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Re: Anyone know the comp ratio for 81 merc 70hp 3 cyl?
This question came up is service school years ago and was told that the early high dome pistons was around 14:1 ratio and the low dome was 12:1. That the reason the early 1400's and 1500's had around 145 psi compression.
Re: Anyone know the comp ratio for 81 merc 70hp 3 cyl?
Given all of the variables (besides actual compression) that can affect the readings the best you can ask for is over 100psi and all cylinders within 10% of each other.
Re: Anyone know the comp ratio for 81 merc 70hp 3 cyl?
My Merc service manual for loop charged engines which only have 2 variable compression rings instead of 3 like the cross flow had says as JB said, could be anywhere and what matters is that they are close together in their readings......course your accuracy in getting your readings is important too. It goes on to say that if the numbers are 120 or lower you can expect to have service soon.
