87 force 125 hp low speed knock

[new outboard guy]

i have developed a low speed knock, kinda wierd. it stops when i go above 1500 rpm. runs ok, idles at about 750-800 rpm, no bad sputter or stalling, just a wierd knock. im thinking it may be the 2 cycle oil i put in, i had to go with crappy oil. i just wanna cover my bases and make sure i dont need to do more than clean the carbs and change gas and oil.

 

[new outboard guy]

Re: 87 force 125 hp low speed knock

ok i found it only starts to knock after a while of running, so im thinking it may be due to overheating. please help......any reply is appreciated.

 

[jason32038]

Re: 87 force 125 hp low speed knock

Sounds like my 85hp did right before the side of the piston went missing. Looked like the rings caught and broke a nice piece off. Take the head off and visually check the pistons and move them side to side. I'm sure if they're pretty loose like mine were then you'll need to overbore or hone and get new pistons and rings. You might need to go .010 or .020 over before it's too late.

 

[jerryjerry05]

Re: 87 force 125 hp low speed knock

Adjust the air screw.Bottom out the screw and turn out 1 and 1/16-1/8th.
Then do a compression/spark test.Check the timing.J

 

[new outboard guy]

Re: 87 force 125 hp low speed knock

ok found a few issues on the flywheel and trigger advancement. had a broker plastic clip on my timing advancement. fabbed one at work out of stainless and retimed perfect. now i have a woodruff key on the flywheel that is worn out. i cant seem to find it anywhere. a part number would be helpful for this. motor is a 87 125 type a motor. please if you have a number or anywhere i can get this let me know.

 

[further]

Re: 87 force 125 hp low speed knock

#16 in the diagram.

http://www.crowleymarine.com/mercury-outboard/parts/1233_8.cfm

 

[new outboard guy]

Re: 87 force 125 hp low speed knock

ok i changed everything mentioned above, and still have a knock once the motor is hot. im thinking maybe im not cooling the engine good enough, and that i may have sucked some water foliage into the cooling system. any more advice???

 

[MostlyHrmlss]

Re: 87 force 125 hp low speed knock

A quick easy check for cooling is to put your hand on the head when it's hot. If you can keep it there without screaming for two seconds, your cooling is fine, or you have nerve damage. If you leave skin, it's too hot.

 

[jason32038]

Re: 87 force 125 hp low speed knock

Retard the timing to 28 degrees dynamic. I hear it's reccomended for force motors.