Johnson 25hp woodruff key problem.

[the Novice]

Hi all I have a long running problem with my 25hp Johnson. I changed the woodruff key to the flywheel about 6 weeks ago ( for the second time in a matter of weeks), it was tightened down to the correct tension yet it has sheared again after about 12 hours running time. It sheared on starting, and when I undid the flywheel nut it was ( or at least it seemed ) looser than when tightened. Is this possible? and if so would it be wise to use lock tight on the nut? Or is it possible to give the engine too much throttle on starting? As it only seems to go when starting from cold.
Thanks all.

 

[tashasdaddy]

Re: Johnson 25hp woodruff key problem.

are you using the oem part for the key? hardware store keys will not last.

 

[F_R]

Re: Johnson 25hp woodruff key problem.

Every time the key shears, it damages the crankshaft and flywheel a little bit more. It could be too late. A close examination is due. The parts have to be perfect.

The crank and flywheel tapers must be clean and dry before assembling, and the nut torqued to specs.

NO LOCTITE!!!

 

[the Novice]

Re: Johnson 25hp woodruff key problem.

hi I am using oem parts only, and as this is an ongoing prob I know straight away what has happened and do not try to turn the engine, so there is no visible damage to either part.

 

[seahorse5]

Re: Johnson 25hp woodruff key problem.

The old timers fix for that was to use a bit of valve lapping compound between the crank taper and the flywheel, with the key removed. Work it gently until you see an even pattern on the crank and flywheel bore. Clean everything thoroughly, make sure a new key fits snugly in the groove, then torque it to the required spec. Use laquer thinner or something strong to make sure there is no oil or grease on the tapers.

 

[Texasmark]

Re: Johnson 25hp woodruff key problem.

10-4 on having to be perfect. I am amazed at the difference in timing/running/ability to start it, of an engine with just a couple of degrees of slip/damage to the woodruff key.

Mark

 

[Dhadley]

Re: Johnson 25hp woodruff key problem.

One thing to look at is the bottom of the flywheel nut. It has to be flat and smooth. If there is a burr on the bottom, you're tightening the nut on that burr not the whole surface and it'll come loose pretty easy. Seen it several times.

Remember, the key doesn't hold it in place. The key simply lines the flywheel up. The interference fit between the 2 tapers is what holds it. And the nut is what keeps the pressure on the 2 tapers.

 

[ezeke]

Re: Johnson 25hp woodruff key problem.

What torque setting are you using?