This is part 1 of a series about my Johnson 6hp 1967 Outboard Gear Case / Lower Unit. (part 2, part 3, part 4 …)
Having already addressed the more pressing problem of the water cooling system, I realized the gear case was probably not water tight. The first sign of this was creamy “oil” leaking out of the motor when it was stowed horizontally in the boat (via the water intake screen) 🙁 In a strange way it was better than seeing nothing at all, which could have meant there was absolutely no oil left. As mechanic Leeroy Wisner warns:
There should be a dark thick gear oil. If it is a thick creamy color it has water contamination inside. If no oil comes out, your unit has a leaky shaft seal, which may have let water in and then over time also drained out if not ran for some time. If this is the case then you may have a rusty prop shaft or gears. Either of these will put a lot of excess resistance on the motor when shifted into either forward or reverse, causing it to bog down. <http://www.leeroysramblings.com/OMC_6hp.htm>
To start I followed some clear and simple video instructions from BRP – Marine Propulsion Systems on how to change the gear case oil:
I didn’t have much hope that changing the lube and the oil drain washers would fix the problem but, it seemed worth trying a simple fix first in case those washers were the source of the leak. And it did get me out on the water a couple times with my new (to me) boat. Thanks to the gang at Sherwood Marine (especially Chris) for parts, tools and advice. Here’s the first round of drained creamy oil and the Johnson Gear Case Lube Pump in action:
However after a couple of trips I noticed there always seemed to be a bit of a rainbow around the outboard when it was in the water, and on the last run I saw some strange bubbles once when I shifted from forward, to neutral and into reverse. Both of these symptoms suggested (to me) there was still a water leak that needed to be fixed.
The second time I drained the gearcase oil I got a little more clever and purchased a cheap $1.75 painting insert to catch the old gear case lubricant. Sadly it was totally creamy again:
I also realized that it is possible to get things done without a garage, workshop and outboard stand if you really want/need to! Please note I am lucky to have a very understanding wife, and accept no responsibility if you try something similar in your home 😉 You’ll also see some lumber there because I’m planning to build a Peter Nielsen (from Sail Magazine) outboard stand in the near future.
Right from the beginning of this process I was watching a tour of an old Johnson gear case by James at Highland Outboards. I watched it a couple of times in preparation and still went back for details when I was disassembling the gear case. It’s very helpful and I would highly recommend watching it before taking yours apart. Thanks James!!
To get the housing open on mine I had to stabilize the engine by pushing down on the lower unit / leg above the propeller shaft, so that I could also apply some very firm but gentle downwards pressure on the bottom of the fin, in order to pop open the old watertight adhesive/sealant. This caused me some concern as I was doing it, but everything worked out fine for me. I was glad I didn’t have to use a blow torch or chemical sprays to release the sealant (see note above about wife and living room workshop!).
Once inside the gear case, I was particularly slow at realizing that the shift rod and lever was still holding the propeller shaft and gears in the housing. At first I was wiggling the propeller shaft wondering why it was stuck, looking at one strange screw thinking perhaps I needed to take it out (more on that later), and wondering if some old adhesive / sealant on the main bearing was stuck. But I watched James’ video again and he didn’t mention releasing that screw, but he did push the shift rod down to create space, and once I did that the prop shaft and gears had space to slide out without any issue.
Thankfully once inside I only saw a tiny bit of normal wear and no real rust:
My metal fuzz seemed to be captured under what James called the main bearing and seal (what the Johnson website calls the head and bearing for the Johnson 1968 6hp CD-25A). As I worked the main bearing off the propeller shaft there was a gritty feel and I needed to add some oil and really roll it back and forth to slide it off. The fuzz all got captured in a hole on the propeller shaft:
Luckily the gears in the housing doesn’t seem rusty at all. There’s just a bit of rust around the old seals, so that seems to be one place where the water is getting in.
Stay tuned for part 2. I’ve got to run for Sherwood Marine before they close!
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