My son just bought a boat with a 89 70hp Johnson. If plugs are in it will not turn over the motor. We have installed a new starter and connected 2 batteries in series to make sure it is getting enough power. It turn over quickly with all plugs removed. If we install one plug or compression gauge, it will not turn over. Could there be something restricting the exhaust and building too much pressure? The previous owner said it had been sitting for 3-5 years.
Thank you
Thank you