I know, I know. It's been a while. Family, friends, commitments, responsibilities, work - doesn't leave much time for boat building, and even less for blog posting. But we'll catch up this week (it's worth the wait...).
So, on to today's post. In many older boats, and, unfortunately, lower quality boats, the engine mounts are lag bolted to the stringers directly, with the lags running vertically down into the plywood core. This method works fine at first, until the stringer core absorbs enough water to begin to rot. The water entry is inevitable, since there is no way to seal the penetrations with 100% certainty, over time. And, unfortunately, a boat built with this method of construction probably was not sealed that well at other penetration points either, so the odds in favor of water intrusion are quite high.
This is when the fun starts. Re-tightening the lag bolts won't work, and increasing their size is only a band-aid solution. Replacement of the stringers is the only proper solution. Depending on the age and value of the boat, this may or may not be a viable option.
A far better method for anchoring the engine mounts is the "L" bracket / backing plate combination. In this arrangement, an "L" shaped bracket is bolted to the stringer with horizontal bolts, which sandwich the stringer between the bracket and a thick backing plate. This method helps prevent water intrusion, due to both the orientation of the bolts, and the tighter seal established between the bracket or backing plate (and sealant, of course). Fortunately, later model Sea Rays employ L brackets. Unfortunately, mine were not looking too pristine:
Once everything had cured fully, I reinstalled the brackets...