Piston Pitting 25 HP 1977 Evinrude

My 1977 25 HP manual start Evinrude has a deep pit in both piston faces. I discovered this while trying to determine if my engine died at idle because of lack of fuel or flooding. There is one pit at about 10 o clock on both pistons when viewed thru the plug hole. They are about 3/16 bi 1/16+ deep. Top 1 is bright-bottom is carboned.

History: The engine has not started or run at idle well for a short time then it just refused to start. I soon found there was no spark. After testing all I could I installed a new Power Pack and it started but immediately died. It then was extremely hard to start again. I have cleaned the carb 3 times to include high pressure H2O and probing with soft wire. All passages seemed clear to include fuel holes in top of carb throat. New bowl and H. speed nozzle gaskets were installed as well as S. speed needle packing [new style]. Float set at parallel to carb base. Slow speed needle set 1 1/2 T out. I also tried at 3 full turns out w/ no change. New fuel lines and bulb and F. Pump screen. Gas line disconnected at carb and rope pulled pulses gas out. New bulb delivers gas well and the gas tank is clean. There is no leakage at the fittings. I installed 2 new Champion L77JCH plugs gapped at 30 T. New non ethanol gas at 50:1 in a clean tank.

When I took the slow speed needle out I noticed about 20% of the packing was missing. There were 3 pieces still in the threaded portion of the Carb despite having removed the needle !!!!I washed this out by inserting the straw of a can of carb cleaner past the debris to insure I didn't force it deeper. I probed the idle holes in the top of the Carb throat as well as the slow speed tube extending upward from the bowl. Carb cleaner seemed to pass these areas well after that.

Compression is 98 and 100 psi. I believe the T stat works properly as the engine warmed quickly on muffs and yet I could hold my hand on the top of the head and crank case w/ slight discomfort. I had to run at more than a fast idle to keep it running. It emitted a lot of white smoke which I assume included steam as it was in the 50 degree range.

The plugs show no evidence of touching the piston and the pits are not centered where I assume the gap would be. What is I my problem??? Bill

Some pistons have a " deep pit " in them.---This was from a machining centre from the factory.------Without a picture I can not tell if that is what you are looking at.--Was the high speed jet removed and cleaned ?----It is screwed horizontally into the carburetor bowl.

Racerone.
I did not remove the high speed orifice but did clean it well and it seems clear. Another thought came to me and that is I had to open the throttle by hand (not using the tiller) thus the cam did not move and the timing would not increase. Could this cause a problem?
Also, if part of the packing was forced past the low speed needle into the chamber above the holes in the top of the carb throat I assume too little gas would get to the cylinders. I assume the welsh plug would have to be removed for inspection. Hope this helps in your analysis. You guys are great. THANKS VERY MUCH Bill

Racerone.. I do not believe the pits are machine marks. The top one is VERY BRIGHT AND SHINY. Also there are a few speckled bright spots below and to the right of the pit. The bottom one is carboned over a bit. I did not notice the pits a day earlier but I may not have bent down low enough to see them as I did later when I used a flashlight as it was getting dark. Hope this helps. Bill

detonation could cause pitting....that is usually one of two things in a 2 cycle...not enough fuel in the fuel air mixture or timing..

Papyson.. Thanks for input. Compression is about 98 psi both cylinders. It is my understanding this engine has no way to time except carb to cam. That is off a little whereas it was right prior to this problem. I have tried to take photos of "pit" last night and today in daylight-NO GO. I am going to pull the carb again as I am fairly sure the idle passage has debris even though it seems open.

Kim. Am getting parts to finish carb rebuild.
Head was trued w/ new gasket installed 2 years ago with very little use since and no heat/ water problems. Also replaced H2O impeller then and now even though it was pumping fairly well - just was given a new impeller not used by a friend so I installed it. Both cylinders are 97 to 100 PSI. Thanks for input. Bill.

PS See my response to Kim.

Kim @ racerone. I've been laid up w/ hand surgery but finally pulled the head. The pits in the pistons are from machining. Rebuilt the carb, new power pack and engine popped right off.then the next day no start and no spark-next da same scenario. Thinking this a new problem I started new thread entitled "1977 25 HP Intermittant (sp) spark" dated 4-19-2014. could you give me your thoughts? I cant believe both PP are bad unless there is something about my motor causing it, in fact I wonder if the original PP was bad. I really would like your thoughts even though my question may be stupid. Thanks Bill VV