not making speed

[gettinthere]

I don't seem to be getting the speed under power I used to.
Cleaned the prop & bottom, that wasn't it.
I still reach the rpms normally, engine isn't overheating, maxprop seems to be folding properly; but I'm at least a knot slower, more like 2.

 

[kloudie1]

Is the paddle wheel for the instrument fouled? Speed measured by GPS?

 

[gettinthere]

Speed measured by gps, over several trips, some certainly at slack tide

 

[Bill Roosa]

perhaps the max prop is not fully turning to the set pitch resulting in under proping???

 

[geehaw]

Prop bent, if outboard tilt changed, key sheared prop still turning but slipping on shaft. Greg

 

[geehaw]

Oh more weight in boat? Eat to much this winter? Joking.

 

[kloudie1]

tachometer reading verified with a hand-held?
following Bill, has anyone done work on the prop and possibly changed the pitch setting?

 

[Benny17441]

Is the time interval recent? A loss of compression can result in reduced HP. When was the valves lash last adjusted? Thin oil can account for reduced compression on a 25+ year old engine. How is the transmission working? Is the fuel in good condition? Is the alternator energizing more frequently? It's hard to diagnose through the net but just giving some ideas that may account for reduced performance from the engine.

 

[Dantodd]

Rpm/speed should be constant. I would suspect either the max prop is not working properly (mis-adjusted or opening stops failed) or maybe the shaft coupling is slipping.

If the engine is still putting out the same RPM that means the prop should be moving the same speed. If it the prop is turning the same speed then something has changed with the pitch. If he prop isn't turning as fast as before it must be the transmission, the coupling, or the prop/shaft connection .