BACKGROUND INFORMATION: On the SPORT 15 hull and other classic-era Boston Whaler boats the lower engine mounting bolts are a problem because the engine splash well is too shallow. Boston Whaler published special instructions for proper mounting of an engine in these shallow engine splash wells. See the FAQ answer at
Q8: How Does the Engine Mount to the Transom?http://continuouswave.com/whaler/reference/FAQ/#Q8and carefully read the section under the heading "Problems specific to Boston Whaler boats," and carefully read the advice given as "the fifth workaround."
Also read the REFERENCE article
Boston Whaler Dealer Bulletin 10-84http://continuouswave.com/whaler/refere ... 84-10.htmlI strongly recommend you follow the advice in the FAQ "fifth workaround" which is the best solution and the method recommended by Boston Whaler, by moving the engine to a one-hole-up mounting on the upper engine mounting holes, and then using the highest hole position in the lower mounting bolt holes on the engine. Once you read the Boston Whaler recommendation and the FAQ, you will have a better understanding of how to mount the engine, known where the lower mounting holes should be located, and learn what you should do about mounting a new engine.
THE CAUSE OF THE PROBLEM: the damage has occurred because the original installer must have over-tightened the mounting bolts, crushing the fiberglass.
ADVICE ON REPAIR: see two REFERENCE articles on proper repair methods for Boston Whaler boats. There are two articles, both illustrated.
Repairing Hull Damage the Whaler Way
by Taylor Clarkhttp://continuouswave.com/whaler/refere ... epair.htmlThis article shows a repair to hull damage following the methods recommended by Boston Whaler.
Also see
INSTRUCTIONS -- HULL PATCH KITShttp://continuouswave.com/whaler/refere ... tions.htmlThis article reproduces the actual instructions from Boston Whaler.
I strongly recommend you read both articles and study them for content and advice on making repairs. These are well-written, illustrated articles, and have been used for repair advice by many Boston Whaler boat owners. You will find they have very high information content.
WHAT RESIN TO USE: I recommend using WEST System Epoxy, and use one of their REPAIR KITS. The repair kit will have enough resin, hardener, filler, mixing bowls, and so on to make these repairs. The kits are an excellent value, are not expensive, and give you all the materials you will need. You need not worry much about color-matching gel coat for repair, as all of the repair area will be hidden from view, as long as you don't grind out a huge area round the hole. There is really no need to grind the surface away from the hole for fairing. It will just make a larger repair area.
TRANSOM WATER CONTENT: I cannot offer any speculation on the present condition of the embedded wood in the transom. However, be aware than any damage to the hull gel coat surface that exposes the underlying laminate or wood reinforcement will create a path for water to enter the inner hull. Since the engine splash well is designed to catch water, the damage at the lower engine mounting holes may have created a path for water to enter the interior of the transom.
The condition of the transom should be assessed before beginning any repair. You may find that there is more work to be done than you anticipate. You may decide to hire a boat artisan with skill in repair of Boston Whaler hulls to perform the work for you. Or, you may decide you can perform the work yourself. The worst case will be the transom wood has been wet, has rotted, has lost strength and integrity, and a more intensive repair of the transom is needed. The best case: there is no sign of water in the embedded wood, and you need to only repair the damage to the lower engine mounting hole on the splash well side of the transom.