1984 Froce 125Hp breaking woodruff keys

[stevbov]

Hi,

I fairly new to boats, not much of them in Ireland. We have one with a Force 125Hp which keeps breaking woodruff keys over a short period of time. I have noticed a knock from the engine when we take it out of gear so assuming that it's due to this but cannot figure what could be causing the bang. The engine sounds and runs great when it's running but after 3-4 trips out it won't start, not even attempt. Any ideas on what I can check.

Thanks Stephen.

 

[Jiggz]

Re: 1984 Froce 125Hp breaking woodruff keys

Knocking can be due to pre-ignition or detonation. If the knocking only occurs after the engine has run for awhile and the engine runs hot (above 180F or 82C) it could be detonation caused by lean idle fuel and malfunctioning thermostat. Correct this by setting the idel mixture screw at 1 1/8 out from light seated.

However, if the knocking is present even when the engine is not hot, it could be pre-ignition caused mostly by high carbon build up in the piston head and cylinder head. De-carbon the engine by running at idle and revving it up while shooting straight sea foam into each of the carbs. You should see carbon dust exiting the exhaust if there is high carbon build up. Do this until the exhaust is clear of carbon dust or has become minimal. Usually this takes no more than 10 minutes to complete. Remember only shoot (using spray bottle) when you are revving the engine. Too much will kill the engine so start by shooting a little and increasing while the engine increasing rpm. After de-carboning check plugs to make sure they are clean.

After replacing the woodruff key make sure you torque the flywheel nut to 125 ft-#.

 

[Frank Acampora]

Re: 1984 Froce 125Hp breaking woodruff keys

If you keep breaking keys and you have torqued the flywheel nut to 95 foot pounds (Clymers) or 90 foot pounds,(12.5 KG/M Factory Manual), then it is time to re-seat the taper on the crank nose and flywheel. with the flywheel off and key removed, apply lapping compound to the taper. Set the flywheel on and rock back and forth a couple of times. Rotate 90 degrees and rock again. Do this until you have completed the circle. Now clean everything and test for mating. Scribe a number of vertical pencil lines on the crank taper, replace the flywheel and spin it. You want about 85% or more of the lines rubbed off.

 

[jerryjerry05]

Re: 1984 Froce 125Hp breaking woodruff keys

Check the timing too?

 

[stevbov]

Re: 1984 Froce 125Hp breaking woodruff keys

Thanks for the answers, I'll give it a try when I get the new woodruff key. To honest I haven't been torquing the nut, just making sure it was well tightened down :redface: so hopefully when I do it correctly it will work great.
Jiggz, the knock or clunk is only when we take it out of gear, it happens all the time doesn't matter if the engine is warm or cold but only when we go from forward/reverse to neutral, when we're in gear the engine sounds good no unusual noise.

Again thanks for all the help.

 

[Georgesalmon]

Re: 1984 Froce 125Hp breaking woodruff keys

You might wanna do as Frank suggested before you run it again. Because your flywheel has "spun" a few times it likely does not have a smooth surface anymore. No matter how much you torque the nut it will never hold until the mating surfaces are perfect. What Frank is telling you to do is cheap and easy. Oh, yeah,,,,,Been there done that, it works

 

[foodfisher]

Re: 1984 Froce 125Hp breaking woodruff keys

Your idle speed may be too high.

 

[Jiggz]

Re: 1984 Froce 125Hp breaking woodruff keys

Your idle speed may be too high.

This will be the first thing I will check. In fact, this is very destructive to the clutch dogs if you continue to experience a "thug" or "clunk" whenever you shift gear. Idle rpm in neutral should be around 1000~1100 RPM and in gear should be around 700~800 RPM. Anything higher will "jerk" the LU and anything lower can stall the engine when you shift gear. You might also want to check the remote cable is properly adjusted that it sets the engine throttle back to idle first before shifting to neutral. You can check this by shifting to F or R and then raise the RPM to about 2500 RPM go back to idle (still in F or R gear) and the rpm should go back down to around 700~800 RPM, pretty quickly since it's loaded. If it doesn't you need to adjust the remote cable to make sure it returns the throttle to idle setting before it shifts back to neutral.