We have 3208TA at 435 in our 50 ft 40,000 lb plus flybridge boat and have been very happy with them. We have put 700 hours in 3 years with no problems (total 1400 hours). One thing in particular I like is that they are mechanically injected and have a much simpler and reliable engine control system. Their HP per liter and HP per pound is much less than many of the newer high reving or higher HP turbo diesels.
I would think that in a 37 ft Tiara these would work very well and you could cruise at 20 knts plus and run the engines at 60% or less of WOT fuel burn. In our boat we cruise at 20 knts and the engines are at 60-65% WOT loaded. These are also very fuel efficient at cruise. Of course the hull design counts, but we burn 28 to 30 GPH at cruise.
I think the reliability problems were the result of two things. First, you must keep up on the seawater coolant system. And the aftercoolers need to be inspected every three or four years depending on use and age and replaced if needed. These I think were a problem and some failures were the result of the aftercooler and a metal mismatch in the connector pipe that was addressed, although several manufacturers have had aftercooler problems over the years. The other contributor I think is that some installations were in too heavy of boats (over propped)and these owners ran their motors way too hard and if the cooling systems started to clog, then big trouble could occur. Newer boats tend to have bigger engines relatively speaking, but they are also more expensive several ways.
There are many 3208s out there and good CAT service and reasonable parts pricing are readily available.
To get an engine survey, I would call Pantropic in Ft Lauderdale and get a full instrumented engine survey. It is not cheap, but money well spent. I did this and you get complete engine and cooling system performance numbers,
