Hi Dan,
Been going through all these systems on our 2003 since we got it a couple years back. I had the saildrive seals changed last season and ended up needing to replace the lower unit due to pretty bad pitting along the seal seat thanks to electrolysis. While I won't likely touch those seals for another 15yrs in fresh water and with proper anode replacement (unlike previous owner who didn't have the yard change the upper one), I would highly suggest changing lower unit oil at least every other year. That way you will know if the prop shaft seal is going bad. When you drain it, any water or froth would exit first, which is a sign of water intrusion from a bad seal or running over fishing line, etc.
If you do saildrive seals, this is the easiest time to do motor mounts, otherwise, just re-torque them.
Check keel bolt torque, one of mine was only slightly beyond hand tight
Mixing elbow is always worth checking at that age and I'll likely pull mine this winter as it looks original.
Inspect steering cable by using some oil on a tissue to see if it snags on any broken strands.
Rebed stanchion bases and any original deck hardware as this is a Jboat after all and soggy deck core can be prevented. In ours they did use some impervious material for core where the bolts pass through, but a couple were starting to leak. Rebed with Sika 291 or equivalent. I found soggy core in the aft cover behind the steering pedestal from water freezing in that groove each winter and causing cracks there. That was removed and remedied from underneath, so topside nonskid was left intact.
Rod rigging can be dye tested for cracks, but as long as your turnbuckles are in good order, that rigging is built to last a lot longer than 15yrs under normal usage, especially those that have the terminal ends peened on.
I changed my primary winches over to Harken Performa this past year as the drums were smooth and Harken turnaround on re-surfacing is currently around 12 months. I sold my original ones on eBay for $1k. Performa drums can easily grip with only 3 wraps, even in big breeze, which was a huge upgrade for my mostly short handed sailing.
Inspect roller furler carefully as the screws holding the track sections together on mine fell out about 20ft off the deck, which was a big headache during a sail change when the track separated and the sail jammed. Those should be installed with locktite red.
Check/ replace all sheaves in the mast and boom. Links to the proper ones are on this site via search. The plastic gets brittle in the sun over time.
Pretty sure I could find others, but that is the list I have been chipping away at as I hope to keep this boat for a long time.
Todd
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