1958 18hp Johnson Forward Gear issues

[bhughes]

I've got a 1958 18hp johnson I'm trying to get going. As far as the engine goes, it cranks up pretty easily and runs fine in neutral. It doesn't exactly idol properly as I can't turn the throttle far below the start position without it dying, but I'm not worried about addressing that yet.

The biggest issue is trying to go in forward gear. The first time testing it out on the water, it started going forward at first, then the motor start knocking every 3 or 4 seconds, then it sort of popped out of gear and wouldn't go forward anymore. After reading up on it, I took off the LU and looked at the clutch dog. It did have some slightly curved edges on the teeth but not sure how bad. Just to try it, I flipped it around since reverse seemed to work okay. After putting the LU back on and putting it back in the water, it was pretty much the same issue. Then, I tried pulling the shifter handle up past the last notch where it is normally in forward gear position. This allowed me to pull the lever up another inch or so. This seemed to keep it in gear, but I could not get the motor to rev up at all in gear and it was still popping out of gear if I let go of the lever.

I've ordered another lower unit since I think it might be the clutchdog, but I was also wandering if I need to adjust the shift rod height or if there's also a problem with the engine since it wouldn't rev up.

Any suggestions are appreciated since I know very little about motors.

 

[bhughes]

Re: 1958 18hp Johnson Forward Gear issues

Any suggestions would be great.

 

[lindy46]

Re: 1958 18hp Johnson Forward Gear issues

It probably is a worn clutch dog/forward gear, but it also could be misadjusted shift rod. You may want to check the shift rod coupler - remove the plate on the leg of the engine and make sure the upper and lower shift rods are connected properly in the coupler. There is an indent in the ends of the shift rods, and the coupler bolts MUST pass through those indents.

 

[bhughes]

Re: 1958 18hp Johnson Forward Gear issues

I've messed with the shift rod coupler a few times. The bolts are in the right places b/c they don't really screw in unless they line up with the grooves on the shift rods, however, I have not tried to adjust the height of the shift rod b/c I didn't know how to do that. I think from reading on here it seems you just screw the shift rod on the lower unit to move it up or down?

 

[lindy46]

Re: 1958 18hp Johnson Forward Gear issues

On that motor, there is no adjustment to the shift rod length. You may be able to adjust the shift lever some. I believe there are two bolts on the lever which have to be loosened to adjust it. If the rod is firmly in the notch when you are in forward gear, it should be adjusted properly. Another thing I just thought of - has that little Phillips head screw in the side at the bottom of the lower unit been removed? That screw holds the yoke which operates the clutch dog. If that screw doesn't go though the hole in the yoke, you've got problems.

 

[bhughes]

Re: 1958 18hp Johnson Forward Gear issues

I think your refering to the clutch pin which acts as a pivot for the clutch to move in and out of gear. It's in correctly. Plus, it does go into gear, it just doesn't stay in.

I tried to see if there was somewhere on the shift lever to adjust it, but I couldn't see any place unless there's something toward the inside of the motor which looks like it would be tough to get to.

I've got a replacement lower unit that I got off ebay that I am going to put on this weekend. I hope that it works once I put it on, but if not and its the shift rod lever that needs adjusting, I need to figure out how to do that.

Any idea if any of this would cause the motor not to be able to rev up when I'm holding it in gear?

 

[lindy46]

Re: 1958 18hp Johnson Forward Gear issues

Any idea if any of this would cause the motor not to be able to rev up when I'm holding it in gear?

No, that sounds like either an ignition or carb problem.

 

[bhughes]

Re: 1958 18hp Johnson Forward Gear issues

Does it makes sense that it would rev up fine in neutral, but just not when I hold it in gear? Would it matter that much if the high or low speed adjustments are not perfect?

 

[lindy46]

Re: 1958 18hp Johnson Forward Gear issues

Does it makes sense that it would rev up fine in neutral, but just not when I hold it in gear? Would it matter that much if the high or low speed adjustments are not perfect?

Unless something is binding/worn in that gearcase - changing the lower unit will answer that question. Could be several things: low compression, bad coil, dirty carb, mis-adjusted carb, pressure leak (I assume it uses a pressure tank). Hopefully, since it starts pretty easily, compression is ok. But you may want to check compression before dumping any more money into it. If compression is ok, most everything else can be easily addressed.

 

[bhughes]

Re: 1958 18hp Johnson Forward Gear issues

Great news! I replaced the lower unit with the one I got off ebay and the motor works awesome!

When we got in the water, I put it in gear and it went into gear perfectly. However, it still wouldn't rev up like before. Then, I started tightening the high speed adjustment knob and after about a half turn in or more the motor started reving up and getting a little fast and a little futher turning and it hit full speed. It was great.

Before, with the old lower unit, I couldn't tighten the adjustment knob b/c everytime I did it would pop out of gear, so I couldn't tell if it would rev up.

Thanks for your suggestions, I'll try to post a pic soon.

Brandon