This is part 3 of a series on my Johnson 6hp 1967 Outboard Gear Case (part 1, part 2). Here I’ll illustrate the dis-assembly and the troubleshooting. All the part numbers refer to the Johnson 1968 6hp CD-25A 1968 Gearcase Group schematic on shop2.evinrude.com.
The propeller was easy to slide off, after removing the cotter pin. The picture is a little dark here, but if you click into the larger image you can see the Drive Pin (307949). This is often called the “Shear Pin” because if you hit or tangle something in the water it’s designed to shear off / break and let the propeller spin free so excessive force doesn’t travel along the propeller shaft into the gears and up the driveshaft into the engine. I’ve been told it’s wise to carry a couple of spare shear pins with you in case you need to replace one in the wild.
In the next image below you can see the Shift Lever Pivot Pin (308376), note that the head has a cross / Phillips head on it. When you’re doing a basic oil change (like in the video at the beginning of part 1) this is the “screw” that people sometimes mistake for the oil drain plug and washer (307551). The oil drain plug has a flat / slotted head on it. If you remove the shift lever pivot pin, and your shifter lever (303340) stays in place, then you should be able to just slide it back in without issue. You’ll know that it slid in properly if you can shift from neutral into forward or reverse because this is the pin that connects the shift rod (309582) to the cradle (303381) that snugs right onto the clutch dog (377458). But if you remove it, and that shifter lever moves, then you might have trouble getting the pin through both the hole in the outer housing and the two holes on the top of the shifter lever (see image below). Anyways, the seal / washer (307853) on this pin was looking pretty rough, and even though I never saw lube leaking out of it I’d say it really needed replacing.
Below is a picture of inside the gearcase where I’m removing the little cotter pin (306376) that holds the shift rod pin (302504) to the shifter lever (303340). Towards the lower right of the picture you can see the two holes in the shifter lever that the pin (in the picture above) needs to slide through after it’s entered the housing. I was really relieved that even though I had a fairly serious oil leak and I’m using the outboard in salt water there was no rusting of the gears inside the gearcase.
Once you get that shifter lever disengaged from the shift rod, then the whole propeller shaft and gear assembly lifts out really easily to expose the pinon gear (312108) that’s attached to the driveshaft:
Here’s the whole gearcase group exploded a bit, with the front bearing (303380) and gear and bushing (377152) off the propeller shaft:
This is the main head and bearing (382291) and the reverse gear (305216) sliding off the propeller shaft:
And this is a close up of the front bearing (303380) and gear and bushing (377152) and one of the thrust washers (303361). You can also see the cradle (303381) and clutch dog shifter (377458) to the right of the image:
This spaghetti string gearcase seal (309044) looked pretty compressed and worn out, but I never saw oil leaking from the housing itself. So while it probably didn’t help, I don’t think it was the main source of the problem:
When I lifted the impeller housing plate (303376) it was really ugly looking underneath inside the impeller housing and retainer assembly (382796)! This is what slowly clued me into realizing that there was an oil retainer there (either CD-25A 0-314167 or CD-25C 0-300599), which seals around the drive shaft. It seems that oil retainer is probably the primary problem!
Below is an image of the same impeller housing and retainer assembly after being cleaned up a little so you can actually tell there’s a separate oil retainer part in the middle. It’s hard to see, but in this photo the old oil retainer that is currently there in the impeller housing and is not working is stamped “300599” which corresponds to the schematic for CD-25C. However the driveshaft does wobble in this, either because of wear and tear, or because someone in the past installed the wrong part. Hard to know.
It is worth noting that the schematic diagrams for both CD-25A and CD-25C show the gearcase head oil retainer on the propeller shaft as part #313282. However in my engine there’s an old oil retainer there stamped “303345” which seems to be a generic Sierra OMC part based some Google searches… This suggests someone had this engine apart in the past and I’m not looking at factory settings for any of these seals.
Below is an image of the new oil retainer I’m going to use (CD-25A 0-314167). I picked this part based on my hypothesis in part 2, which matches with Leeroy’s hypothesis. To save you a click, I decided that my 1967 Johnson Seahorse 6hp model and run/version number CD-24D was probably built later in the year 1967. I also decided that the schematic for the 1968 Johnson Seahorse 6hp model and run/version number CD-25A was probably earlier in the year 1968, and therefore they had a greater likelihood of having similar parts. In the real working world if you were building engines right before Christmas and then came back after New Years there probably wouldn’t be a lot of change in how you built the engines. However if you have more information on the run/version numbers please us know in the comments below! Normally people in the 20th century numbered things 1-2-3 A-B-C, but sometimes people came up with other wacky ID formulas. Also, I am not a trained mechanic, and I’m accepting the risk that I’ll have to do this all again with different oil retainers if I’m wrong about the impeller housing oil retainer CD-25A 314167 versus CD-25C 300599.
The new oil retainer is roughly the diameter of a quarter. If you click and open the larger image you can see the very cool little spring that synches the rubber seal inwards to seal around the driveshaft as it passes down through the impeller housing into the gear case. This new part #314167 slid over the driveshaft easily and feels quite snug – so far so good. Gotta remember to put some grease there so the rubber doesn’t stick, twist or burn on the first use.
More in part 4 on how successful I was at removing those oil retainers and bushings 😛