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1990 150 Went through all the steps from this forum to quiet the overheat alarm. Am now going to remove the heads and jackets to do a proper cleaning next month. When going through the troubleshooting steps, I delt with a stubbon bolt on the termstat housing and had to do the "remove broke bolt sequence". Corrosion under the cowling is present but not bad. I did a check on the 5mm jacket bolts and some loosened easy and a few seem "unwilling". Seems like I should remove the heads first? Any advice from the experienced folks on this fourum on what to expect and the proceedure when removing the heads / jackets will be greatly appreciated.
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19.6' Predator, 90(?) Yamaha 150 ETLD, Stock in every way, Water pressure Gauge, Runs great, Lots of PM, Salt water operation. Aircraft mechanic.. -
If you have unwilling M6 bolts in the jackets try putting the whole head in an oven. A little over 100 degrees Celcius will make it very much easier to undo the bolts but will not burn the paint. 250+ Celsius is enough for replacing a sleeve but that changes the colour of the paint. If you have a short torso of a bolt sticking out of the threaded hole weld a drop of steel onto the bolt (MAG). The heat of the welding will loosen the bolt a little and it is easier with right tools to grap that welded end. And heat up the whole head in this case also.
A vibrating pneumatic or electric tool is good if you can limit the torque right. Don't bend the bolts with the tools - turn them.
Let us know how it went. Good luck mate.
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