I've removed the lower unit from this early 70's engine due to cooling issues. When looking at the parts catalog at the brp site, I noticed part 303261 "drive shaft pin". What's it's purpose? My engine was missing this part as I took it apart (I think), but I did notice the hole for the pin in the driveshaft?? Does it matter if it's missing?
That pin is what causes the propeller to turn.
There is a slot in the back of the prop that fits over the pin.
It's purpose is to break if the prop hits something so the shaft and/or gears won't be damaged.
The driveshaft pin is what olds the carbon seal and spring in place. There's a cup washer that rests on top of the pin. The carbon seal parts are quite necessary and help keep water from getting into the bottom end of the powerhead...
- Scott
Whoa there! The pin in question is what retains and drives the seal assembly parts 1 thru 6 in the diagram.
That seal is vital to the health of the engine. If it leaks, water goes up through the crankshaft bearing and is circulated throughout the powerhead via the oiling system. The seal is not working if the pin is missing and in fact the assembly may have fallen apart by now.
Tell ya what, if it were my motor I would pull the powerhead and examine the seal parts. I also would replace the gasket 303355 and o-ring 303347. Too much at stake here to ignore it or gamble and take a chance. Your choice.
Edit: Chinewalker and I were typing at the same time. You gotta be fast around here.
I learn good stuff every time I get into this forum.
Just the other day I was putting a new impeller in my brother-in-law's 6hp and had to knock that pin out to replace the impeller.
Was wonder what its purpose was, thought about not putting it back.
I did put it back and am very glad I did.
Shouldn't the tension from the spring pulled the whole assembly apart quickly? Removed the lower unit thursday, and was working on both the lower unit and the powerhead friday and saturday.. The parts are obviously still in place? Anyway, I am going to replace the part..
What if the part was missing since before? I know this engine's seen a shop before when it wasn't cooling. This weekend I was going to inspect the thermostat, but the housing was empty.. so the mechanic who worked on this engine seem to be a bit sloppy, and might also have lost the pin...?
This is a submerged engine I just got working.. runs better than ever, but doesn't cool at all, that's why I had it apart..
A little bit of history concerning that pin. That motor was "invented" in the 1950s as a 5.5hp. Back then you had to remove the powerhead before removing the lower unit. This was because there was no disconnect on the shift rod except right under the powerhead. And the reason they didn't provide a disconnect was because the seal assy would fall apart if you withdrew the shaft.
Fast forward to your 6hp. It's still basically the same stuff in there but they provided a ledge in the casting to hold the seal parts from falling apart when the shaft is withdrawn. There is a slot in the ledge for the pin to pass through, so the shaft has to be rotated so that the pin aligns with the slot before it will go through.
The reason I am skeptical is because who knows what has taken place with it having been ran all this time with no spring pressure on the seal to hold it all together. Maybe it is ok and maybe it isn't.
Anyway, I always thought it was a lousy move when they stopped forcing us to remove the powerhead to change the water pump. That 303355 gasket and 303347 o-ring don't hold up too good. Water pump time was the only time it got inspected. And now if the o-ring isn't up to snuff, when you go poking around in there with the shaft you are liable to knock it out of place. I just like to SEE what I'm doing. It's only about 6 or 7 screws to remove the powerhead.
Removing the powerhead seems like a nobrainer. But, this motor has been run in saltwater since new, and my grandfather (original owner) never cared much for maintenance. I'm worried about breaking bolts trying to remove the ph. Just getting the waterpump assembly off resultet in two broken screws. I'll definetly try and inspect seal, and replace the pin.
Evinrude 6hp - drive shaft pin?
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