Welll... Maybe it's worth it...
I replaced the motor mounts on both my '77 H27, then the '86 H31 I got about 9 years ago. Did it because they were looking kind of ratty, and had been stressed by removing the engine(s) a few times. Engines tend to bind on the mount threaded studs when lifting them. (I use a come-along attached to a 4x4 across the top of the companionway). They are very durable mounts, and probably the most benefit I got was psychological by just having new ones. If yours are showing deterioration and you want to replace them, it's a fairly easy job. Use a 4x4 across the companion way at the top. Attach a come-along to it and to the engine. You will have to disconnect the exhaust at the mixing elbow. If mixing elbow is badly rusted, this is a good time to replace it. Disconnect the shaft from the engine, and all the electrical connections. Remove the nuts holding the engine on, and lift the engine out. Go slow, and jiggle the engine after each pull, as it will probably bind on the studs. The new mounts will be labeled 'front' and 'rear'. Adjust the nuts that the engine will sit on, on the new mounts, to the same height on the studs as on the old mounts. Remove the old mounts from the boat and check the screw holes, as you may need to epoxy or otherwise repair them if worn. Install the new mounts. Set the engine on the new mounts slowly. Be careful not to damage the threads on the studs on the new mounts. Mounts and mixing elbow are available from Mack Boring, 800-622-5364. Good Luck!
