Originally Posted by Mark I
I believe they were all built on the same basic block. Maye someone else will chime in with more information but I don't know of a TID. A good engine survey is a must regardless. There is scheduled maintenance on 500 hour intervals in addition to the annual tasks so look to see the records. When you start getting into turbos, injectors, rack adjustments etc. this can run into a little bit of money.
As far as the boat is concerned, I think the production run was from 1983 to 1989 or early 1990. There were small differences in appearance and amenities but the hull was the same.
A friend of mine had a 1987 41' with 8v92's, at 1800rpm's it only cruised at 21 knots. You could cruise it at 1950rpms if you'd like. I ran another 41' with 6v71 naturals and it cruised at 14 knots at 1950. So 6v71 turbo's should cruise close to the 8v92's in speed. I have no familiararity of the 38'.
6-71 TIB's are good engines for Detroits and as far as I've seen last longer then the TI's. The B stands for bypass, DD installed a bypass valve which helps the turbo's last a little longer by bypassing some of the un-used boost.
Having a tune-up done on detroits should cost you no more then 3hrs labor per engine. They usually adjust the valves, set the rack, and injectors. Not a big deal. It 99% of the time never harms Detroits if it hasn't been done. You just might lose some HP and RPM's that's all. Turbo's should be inspected by the engine surveyor prior to buying the boat.