Thanks all for the informed responses. Someone did point out this topic had been covered briefly in a forum on a different site that had missed our initial searches. One respondant on that site had a similar experience with his years on a Catalana 25 with an 8 hp motor and was of the opinion that a 6 hp would probably suffice but the 8 is the smallest you can get with electric start. Other than that:
Thanks for the welcome! No we did not buy this boat from Beaverton. Have to look that up to see where it is....
To be clear we are not looking at removing a perfectly good diesel motor and replacing it with an outboard. However, we knowingly bought this boat with a Westerbeke W33 with 4k plus hours and in questionable condition. Some quick research at the time suggested $15k at the absolute low end to repower and close to that for a full rebuild. In our neck of the woods I would be surprised if we got away with $20k. Yet in a day or two I could install a bracket ordered on line and an 8hp outboard obtained locally and be on our way with less than $4k. And I do understand you still need to remove the old engine, shaft, etc. but not until you want or need to. As for resale value I know you never will recover $20k of addition spending put into $15k boat! It will still sell for $15k, may 2K more or it may be a faster sale, but you are still out most of your investment.
There are advantages and disadvantages to what I am suggesting. No more 50 amp alternator, dealing with gas instead of deisel fuel (although do that anyway because of the dink motor), and yes, less thrust and "bite" of the bigger prop and slower turning shaft. But you gain space, ability to carry more weight, much, much easier and cheaper maintenance, quieter operation (yes!), more local parts and expertice, and in a pinch you can swap out a bad motor for a new or used replacement in a few hours from anywhere! I speak here from the experience of 4 years with a 22 Hughs with 2 cycle 9.9hp, 15 years with 7.5m Tanzer with 7.5hp 4 cycle, 4 years with Bayfeild 29 with 15hp Yanmar diesel, and 8 years with Marine Trader 34 with 120hp FL diesel. Three sailboats and a semi desplacement trawler sailing mostly in the North Channel, Georgian Bay and Mackinac staights area. The worst was the B29 with the Yanmar... had everything from big sailboats with small outboards to kayakers pass us in channels, pain to maintain and winterize, and when we had a serious problem we couldn't get a mechanic to come to the boat, and of course couldn't move the boat without a very expensive tow, haulout and 'land tug' trip. The performance and enjoyment of this boat was worse than the Tanzer in just about every way, mostly because of the inboard diesel.
Lastly, as sailors we did not move to the trawler side for speed. Six knots in the direction you want to go (i.e. no tacking) is like warp speed to us. We are not interested in doubling hp (and/or noise) to get 8.5 knots out of a semi displacement hull designed for 7 knots.