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planomark

Member
"I picked up this lower unit f

"I picked up this lower unit from ebay for my '67 9.8. It was advertised as coming from a '69 9.8 with a serial number of 2708589, which does fall into the '69 range for that model. I just pulled the prop off the '67 unit and the first observation I have is my original prop shaft has six splines and the ebay unit has eight. And, the shaft on the 8-spline is a larger diameter, so the prop nut, plain washer and splined washer do not match. I'm already eyeballing a replacement prop since my original is a bit battered, but I am curious about the fit for the drive and shift shafts. Can anyone confirm that the drive and shift shafts on a '67 9.8 have six spines on each of them? Were the prop shafts changed between '67 and '69? My parts manual for '66-'69 Merc 110 does show two different part numbers for the prop shaft as well as for the shift shaft (short). But, there is only one part number for the drive shaft. I was really hoping I'd be able to simply swap out the entire lower unit and if all I need is a replacement prop and attaching prop nut, washer and splined washer, I'll be tickled.

Thanks, Mark."
 
Uh-oh. The Merc 200 (simi

Uh-oh. The Merc 200 (similar looking) has 8 splines. You may have bought a pink elephamt there. Sorry.

Jeff
 
"That's interesting... A p

"That's interesting... A prop is offered by a different source and is described as being for a 9.8, but it also has 8 splines. Lemme ask this... If I drop the original lower unit and the one I got from ebay matches up all around, am I safe?

Mark"
 
"If she bolts right up and the

"If she bolts right up and the driveshaft mates up ok, then all should be well. Any minor differences in gears in the lower will have such a minimal effect that you wouldn't notice.

Different gear ratio's etc on a large motor could be significant, but at this horsepower, all would be fine."
 
"Hi Graham and Jeff (and a

"Hi Graham and Jeff (and anyone else with two cents of reason to add),

I did some more research on this issue and looked at props. At the Maxrules Old Merc web site is a document on prop applications and they list prop numbers for a '68 110 (one year newer than mine) that don't match my parts catalogue. I looked up the part number for one of them and Quicksilver has it in stock and it is described as being for a 4, 6 or 7.5hp with 8 splines, just like I'm seeing on this unit I got from ebay. The other part about this is, considering the 8-spline is a larger diameter shaft and might have a larger gear end, thus reducing the rpms of the shaft, the Old Merc web site describes that prop being on 110 models with a lower rpm than the earlier (i.e. '67) models. So, on paper it is starting to make sense, but there is one more kicker to this.

As stated, the ebay listing for the lower unit said it came from a 9.8 with a serial number that matches up to '69, but when it arrived, it had a tag stating it was a "Merc 7.5" and the would also help to explain why the prop shaft has 8 splines. Knowing that there was a lot of cross-compatibility between 7.5 and 9.8 parts, I do feel a little more optimistic about this lower unit. Does my logic make sense and, if so, do you see any potentially grave issues?

Thanks,
Mark"
 
"Remember back when life was s

"Remember back when life was so much simpler? When Coke came in one flavor, and only in a glass, 8 0z bottle?

Gonna have to reason it out, parner.

Jeff"
 
"Well, guys, I look to be in m

"Well, guys, I look to be in much better shape. I drop the original lower unit to put ebay part on. Everything lines up. There was only one hitch, and that is the shift shat from my original is about 15" shorter than the shaft on the ebay unit, so I swapped them. And, more good news, the seller of the ebay unit has located the 8-spine prop washer and is sending it. Now, to find a prop...

Thanks guys. If it wasn't for the encouragement and advice from this board, I'd have lacked the confidence to do this on my own.

Mark"
 
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