25 HP Johnson seahorse knocking real bad

" I have a 25 HP Johnson seaho

" I have a 25 HP Johnson seahorse (not sure exactly what year it is, probably around 1980) that started knocking really bad out of nowhere when I was just trolling along a couple days ago. It really gets bad at higher RPMS but it only does it in forward gear and there is no loss of power at all. I would think if it were a rod, it would have froze up by now. I took it out and ran it again just the other day for approx. 3.0 miles and it still kept running good but sounds just terrible. When I had it out of the water I tried putting it in forward gear w/ the engine off and the prop turns the cylinders fine and I couldn't hear any problem in the lower unit and the lower unit gear lube level is fine. Any ideas? Jeff "

"Jeff... To check possible pis

"Jeff... To check possible piston, connecting rod, and/or crankshaft problems. Do the following.

(Piston Play Check)

This procedure will tell you if there is any wear or play in the Wrist Pin, Wrist Pin Bearing, or Connecting Rod to Crankshaft area.

Remove the spark plugs. Insert a screwdriver, dowel, punch, or some object of your choice through the s/plug hole and into the cylinder/piston area. Hold the tool lightly against the top of the piston.

Turn the flywheel by hand, bringing the piston up to top dead center, then continue turning the flywheel to pull the piston down about a inch..... all the while holding the tool lightly against the piston top.

Now, at the point whereas the piston has been dropped down about a inch, grab the flywheel and hold it firmly. Now, push that tool solidly and firmly against the piston top. If the piston moves downward without moving the flywheel, there is a problem (wear, play, clearance, etc) somewhere with the items mention in the first sentence. Be sure to check all of the pistons/cylinders.

Joe "