View Full Version : 1983 40hp merc lockrelease cam

02-20-2008, 11:06 AM
"JB, i have sorted out the gearbox probs and all is changing fine, took it out for a spin and she went good a few more adjustments in the timing to get her up on the plane a bit quicker and i should be set.. Although i did notice when in reverse the cam is not locking the motor down and i can lift it up. i tried adjusting the cam around one tooth on the spline and it locks down in reverse but also in neutral, it only becomes unlocked in Forwards. By the manual and the digrams i have it set right but the spline seems to be about 1/8th to 1/16th out of correct alignment to the travel on the cam. when the reverse gear is selected there isnt enough turn on the spline for it to engage the lock mechanism. i have checked travel on cable and adjusted both ways from original setting to see if it makes any changes but to no avail, same problem. the shift cam is in good order and the lifting lever and hooks push up freely and are well lubricated. Yet again the Merc had me stumped."

02-20-2008, 11:23 AM
"locking down in neutral is correct by the book. This would plant the boat/motor on the shore after use. To lift engine, put it in gear. Mine is set so it only locks in rev, this can cause it to not lock under hard reverse, some what embarrassing at the boat launch when motor jumps out of water. It must release in fwd in case you hit something.
Do not mess with timing, set it and forget it. Change prop pitch/diameter for the right set-up. 10 1/4 x 13 or 10 3/4 x 12 work for me. To much pitch will destroy engine."

02-20-2008, 11:34 AM
"Where would i be without your help JB Ive been reading the manual which mind you gives no indication that the engine locks down in neutral, and ive been scratching my head in utter confusion over this till ive nearly worn another hole in it and then, hey presto JB has the answer.
The timing was put a bit out of wack when the top end was all apart when I re did the midsection and powerhead gaskets to stop the water entering the bottom cylinder. I have again looked at the manual but am still not clear on where the timing advance lever should be sitting at idle and which position on the stator it should be at WOT. It isnt all the way to the front of the stator at idle but its about 1/5th of the total distance towards the back of the engine, and when at WOT its about 4/5ths all the way to the back of the engine in its travel. Is this way off where it should be?"

02-20-2008, 12:46 PM
"1/5 to 5/100000, who cares, at idle the timing is 3-5 degrees, at full power 27 degrees or slightly less. when you put it in gear the carb pick-up should be just a hair away the carb cam, this keeps the engine from jumping when you shift it in fwd. When at full throttle the linkage should hit the stop before the carb butterfly hits the internal stop of the carb. Check your email in a moment."