At 08:27 PM 16/01/98 EST, you wrote:
>Bill
>Its DULEY  not DUDLEY

Sorry. Thought it was a typo. (very red face)

>All the original post said was Hall effect sensor.  I have used the
Interupter
>type hall sensors.  They are very expensive!

Not Hall effect. I am suggesting what nobody seems to have considered for
that diesel boat engine and that is an INDUCTIVE (reluctor) type. Been used
since the '60s on European vehicles. Got to be some cheapies at wreckers or
from after market auto suppliers. The nice things about them are 1) they
work in horrible filth, 2) don't need the tight clearances of Hall sensors,
3) no power required (2 wires) and 4) they're built to last. On this one,
you really can "Roll Your Own" if you want to. I wouldn't.

Bill

BTW. I've read the specs on sorta similar units from RS & Farnells and they
are deffinitely not in the same class. Low sensitivity, expensive & fragile.