2004 Evinrude 250HP knocking/power loss

[littledutch]

I have a 2004 250hp Evinrude 2stroke, saltwater edition. Has over 600 hours on it. Was running about 4700-4800 RPM's with a full tank of gas, dive gear, four people, seas 2-3 occasional 4 footer. I was throttling with the waves up and down a bit to avoid hitting hard between waves. I felt the motor lose some power and I down throttled immediately and turn off the motor. Took the top off, turned the crank wheel by hand almost all the way around and it stopped short of a full rotation. The motor did not seize nor over heat. No alarms. Water pump working just fine. Did have some trouble getting it to start while at the ramp, had to throttle up a bit just to keep her from idling strange. Will say that earlier in the season, every time in reverse there was some knocking and some abnormal idling as well. There is no visual sign of anything broken, fuel injectors are not leaking, no oil spills anywhere. I started the motor once while in the water, cranked fine but knocking and was turned off immediately.
Any ideas on what may be wrong? Someone said I needed to replace the power head. Another said go get a new motor. Another said maybe a rebuild kit would do the trick.... need some help.

 

[joereeves]

You obviously have a major engine problem. First sign of knocking sould have been a clue to stop using the engine. To continue on.... it just gets worse.

Besides taking a compression check...............

(Piston Play Check)
(J. Reeves)

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 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.


Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

 

[littledutch]

Got the boat to an Evinrude mechanic a week ago. He started breaking down the block. First he removed the plugs and found cylinder #1 plug was smashed in. After breaking it down further and getting into the power head, found that the piston head in cylinder #1 had broken clean off from the arm. There was some heat galling on the piston. On a side note, two summers ago the oil system was having issues and would go into saftey mode. This happened several times and I was not sure exactly what was wrong. Two of those time we idled back to the ramp which was not far but could have caused the start of this damage. I have since replaced the entire oil system.