[Bushwacker]

Your original question didn't fit your answer, so I changed the question to what I think you really intended to ask! There are really 2 separate issues here. 1. The one in the new title above. 2. New 4 stroke vs. new DI 2-stroke?

I think you've answered question 1, the new vs. old issue, pretty accurately! You'll NEVER be able to recover the cost of a new motor simply by a ~10% reduction in fuel cost with the slightly better efficiency of the new motor on a typical recreational boat! You're already getting pretty decent mpg, which just stretches out the payback period even further! It's the same basic issue as trying to decide between gas or diesel, with 2-3X more cost for a ~20-50% efficiency improvement, on a new bigger boat! I went through the same thought process when I was contemplating a repower on my boat, trying to decide if I should replace a reliable, good running 31 year old 2-stroke with a new motor that would cost over twice as much as I paid for the original rig! (albeit in MUCH LARGER 1975 size dollars!) The bottom line is, unless you use the boat nearly every day for something like dive charters or commercial fishing, the fuel savings is insignificant!

There's a more important and difficult cost/benefit analysis that nobody on the forum can do for you: i.e., is the benefit of (fill in the blank here . . . less noise & smoke, smoother idle, more power, improved reliability and parts availability, etc.) worth all that cash and extra weight?! (Even the new DI 2-strokes are a lot heavier than the old ones!) In my own situation, I had run the old motor for so long that I was simply tired of all the noise and smoke and premixed fuel hassle that I was ready for some newer technology! Also the ethanol issue can be a problem for the older fuel systems not designed for it. However I also did some boat shopping to see what sort of boat I could end up with for equivalent $. (the cost of a new motor & bracket added to what I thought I could get for my current boat.) I found that I could get something BIGGER and maybe a little newer, but I concluded that NOTHING (with the possible exception of a repowered Moesly 21!) could match the unique combination of seaworthiness, trailerability, and cruising amenities of a 20' Seafari with a new motor and a bracket! The old motor also had an aftermarket power trim system that had died, for which parts were no longer available. And despite good compression, with over 1000 hrs on it, cold starts required use of starting fluid, and I suspect it needed new reed valves, which was a lot of $ to put into such an old motor. Basic reliability was not an issue, because I knew that old motor so well I could tell whenever it needed attention and it was so easy to work on that it never left me stranded; I could always get it going whenever I did have a problem. Although the new motors are very reliable and run great, they're not nearly so simple and easy to work on!

As for question No. 2, the issue of NEW 4 strokes vs. DI 2-strokes, that's a question that has been and will continue to be debated on this and other forums ad infinitum! The performance and reliability differences are quite small and, with the E-Tec's, there is no significant noise difference either. I personally think the excess weight of the 4-strokes is a potential problem for the 18-20' hulls, especially with a bracket, since, unlike modern boats, they weren't designed for nearly that much weight. That's not so much of an issue on the 23's, which were often fitted with twin O/B's that were almost as heavy as the modern big single O/B's. Good luck with a tough decision (and convincing the wife!) I'm afraid I may not have been much help! Denny