Mercruiser outdrive interchangability?

[reelfishin]

I have several good used Merc 110 and 120 out drives, I no longer have an I/O boat but am in need of an outdrive for an older Mercury 85HP inline 6 outboard.
I was wondering if I can use an I/O outdrive on an outboard? It appears as if I can just swap drive shafts and it should fit?
I realize that the gear ratio may be different, but I can adjust for that with a prop change.
The bolt pattern and diameter look the same.

Does anyone know if this will work?

 

[Bondo]

Re: Mercruiser outdrive interchangability?

Ayuh,....

The gear cass are Much Larger on the Outdrives...
They're physically Larger,+ won't bolt up....

 

[chiefalen]

Re: Mercruiser outdrive interchangability?

I have seen people put the wrong gear ratio drives on boats, thinking they can adjust for it with the prop never works.

They wind up doing it twice, three times till they "do it right".

 

[Don S]

Re: Mercruiser outdrive interchangability?

Won't work. Not only is the bolt pattern different, the vertical shaft and shifting are different, the exhaust opening is completely different, and like bondo said, it's just too big in physical size.

 

[reelfishin]

Re: Mercruiser outdrive interchangability?

Thanks for the replies.
I thought that maybe since it bolts up it could be made to work by swapping the shafts. I was going to just swap over the shifter rod and drive shaft and give it a try. I had it bolted up minus the shaft, so the bolt pattern is the same. I was thinking that maybe they used the same housing for all of these older lower units. The prop from the outboard and the I/O were the same too.
I have a 65HP I can borrow the lower from for now I guess, I'll see if I can get the original on apart to see what when wrong.

 

[Bondo]

Re: Mercruiser outdrive interchangability?

The prop from the outboard and the I/O were the same too

Ayuh,.... Only the propshaft size,... The Outside Diameter is different...

The old Outboards are a 4" gearcae,+ the I/Os are still a 4, 1/2" gearcase....

I also think that the old 65hp motors used an oddball lower gear Ratio,...
You probably won't find a prop pitched right to make it work...

 

[reelfishin]

Re: Mercruiser outdrive interchangability?

The case is larger, but only by about an 1/8" either prop fits and looks like it could be right. The I/O prop was a 15 3/4" x 17 pitch, the 85 HP had a 13"x14P prop, I have plenty of props to choose from if that's the only issue.
By turning the shaft on the I/O lower and on one from a Merc 1150, they seem the same, if not very close or too close to tell by hand.
The 1150 to 1350 Inline 6 motors do have the larger diameter gear case but they too bolt on, I am thinking that maybe the I/O is using that gear case?

The 650 and 850 have the same lower unit, but I believe there was a change in these in 1970, I'm not sure what it was, but there's a difference in the shape of the skeg between the 1965 850 and an newer 850 I have here.

I'm more looking for a reason to make use of the I/O drives, I no longer have or intend to have anything with an I/O, so it's either sell it and rebuild the old lower unit or make use of it. I'd rather make use of it since it's so clean.
Its hard to find good lower units around here with all the saltwater corrosion. Especially older ones.