1408430 78 140 Rude

"Hi Folks, Wondering if anyone

"Hi Folks, Wondering if anyone can give me some advice. Not sure if its a motor, or boat issue. I have an old 17 1/2 foot cruise craft half cabin. on the back is my old 140 hp which works a treat. When cruising around @ 6 knots, engine sounds like appropriate revs for the speed, (ie revs dont sound excessive for speed) , when gunning it and planing, engine sounds fine for speed, (ie revs dont sound excessive for speed).
But it seems when try cruising in that middle area, between 7-12 or so knots, but not planing, the revs sound excessivly high, or the motor seems to be working harder then what it should for the speed being attained.
no tach, (basing on ear) no speedo based on speed of another boat. Is this common for an older motor ?, prop issue ? any ideas ? Thanks in advance .... Dave"

If you Think it's like a c

If you Think it's like a car and RPM match road speed sorry It's not.

The motor has to work very hard at fast non planing speeds.

The jump from non planing to planing needs very little extra power.
That is why it is heavy on gas at fast non planing speeds.

"Cheers Jack, Gottcha !, Im st

"Cheers Jack, Gottcha !, Im starting to realise these things are nothing like cars.... or Motor mowers, as they have been prev discribed by a friend."