriation and failure. So mounts should be placed on the list of other items annually inpsected.
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Old 12-01-2007, 15:41   #5
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Engine Mounts

During my re-fit (re-powering as part of the process) I mounted engine on Poly Flex mounts. They are a polymer based product and they have a range of mounts, couplings and other products all made from the same material. They have a range to suit most applications/engines etc

One of the advantages of using these mounts is they will electrically isolate the engine from the hull; especially if you use a poly flex coupling as well.

Poly Flex Home Page

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Old 13-01-2007, 04:49   #6
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Rules of Thumb:
- Engine only vibrates excessively in neutral - check your motor mounts.
- Engine also vibrates in gear - check your alignment.
- Mounts must be completely supported by engine bed rails.
- Mount studs should be perpendicular to the engine center line.

You might consider installing a drive shaft system that incorporates a thrust bearing and/or CV joints (the effects of torque produce thrust and load transfer on the mounts).

The engine must be very precisely aligned to the propeller shaft. The thrust of the propeller has to be absorbed by the engine and its mounts.


“Sail Boat Auxiliaries” - And Why They Don't Last as Long as They Should”
by David Pascoe
”... The Bushings, Inc. Mounts supplied with most diesel installations are just not adequate. There is a new mount out, with which I’m very impressed with the design, and is supplied by Caterpillar on all their engines. Unfortunately, I don’t recall the name of the manufacturer, but you can contact any Cat dealer to find out ...”
Goto: Marine Engines: Sail Boat Auxiliaries at Dockside Reports

”Drive System Alignment” ~ by David Pascoe
”... The most common reason (why Drive Systems Go Out of Line) is that over time, the engine mounts wear or sag ...
... if the mounts are the vertical stud type set in rubber in an aluminum base, these are the kind that are prone to rocking back and forth, particularly with heavy diesel. Check the stud to make sure that its centered in the base with the vessel at rest. If its leaning in any direction, the mount is stressed and the system is out of alignment (see photos above ).
Conduct a back down test. It takes two people to do this, one person operating and one observing the mounts and engine. Observe the point where the engine bracket attaches to the mount. One engine at a time, start from neutral, put the engine in gear and then accelerate hard, up to about 1/2 throttle for several seconds. Stop, then repeat this process in reverse, all the while watching the mounts for movement. Repeat several times. If the engine and mount are moving more than 1/8" in any direction, your mounts are not doing their job of holding the engine in place ...”

Goto: Marine Engines : Drive System Alignment by David Pascoe, Marine Surveyor

Pascoe recommends “Ace Mounts”:
Ace Mountings Co., Inc. Marine
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