How do I set timing on a 1985 mercury 75hp

[maxum00722]

After a stator change my motor was hard to start. When i put it in the water the engine would idle in neutral and in gear but as soon as i push the throttle forward it kills. I rechecked the stator, checked the trigger and cleaned the carbs. I was told it might be a timing issue. Can anyone tell me how to set the timing? 1985 mercury 75HP 4 cyl. Thanks

 

[CharlieB]

Re: How do I set timing on a 1985 mercury 75hp

First, check here to see if your service manual is still availbale

http://forums.iboats.com/showthread.php?t=309079&p=2072211#post2072211

Next, with the engine OFF, disconnect the throttle cable and push the throttle to WOT while watching the timing lever to ensure it has full travel and is not sticking or binding anywhere.

When you cleaned your carbs, how did you adjust the idle mixture and float height. A common error is to adjust the idle mixture too lean. 2 strokes need an excessively rich idle mixture for acceleration, idle mix is set to best idle IN gear while IN the water and IN Forward gear PLUS almost another 1/8 turn out (CCW). Much less and the motor can die. lean cough, sneeze, bog, etc.

Max timing can be set cranking, IN gear at WOT. Remove all spark plugs and ground all the plug wires, REMOVE the prop to protect your leg from serious injury. If you don't like spark bite, do this on the trailer, and even then it can get you.

Specific # should be verified with your service manual, it should be in the rage of 21 to 23 degrees, (IF my faulty memory is correct).

 

[maxum00722]

Re: How do I set timing on a 1985 mercury 75hp

Thanks captain I have not checked the timing yet, but on a dfferent note, could my problem possibly be a bad fuel pump?

 

[CharlieB]

Re: How do I set timing on a 1985 mercury 75hp

Definitely, pull the fuel line off at the carb, crank the motor with the lanyard pull so it won't start, you just want to see the fuel flow, it should be a strong pulsed flow at least an inch and a half and the diameter of the hose.

If you suspect an air leak sucking into the line anywhere before the pump, temporarily install a clear hose to the carb and watch for bubbles while running the motor. Remember to remove the NON-rated clear hose once finished with repairs.

 

[maxum00722]

Re: How do I set timing on a 1985 mercury 75hp

Thanks agiain for your help

 

[hempfarmer]

Re: How do I set timing on a 1985 mercury 75hp

When you change the stator or the switchboxes is it crucial that you adjust the timing? Or is generally okay?

 

[CharlieB]

Re: How do I set timing on a 1985 mercury 75hp

If you haven't changed the trigger linkage the timing should remain very close to perfect, IF, it was perfect to begin with.

Follow the directions to set WOT timing while cranking. All spark plugs removed, all plug wires grounded, remove the prop, shift into Forward, WOT, crank with a remote starter button and see where the timing light shows the mark.