If you use/play with old outboard motors
long enough, you will come across a prop that the prop has become
separated from the hub. With many of these nearing or over 50
years old, your chances of finding even a used prop will be near ZERO
and probably the prop shops can't help you. If they could the
price would in all likelihood be more that the value of the motor.
If the rubber hub has just come unbonded, I have
cleaned everything and epoxied it back into the prop hub cavity. But
if the rubber hub as been deteriorated so badly , OR ruined by the owner, then
other methods need to be looked at.
I was approached by the owner of a 1965
Evinrude 5 hp motor, that when he tried to pull the prop, some previous owner
apparently never had it off or at least never lubed the propshaft. The
prop was seized so tightly that in pulling the prop, it came unbonded. But
the rubber and brass hub was still seized onto the shaft. OK a propane
torch was used , which in the process burned the rubber off, but the hub came
off. No problem, just find a used prop. Well this motor was only
made for 3 years and did not have a gearbox (forward/neutral/reverse), which
meant the prop rotated the opposite (LH) as most all other motors of near that
size. And he could not find a prop shop who dealt with that old or
size of motor. Well, I was never accused of not wanting a challenge,
so I agreed to repair it. The only reason I did, was that I had purchased
an identical motor a few years ago, rebuilt it and had not sold it yet.
I did a lot of asking at a local
contractor's hardware/lumber yard to see if I could find a caulking that would
set up hard. NOPE, as just the opposite, they want it to stay pliable
inside, and hard to the touch on the outside skin. And the cavity was so
large (without the rubber) that "Liquid Nails" would not really work. My
only resort now was to use fiberglass resin. But this required some
preparation.
OK, Where Do I Start ? : First was to clean everything, and get rid of any
old rubber or grease. This entailed inspection of the prop, which I found
a plastic/Nylon shim inside against the rear inner end. This had to come
out and the whole inner part sandblasted to remove rubber and any grease, but to
also supply a rough surface for the fiberglass to adhere to.
On this prop, the shaft size was 1/2" while the rear, threaded nut was 7/16".
There is a large washer with the 7/16" hole that fitted in a recess on the rear,
so a stub shaft was made to accommodate these dimensions
Then the bronze hub was placed in my metal lathe and
COURSE threads ran on the center section, again for the purpose of ensuring better
bonding.
My plan, was to injecting fiberglass resin in between
the hub and prop. But, this resin is very liquid and to keep it from
running out the rear, I used the stub shaft as alignment along with the washer
and by before it was in place, applied a ring of caulking around the rear outer
hub. Applied some Vaseline on the outside under the washer to protect any
unwanted adhesion, then slid the hub down the shaft, clamped the shaft in a vise
allowing the caulking to settle down as the prop was held with the front
pointing UP. I then let this set up for a day.
Next, I used a 1/8" carbide cutter in my Dremel tool,
and on this model, the shear pin slots were on the front/larger end of the hub.
Here, off the ends of the shear pin slits, I cut in with the Dremel tool cutter
about 1/2 depth of the cutter. Then after the caulking was set on the rear, I drilled
the rest of the 1/8" hole in the prop inner housing edge aligning with these
precut shear pin cuts, making a 1/8" hole on each side down into the cavity.
Now at a farm store I purchased a couple of
12CC hypodermic syringes, which had the same outside dia. of my 1/8"
drilled holes. I mixed up about 10CCs of resin and a few drops (like 4) of
hardener, mixed that and quickly plugged the outlet hole of the syringe with a
finger, then poured in the resin and then inserted the syringe nozzle into the
hub hole and slowly injected this resin. If you dally too long and or the
weather temperature is warm, you may not get it all injected. I then
quickly cleaned the syringe with Acetone and let the hub set up. An hour
later did it again, until the cavity became full, as indicated by it coming out
the other hole.
1986 5hp OMC prop, stripped
down with the hub on the left
I then cleaned up any excess unhardened resin
using paper towels and a number of Q-Tips.
Here you see the resin FILL holes on the ends of the shear pin
slot
Another One : OK,
now we have another hub, but this time it is off a 1957 3 hp Evinrude Ducktwin.
Again with the possibility very slim in finding replacement parts. This
prop had numerous ridges inside the prop housing, with more numerous ridges on
the outside of the hub. There was a rubber coupler that looked like a
double cogged automotive timing belt but with cogs on both sides that slid in between
both the hub and the prop tying them together. Over time (60 years), this
rubber coupler deteriorated enough that it allowed the prop to slip on the hub.
Dumb me, I did not do my
research, as this part (#0315471
- Propeller Clutch Ring)
is still available at a price of $33. As a side note - later I found that on
the older T series Johnsons that they also used a similar rubber
"clutch/shock absorber" ribbed rubber bushing. Not sure that
it would interchange, but I guess, don't take it for granted, just because
it is an old motor.
Here I used the same method as previously, only
here the owner had tried to fix it by squirting silicone sealer in between
the three parts, which can be seen in the photo below. The hub was
wire wheeled to remove the silicone and rubber, but the prop required
sandblasting.
Here you see the damaged prop and cleaned hub.
This motor again uses a shear pin, but on this
one it is recessed into the prop about 1/2" deep. Again a stub
shaft was lathe turned to fit the hub when doing this project, which
allowed me to, before the fiberglass was set, the prop could be rotated on
this shaft and eyeballed to rotate concentrically as nearly as possible.
This prop was a bit different in that it had a hard plastic (?) bushing at
the rear that pretty well sealed the fiberglass from running out as was on
the 5hp prop. And the prop shaft was smaller (7/16"). Here I
also used the 12CC hypodermic syringe to inject the resin where I wanted
it, instead of it running over which would have required a cleanup.
These syringes were sacrificial but for a price of under a dollar was
worth it.
Here you see the two parts fiberglass resin boned together
Here you see the T series prop & it's other component parts
Something I found on FaceBook
When you can't find a good welder & the fish are biting
