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Well finally got the heads removed...Man I flush this thing every time I come back and still a lot of corrsion in them. The flow deflectors in the water jackets had gone completely south .....One was even getting close to shutting off the flow alltogether, They had deformed and swelled up to almost twice the normal size.
I decided to have the heads resurfaced at the local Machine shop, and while there at it remove the broken bolts.( Just couldnt bring myself to do it:D ) Hopefully they will be ready before the weekend.
Now I have noticed some carbon build up on the piston heads, nothing too bad but there is some.
Question is........should I go ahead and try to remove as much as I can or just leave them alone and run some decarbon stuff after I get them back together.
I am not really sure what to use that will do the best job of removing the build up. Anyone have any suggestions? I had thought about using a scraper to take it off but I sure dont want to do any damage to the piston or have some of the carbon get in between the cylinder wall and piston.
Anyway I think this is what the main problem was in the over heat situation. Feel pretty good about finding this gunk in the jackets as to the cause of the heat problems.

Now when I go to reassemble the heads....do you use any type of gasket sealer? I didnt see anything on the ones I removed and wasnt sure if its not to be used or the last time it was worked on if the mechanic he didnt use any.

Oh well onward and upward. Part 3 to follow.
 

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POC chunker
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The best thing going to decarbon is a product called "SeaFoam" from NAPA. There is a spray version called "DEEP CREAP". Run the motor at fast idle with the muffs on and the front of the airbox off the carbs. Spray the deep creap into the carbs until it is about 1/2 gone. The motor will smoke a lot. Let the motor cool down for about 30 minutes, then remove the spark plugs. Tilt the motor up as high as it will go. Put the straw from the spray can in each plug hole, and move it around while spraying to get the top of each piston. Spray the edges of the cylinder good so it flows down on the rings. Now, turn the motor over by hand about 5 revolutions to work it in good around the rings and cylinders. Put the plugs back in loosely by hand and let it set over night (or at least 3 hrs) for the solvent to soften the carbon.

Remove the spark plugs, and turn the motor over with the starter to blow any remaining liquid out of the cylinders. Put the spark plugs in and torque them down to spec. Then either launch the boat, or put it back on the muffs and start it up. The motor will want to rev high, so be prepared to turn off the key quick until the excess residue burns off. It will smoke a LOT!. It may take several tries of starting/turning it off until the motor will idle at normal speed. Then let it idle on fast idle for about 5 minutes until the smoke starts to clear up as the excess carbon and liquid burns off.
Launch the boat, and keep it under 3000 rpm for about 15 minutes to allow it to warm up, and let the rings reseat if they had been stuck with carbon before. Then run as usual. To keep it clean, run a can of Seafoam in a tank of gas every couple of months.
 

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You can also do a shock treatment of yamaha ring free. I do a simaliar treatment to what pocketfish said. I use mercury power tune, but only into the carbs not directly into the cylinders
 
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