1987 70HP JOHNSON

[apierce]

Hi, I recently registered on this forum because of the helpful hints I was getting for my boat. Now I am here to seek help that I did not expect to need so soon. I recently purchased a 70hp ob that was running great on the trailer at idle and with the controls and earmuffs on. Once I put the motor in the water to take it for a spin on a 19ft ski boat it was all downhill from there. I originally was putting the engine in to see how the boat and motor ran together, now I have bigger problems. At first the motor would only go about 5-10mph and when I gave it any gas or a higher throttle with the controls it would stall. This went on for about an hour. The motor would run at full speed on the trailer with earmuffs or just out of the water but once I put it back in it was stalling at low speeds. Next I was cruising around at the slow speed and for some reason it just kicked in and I was off and running at 25-30mph for about 5minutes. THEN THE MOTOR SIEZED. I originally thought that this was electrical but that was not it. The Fly wheel on the top of the motor does not budge. BARELY MOVES WITH BOTH HANDS ONE TICK AT A TIME. I took it to a marina locally and after they removed the lower unit to check for any problems there, they told me the motor must have internal damage. Crankshaft ?? The plugs looked fine and there was no evidence of overheating ? No caking or water ?? Also no smoke when it JUST STOPPED ? Any suggestions on how I may free up the Flywheel would be greatly appreciated ? A manual would be very helpfull too. I feel that the marina did not want me to spend big $$ on an old motor but I feel that this motor was running great all winter and just as it got into the water something bound or happened to the Crankshaft. Is this something I can repair ? I have another spare 87 Evinrude I can use for parts if this Johnson can be fixed. ANY CLUES ? andrew.h.pierce@verizon.com

[petryshyn]

best pull the heads and have a look. Sounds like you had a lean condition which resulted in overheat and seizure. The cylinder walls and pistons will tell the tale.