A bit late to the discussion, but late in 2017 i repowered my 238 Vista with a Volvo Penta 240-C. I got a package and therefore brand new inboard and outdrive, along with clocks etc.
I bought my Vista very cheap a few years back and ended up spending more time fixing engine issues as i did using the thing; for me though i knew it would be worth the investment as all other things (Uphostery etc) i'd done myself. Once Engine installed my insurance valuation is still more than the boat + Engine Bill so i'm still the right side in terms of investment!!
Last year i did 100+ hours as the weather was amazing, this year i've done circa 50ish so i'm definitely getting the use. The reliability has also meant further trips afield and i no longer have to spend the time i'm driving listening out for funny engine noises nor scrolling through parts diagrams and ebay for spares!!
So what's it like? Well i boat in Jersey (UK) so salt water. The 240-C V6 is mostly Aluminium, so it's lighter than the old cast iron blocks, it has closed cooling inside the engine so antifreeze and heat exchanger, so that's good too. It gets up on the plane easy, and revs to 5600, i don't think i'm doing much faster than i did, well not a whole lot noticably anyway - but the engine is so much smoother than the old one i had and as i said always starts on the button every time.
The point about the exhausts is correct, it has catalytic converters for the emissions, also two oxygen sensors each side so replacement may well be quite pricey, i did price them up when i went for the package but can't remember 100% how much, they should last 5-7 years anyhow so fingers crossed that's a few years away!! Each exhaust has an anode inside that needs checking every year.
When i went for this package i priced up the mercruiser 250 also but it was more expensive and didn't have the closed cooling (From memory).
I'd definitely buy again, no complaints so far (Except the initial outlay!!) - only negative is the warranty is only 2yrs on everything, after this you're only covered for major components for 5yrs. In all fairness to VP though i had an oil leak from the propshaft last year and it was fixed under warranty with no bill.
It was a stretch to this but if i could have afforded the 280 V6 i probably would have got that. Overall though, i'm extremely happy with the package, it's transformed how much i use the boat
If you have any other questions just let me know.....