Most engine mounts are taken for granted and as long as the engine doesn’t fall off the beds, most people think everything is fine. Mounts and their systems are as important as anything else in the drive system. These devices have to hold the engine secure while isolating vibration from the boat. They have to allow the engine some amount of movement but still maintain the alignment to the prop shaft. Most mount systems have some type of “cushion” system, usually employing either rubber or springs of some kind. Springs can “work harden” over time and break, while the rubber (or “elastomer” can deteriorate through oxidation or chemical degradation. Fuel or lube oil leaking onto an engine mount will swell and soften the cushion material causing it to fail. The pictures below show just that type of failure. If the rubber looks “swollen”, it may have been exposed to petroleum products. Compare the mounts with each other. It is unlikely that all the mounts would have been contaminated equally. Be sure to find the cause of the contamination before you install new mounts.
Over time, the threads and nuts on an adjustable engine mount can corrode and become inoperative when it comes to adjusting the alignment. Most alignments don’t take that long, between 1-2 hours. If the engine is out of alignment, beyond what the mounts can compensate for, it may take much more time to get the alignment right as we may have to move the engine around quite a bit. Corroded adjustment nuts are the most likely cause of excessive alignment times, so every so often, apply some type of corrosion inhibitor to the nuts and threads of the mount. It will save you money in the long run.