Merc 110 vs Merc 40 Lower

[tbh051407]

I'm new to the forum and just got a 66 Merc 110 (s/n 1907931) for a decent price (or so I thought) from a guy nearby. I cleaned the carb, rebuilt fuel pump, and adjusted points to get the motor running flawlessly.

My delimma: evidently the bearing on the forward gear bearing had seized and the pinion gear sheered off teeth from the from the forward gear.

I've found a couple 9.8 lowers at a repair shop nearby but where the cavity on the lower butts up to the driveshaft housing, they aren't the same size.

My question: I've found a lower on ebay that fits a Merc 40 (supposedly 69) and the distance the cavity extends back on the cavitation plate looks identical to mine. The prop shaft has a different part number but the gears and driveshaft are the same. Would this lower work with my motor? Does anyone know or have expertise with these earlier mercuries?

Thanks in advance

 

[Chinewalker]

It won't work as you won't be able to find a 9.8 hp prop that will fit and the 4hp prop won't give you enough bite. BUT, if you're handy, you can swap the good gears out of your 4hp lower into the 9.8 housing, mixing and matching what you need to get it together. Keep an eye on bearing condition, seals, shaft surfaces, etc. as Mercs of that era are notorious for water intrusion due to poor sealing. They used a carbon steel shaft with plating over the seal areas, such that as soon as the plating wore a bit, the shaft would rust, letting water into the housing.

 

[tbh051407]

That's what I was afraid of.

Getting the lower for the gears and other parts was my second thought. Shimming the new gears correctly is my only fear.

The motor may not have been a good buy after all.

 

[tbh051407]

Let me pose this question. Could I simply just swap out the prop shaft? Is the actual size or demisions of the gear cavity different from the 9.8?

 

[Chinewalker]

I think that would work fine. The gear placement and their shimming are dependent on the housing, not the shafts. I think as long as you kept the gears and housing together with related shimming, you should be okay.

 

[tbh051407]

Thanks! I really appreciate your help. It's been well received.