"I know I have been asking man
"I know I have been asking many more questions than answers here, but this subject is something I had put some time into before the current failure on my 454 single as I was looking to upgrade etc.
First off though I understand the difference and issue some bring up with the 4.3 v/s 350 type small blocks I have to agree with the others that the 4.3 is a solid base to work with, and add that the issues I have heard of were of extreme conditions like racing, or poor maint etc.
I have actually owned a few vehicles with the 4.3 engine, and personally have not had a problem with any of them (well besides the old BS GM throttle body injectors lol) so to me the engine shouldnt be a problem if fitted properly to the boat, and your way of running.
That said I believe the more important things to look at (besides what has been stated earlier) are how you really use your boats, and how the boat and power pair up.
I know the boat mfg's have changed how they measure, and build boats etc, and an old 28ft can be both heavier and even larger than a newer 30ft or more.
This really effects engine choice, and if you prefer or demand a boat that can get up and go like I do it is something that not only will effect engine life, but also your enjoyment of the overall package.
As I will use well known name as an example so that most can follow my thinking etc. Searay had offered two models the sundancer and weekender in the eighties and ninties that changed greatly (actually night and day) in design, size, and weight, and therfore power needs as well.
The old 30's had a wider beem, more weight, and normally had a min of twin 350's, but the newer 30's of the 90's were barely 30' overall, were thinner, lighter, and demanded a lot less from a similar power package.
I have even seen some of the older ones with the 454's and even some of the old 27's (like todays 29-30') with twin four cyl, and they all get you from point a to b, but also very differently.
Lastly I found that different hull designs perform better or worse with smaller power packages. Some inboards ride with a much higher bow when underpowered (or even just run too slow) while the same hull with larger engines, and even i/o's will run like crazy.
Of course if your pushing an under powered boat hard its going to burn a lot of fuel, and reduce engine life (when compared to a similar maintained engine used at lower rpms).
So be sure to put some time into learning how each model your considering performs with each power package, and dont be afraid of the v/6's if they are properly matched to the boat, and your way of running, but try and be sure the boat and power match your needs so that you get more enjoyment per $$$.
PS here is a great link on checking out a used boat. I have done some fiberglass work in the past, and found this guys info impressive (most dont share this stuff lol).
Good luck
http://www.customboatrepairs.com/tips.html"