This is a great thread!
I love reading all the advice of how to fix a problem that hasn't been identified yet!
I've had boats off and on (Mostly on) for 50+ years on freshwater in the midwest. Keep in mind, most boats average running time in this area is about 30+- hours a season(You mentioned the boat is from Wisc, right?). Our season is only used 3-4+- months a year. If a boat is maintained, kept dry and out of the elements when not in use, they can last almost forever.
So a 40 year old boat in the midwest equates approximately to a 10 year old car! A 1989 Sea Ray (Sea Ray has always been a quality boat) with an Alpha 1 outdrive that only needs a couple thousand dollars or so(Interior repair/replacement can get expensive) or so to bring it up to safe, dependable, and comfortable condition in my opinion is a no brainer!
A new 18-19 foot SeaRay I/O with trailer would cost you 30K or better by the time all the I's are dotted!
First, Identify the problem!
Water in the bilge can come from many things. Engine drain plugs, Gimble hose Transom gasket, bilge plug, split engine hose, cracked head/block, loose bolt(s), split or cracked hull/transom, etc, etc.
First identify where it is coming from. A set of rabbit ears and a garden hose can be used to run the boat on land to make sure it isn't coming from the engine itself and that everything runs and works properly. Then install the bilge plug and run water into the bilge and look outside for leaks. Then, you can see what needs to be fixed.
Any loose bolts, nuts, screws etc are NEVER good on any boat.
Boats are fairly easy to work on for the average handy guy. basic tool skills is usually all that is needed. The internet and youtube can be a huge assistance! If your plans are to have a Marina do the work, my advice is schedule the work with them for the winter. It will make their lives much easier and therefore might save you some money!
We have averaged about 70 hours a year on our boat every season over the last 15 years and enjoy most every minute we are on the water! Its a 2008 I/O and looks almost like new. I keep it on a lift with a full canopy. It keeps the sun and rain off of it and allows the boat to dry properly after use. Covering a boat with a mooring cover is not the best thing immediately after use if the interior is wet!
Rain and sun are the 2 worst enemies of a boat when it's not in use!
These are just my humble thoughts on the subject.
Good luck with your project and please keep us posted on how you make out,
Ed
