Most decent installations of larger diesels have mechanical oil pressure and
temperature gages mounted on or near the engine. This way you can check you
engines for the things you are concerned about. For the Tachs, there are
handheld instruments that work in various ways to check with.
If you have a converted car gas engine then you can install these for a few
bucks.

--
Ron White
Boat building web address is
www.concentric.net/~knotreel