Johnson "70mod"

[filthy phill]

here is a couple of pics to show what OMC done to inside the exhaust cover to improve the cooling of the no 1 and 2 cylinders.
the small hole at the top lets plenty of water get to the top two culinders and any air expelled out the top tell tale fitting on the top of the block.
this simple mod made a lot of difference.
along with changing the timing to 17 deg instead of 19.. seems 19 made it run too hot ? also larger main jets were put in the carbs to stop the motors leaning
out and destroying the pistons and sleeves.

anyway, here is what OMC done to make the later oval port run the best for cooling.