engine mount life

[steven f.]

I'm getting some moderate engine vibration during certain RPM ranges on my boat, the shaft is not turning for this to occur. The engine is a 1985 westerbeke 21a with 1600 hours on it. The sound is not an internal sound, it seeems to be coming from the mount area. The rear engine mounts look kinda worn, I'm wondering what the life expectancy for a set of engine mounts runs. Sure hate to replace those rear mounts, in my 81 H33 there is not much room to get my fingers in there to do it with the engine still in place. This is probably a dumb question but it seems that the engine just sits on the rubber feet that are inside the mount. Is the engine somehow bolted down or does it just sit there??? We sailed in some nasty weather and seas and I never gave a thought to the engine coming loose and moving, what actually holds it down?

 

[Mike Turner]

Engine Mounts

Steven -If your engine mounts are original it's entirely possible they've worn to the point of needing replacement. It's less a question of life expectancy than if they've been subjected to oil, fuel, etc. that may have worn away the rubber. When that happens you'll get vibration, either from the engine no longer being securely held by the worn rubber, or by misalignment in the prop shaft, or both.The mounts basically consist of two components -- a metal "outer" part that bolts to the stringers in the hull, and the rubber "inner" part that the engine bolts to. Yes, the motor bolts only to the rubber part, but it's securely fastened to the metal part that bolts to the hull -- at least until the rubber degrades.Check to make sure that the mount itself is securely fasteneded to the stringer (this is where mine had trouble; just tightening it back up solved my vibration problem). But if the rubber is significantly worn it may be time for replacement.Good luck!Mike TurnerS/Y Amity

 

[Jerry Villines]

Change em

At roughly $100 each it is expensive to replace them but that really is the best answer when you get vibration when you know that you shaft, coupling, shaft bearing and strut are aligned. Usually when you cannot align the shaft the mounts are bad. Excess vibration will cause excess wear on your transmission, coupling, shaft and strut which can get very expensive. Yanmar says replace them every two years. In reality you can get a lot more out of them than two years. Good Luck.