1987 85 HP lower unit on a '83 115HP?

[Danny C]

Will it work? Is there somehow I can check this?

 

[Chris1956]

Re: 1987 85 HP lower unit on a '83 115HP?

The '87 85HP motor is a 4 cylinder? If so, it will work. If the 85HP motor is a 3 cylinder, I do not think it will fit.

 

[Danny C]

Re: 1987 85 HP lower unit on a '83 115HP?

Thanks Chris, what about a '75 1500? If you havent figured it out, I am looking to replace the LU on my 115 and am looking through craigslist...

EDIT... Just found out the 85HP LU came off a 3 cylinder...So, it sounds like that will not work. That is very unfortunate. It would have saved me a ton of money. Is there anyway to make sure it will not work? check serial numbers or something?

Also, if it doesn't fit, is it just the housing that is not compatible or is it other stuff as well? Would I be able to scavange parts from this to put in my 115?

 

[Chris1956]

Re: 1987 85 HP lower unit on a '83 115HP?

The gearbox off the 1500 will fit. Not sure what the differences between the 3 cyl and the 6 cyl gearboxes are.

 

[Danny C]

Re: 1987 85 HP lower unit on a '83 115HP?

Ok, how about a '74 mercury 125? Survey says...

Also, is there way to look this up? I hate to keep asking on here.

Thanks

 

[emckelvy]

Re: 1987 85 HP lower unit on a '83 115HP?

There's no such thing as a '74 125hp, but if it's an Inline Six, it should fit!

Any Inline Six lower unit from around '66 to the last year (1987) can be made to fit. They all have the same mounting bolt pattern. About the only significant difference is whether or not it had an O-ring groove for the driveshaft-to-crankshaft seal.

An '83 115hp doesn't require an O-ring groove in the driveshaft; you'd need to fill up the O-ring groove on an older L/U with JB weld, epoxy, or similar, and make the filled area flush with the driveshaft, so that area would slide smoothly thru the O-ring which is installed in a stainless assy pressed into the end of the crankshaft.

Your 115hp used a 2:1 gearbox, a few years had a different gear ratio but if you happened upon one of those, all you'd need to do is change the prop pitch to match.

The 3 and 4-cyl Big Bore gearcases are completely different from the older-style and have a different bolt pattern.

Check your local Craigslist, you may find a deal on a parts motor.

HTH..........ed