1956 Johnson 30hp Motor Jumps When running.

[rgballard]

Need help yet again. When running in forward, neutral or reverse the motor jumps or thuds. At first we thought it was because the motor wasn't locked down (mechanism was broke), so I fixed that and didn't seem to have any problems with it for a while. It is back to jumping/thudding again. It jumps more at WOT then at idle.

I had a friend drive the boat today while I sat in back with the motor and watched it. At first I thought it was the lower unit, but now I think it is something up top. Messing with the High Speed needle seems to change the thud it is making. I have attached a link to the video.

I would really appreciate any advice. Thank you.

http://youtu.be/qP0Mi6BYaCU

 

[kfa4303]

Re: 1956 Johnson 30hp Motor Jumps When running.

Hi rg. I think you may be slipping into/out of gear. If so it could be due to a variety of issues. The simplest is to check the shift shaft rod connector and the shift cables in your controls to be sure all is well. However, I think it's actually a worn clutch dog. The classic symptom is a motor that runs well but feels like it's hitting a submerged log, or other object. The only way to know for sure is to open up the lower unit and check. It only takes a small amount of wear on the lobes (dogs) for the motor to slip out of gear. Do a search here in the forum and you'll find all kinds of threads with pics.

http://www.marineengine.com/parts/v...ntage-evinrude-johnson/376750/37675000001.htm

 

[rgballard]

Re: 1956 Johnson 30hp Motor Jumps When running.

Sounds like it's time for a lower end rebuild. Your description of hitting a submerged log is exactly what it feels like. Seems to be getting worse too, which would lead me to believe it is something wearing out too. Thanks for the input.

 

[kfa4303]

Re: 1956 Johnson 30hp Motor Jumps When running.

It's not that uncommon, really and the motor is 50+ yrs. old after all. Once you see it you'll be amazed that all the power in the motor depends on two little lobes. Newer clutch dogs have 3 or more lobes on them to reduce this problem. Do a search here in the forums for pics of other worn dogs. It only take a small amount of wear to make them go bad. You can try flipping it around rather than replacing it outright, however REV will then slip, but if you don't use it much it may be worth doing. The replacement part is usually not cheap, so I would ask around here in the forums and/or check aomci.org and ebay to find it. You'll probably also want/need to reseal the LU while your at it. You can get a reseal kit right here at iboats for about $25. There are lots of threads that can walk you through that job as well. Keep us posted. Holler if you get stuck.

 

[boobie]

Re: 1956 Johnson 30hp Motor Jumps When running.

I vote for clutch dog and gears and maybe worn shift linkage which caused the problem to start with.

 

[rgballard]

Re: 1956 Johnson 30hp Motor Jumps When running.

Well have water in the Lower Unit Oil so I decided to tear it apart regardless (figured resealing it was worth it) to see what the clutch dog looked like. Here are some photos, honestly I think it looks fine to really good. What do you guys think? I also tore a part one on another motor I had (for practice first) and it looks way worse (all rusted and bearings that don't work). I think that this is all in good shape. I think maybe the problem might be where the two shifting rods connect, possibly.



I am happy everyone seems to think it is shifting issues that gives me somewhere to start.

 

[lindy46]

Re: 1956 Johnson 30hp Motor Jumps When running.

Photos a little blurry, but doesn't look too bad to me. Have you tried adjusting your shift cable end to pull the shift lever a little more forward? Also try disconnecting the cable and shift it manually into forward and see if she does the same thing. Any play in the shift lever? Next step would be to check for play in the upper shift rod - use a long-nosed plier and reach through the window in the side of the leg and grasp the shift rod. Check for play - there should be no up and down play.

 

[oldslowandugly]

Re: 1956 Johnson 30hp Motor Jumps When running.

I had two of that great motor and both needed the same repair, clutch dog as well as gears. If you look closely at the dog and the inside of the gears, you will notice a reverse bevel. They interlock and hold onto each other when engaged. The worn lips of the dog can't hold the gear, and you get the jumping out of gear. Absolutely get a new dog, and take the gears to a dealer. Compare the inside bevel to a new gear and make a determination if the gears are worn too. Mine were. When you seal up the gearcase, use all new seals. Check both of the shafts for grooves at the seal locations and if so replace them or restore them by filling the grooves with Marine-tex and wet-sanding flush. Use plenty of OMC Adhesive "M" on the "O" ring and spaghetti seals. Pressure test the gearcase for both 20 psi positive and 20 hg negative pressure. I made an adapter that screws into the upper oil fill hole and use a bicycle pump and Mighty-Vac to test with. If it passes, you will not get any more water in the oil. FWIW those parts are in beautiful shape for a '56.

 

[rgballard]

Re: 1956 Johnson 30hp Motor Jumps When running.

So after further exploration I discovered that the clutch dog doesn't slide all the way forward on the prop shaft. It stops about an eighth to a quarter of an inch. After playing with it for about an hour or two I was able to get the clutch dog to go on from either side of the prop shaft and slide smoothly. I couldn't really see any damage to the teeth on the prop shaft or clutch dog. They both look really good, but obviously it wasn't going all the way forward which would lead me to believe that this is why I haven't been able to shift into forward gear all the way.

I would assume that the clutch dog should slide onto the prop shaft from either direction right?

 

[lindy46]

Re: 1956 Johnson 30hp Motor Jumps When running.

Should slide on either direction. Can't imagine what would keep it from sliding all the way forward. Was there rust or burrs on the propshaft splines?

 

[rgballard]

Re: 1956 Johnson 30hp Motor Jumps When running.

There were a couple burs on the propshaft splines, but they were loose. I was able to pick them off. I have been sliding the clutch dog back and forth and taking it off rotating it and sliding it back and forth it seems to be working ok now.

 

[kfa4303]

Re: 1956 Johnson 30hp Motor Jumps When running.

good. you should be able to slip it on and off like a ring on a finger. try to put the best side facing the FWD gear.