Johnson AD11 1957/ 7.5hp. water in lower unit

[gary57]

I just bought a 1957 AD11 7.5hp. Johnson from the man that bought it new in 1957. I am a first time poster so please bear with me. I just received all the manuals. The motor runs great, pumps great water..... runs strong, but
I did find water in the lower unit, bummer. I drained & replaced with new gear oil, ran for about two hours checked, water was back. I pulled the prop found about 10 years of fishing line around the prop shaft. Here is my question...... is there no way to replace the prop shaft seal with out tearing into the whole lower unit from above?
I am a Mech. Engineer & find it hard to belive that an Engineer would design this motor that way. Can the lower unit be split with out having to start at the power head? If you turn the motor up side down & just remove the lower part with the skeg up, will all the gears not stay in place? Any tricks up any ones sleeves? One more thing..... I am going to replace the pull rope can you not pull the rope all the way out clamp it from recoiling cut the old & feed the new rope through with out going through what the manual says? Thanks for any help. Smooth Boating

 

[JB]

Re: Johnson AD11 1957/ 7.5hp. water in lower unit

The most common cause of water in the gearcase is re-use of the gaskets under the vent and drain plugs, Gary. Those are crush gaskets intended for one time use.

Given the age of the engine and the fishing line wrap-up you may also have damaged seals on the propshaft.

I would try new gaskets under the drain and vent plugs first. Buy a bunch, they are cheap.

 

[Mas]

Re: Johnson AD11 1957/ 7.5hp. water in lower unit

You could also do a pressure/vacuum test on the LU to pin point the leak & replace that seal. You may be better off just doing a total reseal, however.

MAS

 

[wbeaton]

Re: Johnson AD11 1957/ 7.5hp. water in lower unit

Buy a bunch, they are cheap.

I just paid $12 CDN for 10 of them at my dealer.

You have to remove the powerhead to drop the lower unit. If you've done it before its not too bad. If you haven't then its time to replace the impeller anyway so this is a good time to do it.

+50 years is a lot to ask from an oil seal. I have yet to find an original 1950's OMC with good seals.

 

[lindy46]

Re: Johnson AD11 1957/ 7.5hp. water in lower unit

I am a Mech. Engineer & find it hard to belive that an Engineer would design this motor that way. Can the lower unit be split with out having to start at the power head? If you turn the motor up side down & just remove the lower part with the skeg up, will all the gears not stay in place? Any tricks up any ones sleeves?

You can remove the bottom half of the L/U without removing the lower unit from the motor. The problem is, there is a little Phillips head screw which connects the shift rod yoke which pivots on the clutch dog. That screw must be removed to remove the bottom half of the case. Once removed, it is VERY difficult to get it back into the shift rod yoke without the L/U off. You could try it - the worst scenario is you will have to pull the powerhead and remove the lower unit. I have taken that screw out and had it go right back in, but sometimes it's a bear to re-align.

 

[wbeaton]

Re: Johnson AD11 1957/ 7.5hp. water in lower unit

You can remove the bottom half of the L/U without removing the lower unit from the motor. The problem is, there is a little Phillips head screw which connects the shift rod yoke which pivots on the clutch dog. That screw must be removed to remove the bottom half of the case. Once removed, it is VERY difficult to get it back into the shift rod yoke without the L/U off. You could try it - the worst scenario is you will have to pull the powerhead and remove the lower unit. I have taken that screw out and had it go right back in, but sometimes it's a bear to re-align.

You have to remove the ENTIRE lower unit from the motor to reseal the gearcase. The above will only get you access to the spaghetti seal (skeg), Gearcase head and propshaft seal. You will still need to remove the lower unit to access the driveshaft seal and shiftshaft seal.

 

[gatzkemj]

Re: Johnson AD11 1957/ 7.5hp. water in lower unit

My father-in-law just gave me a 57 for my duck boat, and it was running flawless until the shift rod broke apart from the shift knob. I pulled the L/U and it looks like I'm not going to be able to get at the shifter unless I remove the powerhead completely from the lower shaft housing. If anyone has any insight on how I might do this I would really appreciate it. I've worked on a few Mercury's before, but this motor is an old Johnson and I'm really in another era of engine repair here.

 

[Mas]

Re: Johnson AD11 1957/ 7.5hp. water in lower unit

You'll want to start a "new" thread...instead of tacking on to a thread that's over a year and a half old. Title the thread "broken shifter". Give the year/make/model too! I would love to help you, but I am not familiar with your motor.

You'll get help fast.

Mas