1963 Johnson 40 hp, "clunking" when in forward

[Porto]

Hello, I have a 1963 Johnson 40 hp I took out today for the first time since I owned it. It idles fine but once I put it in forward the motor clunks or bucks at any speed. It doesn't seem to do it in reverse. I noticed when I was shifting from forward to nuetral the clunking got worse until I was out of gear. What does this mean?

 

[Paul Moir]

Re: 1963 Johnson 40 hp, "clunking" when in forward

It means you have a worn clutch dog and/or gearset. Unfortunetly.<br />I belive the clutch dog is still available from the dealer, and it isn't terribly expensive. <br />The gears are a different matter.

 

[Porto]

Re: 1963 Johnson 40 hp, "clunking" when in forward

Thanks Paul, I have 2 other 40hp Johsons for parts, both are RDS-22 model number. Will these have the same gears or not?

 

[Paul Moir]

Re: 1963 Johnson 40 hp, "clunking" when in forward

Yeah, I'm sure they do. One of them must be good.<br />If one of them got updated at one point, there'll be a detent between forward, neutral and reverse built right into the lower unit for more positive shifting. You'll be able to feel it when shifting the lower unit with the shift shaft while it's off. That helps prevent the clutch dog wear problem. Also, quickly shifting rather than easing it into gear helps a lot too.<br />I you do swap an entire lower unit, make sure that the amount of driveshaft sticking out of the lower unit is exactly the same as the one you've got. Some ones are just a little longer, and will damage the engine by pushing up on the crankshaft.

 

[Porto]

Re: 1963 Johnson 40 hp, "clunking" when in forward

Thanks again Paul. I will check to see if either of my parts motors has the detent. I was thinking I would remove the lower housing and only replace the gears (or whatever needs replacing) instead of the entire lower unit. Does this sound wise?

 

[Paul Moir]

Re: 1963 Johnson 40 hp, "clunking" when in forward

That's what I would do, but I over-do things usually. You'll need a new spagetti seal and o-ring for the seal carrier to reseal the case. I havn't had any luck with trying to reuse either. The easiest fix is just to swap entire lower units until you find the one that works.

 

[Porto]

Re: 1963 Johnson 40 hp, "clunking" when in forward

Both of my parts motors are long shaft, my running motor is short shaft, what does this mean?

 

[Paul Moir]

Re: 1963 Johnson 40 hp, "clunking" when in forward

That means that the driveshaft in the longshafts are longer than the driveshaft in the good engine. If you remove the water pump, the driveshaft should simply pull out of the lower unit, so you can still try the other lower units without disassembling them. <br />Don't forget to measure the shaft length from the lower unit seam to the top of the driveshaft before and after the swap.