.... new and newer is nice. But if the logic is based on cost, or cost/return, the only reason to replace with new is if the old rig no longer does what you want (to your satisfaction), or it has become unreliable (to your level of satisfaction). Other than those reasons, new replacement will always cost you more. So in that regards, assuming current set up meets your needs, the extra cost will only be of value as much as you feel nice(r) about new gear.
One thing I know, it’s only new the first time you use it!.
Re the repower, if it’s well maintained and reliable, why would you? Unless reliability is becoming a concern. Your 1700hr motor probably will not depreciate a lot in the next 1000hrs of use, but a new one definitely will a lot in its first 1000hrs if use. Fuel savings would be hard to justify in that equation..
But reliability concern is something only you can value.
Oh, and we all know, fish is usually cheapest by the kilo from the local seafood shop. However, arguably less fun...
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