Fly Wheel Spinning

I'm just an old guy who wanted to do some fishin'. I recently purchased an old boat with a 1965 Johnson 40HP outboard motor (Model Number RKL-27-A). She hasn't been running very well and with the hood on it would be choking itself out - running very rough. Yesterday I had it tied to the dock and again had the same problem. Unfortunately the story gets worse.

I had the throttle about half open to just keep her running and decided to remove the hood. As I did the motor got enough fresh air that she immediately ran full open and then quit. Now, as I hit the ignition, everything engages - but the only thing that happens is the flywheel spins freely. There is no compression. I pulled the plugs and the pistons don't move.

I am thinking the connecting rod - but not being very mechanically inclined - I'm not sure. Any ideas?

I really can't throw a lot of money into this old boat but can't seen to find anyone in the area who will even look at it because of it's age. Is there a step-by-step manual or repair guide out there that may help?

Re: Fly Wheel Spinning

pull the flywheel it has a woodruff key. that engages the flywheel and the crankshaft. it probably sheared, and the previous owner probably did not torque the flywheel down properly. you have an exhaust leak from the leg bank into the engine compartment. it is breathing dirty air. low oxygen, thus when you open the cowl, it go good air and took off.

Re: Fly Wheel Spinning

Thanks - I am on my way out to try that as the woodruff key "had" broken and I replaced that last week. Hoping that will be it.... Being an old guy with limited funds - really can't spend a lot on this - but just want to fish....
You sound as though you have a lot of experience with this - so again THANK YOU! Here's To Hoping..............

Re: Fly Wheel Spinning

When you replaced it last week what did you torque it down to?

It should be around 100 foot lbs according to my manual. And that's a lotta torque.

Re: Fly Wheel Spinning

if not torqued it will shear again. the key is just to line up the flywheel, the torque is what holds it in place. flywheel and shaft have to be perfectly clean and oil free.

Re: Fly Wheel Spinning

Once you get that flywheel installed properly as tash said, the deal with running lousy with the hood on is another issue. There is an o-ring on top of the water pump housing and two more on the driveshaft housing tube extension if long shaft. If somebody leaves those o-rings out when repairing the water pump, smoke will enter the driveshaft tube and exit at the vent hole at the top, which is under the hood. Result is the motor is trying to run on its' own exhaust smoke instead of nice clean air. The smoke kills it. And it will drive a normal person insane trying to figure out what's wrong with it. There, I saved you from insanity.

Re: Fly Wheel Spinning

tashasdaddy said:

if not torqued it will shear again. the key is just to line up the flywheel, the torque is what holds it in place. flywheel and shaft have to be perfectly clean and oil free.

Click to expand...

If it's the torque that holds it down they should have designed a square shaft head or a D shaft like electric motors then. The steel key must hold it somewhat.

Re: Fly Wheel Spinning

Steve it is compression that the reason they are so hard to come off.

Re: Fly Wheel Spinning

TD is right plus the mating tapers ... kind of like the taper on a Jacobs chuck for a drill press w/o the key. BTW, the key is solely for locating, not holding anything. That's why the bore and taper MUST be dry and clean to hold.

Re: Fly Wheel Spinning

If you have ever removed one of those flywheels that was in good conditon and properly installed, you would know that they don't slip. Most people write in here asking how to get it unstuck. (Takes LOTS of pulling to get it off...LOTS!!)

Re: Fly Wheel Spinning

Thanks Guy's! Pulled the Fly Wheel and sure enough the key was broken again. It fits on there real snug and is now clean and oil free. I cranked her down real good - so - She is at least engaging. About to storm like crazy - so the tune up and running smooth will have to wait until next time.

Thanks again everyone !! I appreciate all the addvice.

Re: Fly Wheel Spinning

borrow a torque wrench and torque it.

Re: Fly Wheel Spinning

TD's right. You may think you have snugged it up hard, but I'll bet you didn't get the 100-105 ft-lbs it's supposed to be torqued to. If you didn't, it'll just shear that key again.

Trust me, it's a hard pull to get that torque, and you have to be holding the flywheel still while you pull. I was blown away at how much force it took to get that torque.

You'll need a flywheel holder (auto parts place) or a flat bar drilled to match two of the holes on the flywheel for the recoil starter mount to hold the flywheel while you torque it down.