That really applies when the diesel is turbo charged and run under heavy
loads for long periods of time . Back pressure is what keeps the exhaust
valves from burning .Your situation poses no problem.I am diesel mech. for
Mercedes.

Sal


"John Knox" wrote in message
...

i have read of the importance of insuring that
manufactures specs on back pressure are not
exceeded, but i can find no numbers for my
yanmar 2gm15. does 48" from bottom of water
lift to top of transom gooseneck using 1.5" hose
sound excessive?
john