1990 ish crankshaft question

[sblanco]

Hello everyone,

Long time reader but first time posting...

I have a mercury force 120, same old story of lack of compression due to piston damaged by ring failure. During tear down of engine I found the crankshaft is pitted and in need of re-building or replacing. The issue I'm having is I don't know exactly what year of engine I'm working on. The boat is a 91, the starter says 92 and the style of coils makes me think 93 for some reason...
I have found my crank has 15 splines.
My understanding is that there are two cranks that I may have 400-817859A2 1979-1993 115-140H with 15 splines, or I could have the 400-817400T3 1993-1996 120H 15 spline.

Is there even a difference between the 2? Some websites say they are the same and some sites say they are different.
I also forgot to mention that my pistons are bottom guided and 3.75. I also have the casting number on my crank 1780182. Not sure if that helps or not

Any help would be greatly appreciated on this
I'm hoping this makes sense to someone out there

Scott

 

[sblanco]

Hello

I’m hoping someone out there can help me on this. Maybe do I need to provide more details on the engine or perhaps maybe I’m missing something. I’m only able to find very conflicting info online and on engine part sites. I would like to know what crankshaft is correct so I can order parts and get this thing back together.

Thanks

Scott

 

[sajeschwab]

there is always a badge on the engine giving the year and manufacturing number. don't go off of a majority of the parts as they could of been changed, and a lot of the time the year the boat is released isn't the year the motor was made, especially if there had been a motor swap. on the inside of the cowling around the edge of the inside of the motor is wear the badge is usually. if you cant find anything for some reason id take it to a marine mechanic or get the service manual for the approximate age.

 

[racerone]

Is this an outboard motor ?----Or is it an engine used on a SPORT JET installation ?

 

[jerryjerry05]

On the block is a foundry stamp in 2 places.
The first is under the coils and packs.
It's a circle with he year in the center of the circle.
The other is under the bottom carb on the intake.

sajeschwab: the Forces stopped the tag back in 86
They went to a sticker on the transom assembly, which
in most cases fell off bleached out or became unreadable??

Pics of the cowl and the lower unit and the ignition parts.
Post those and maybe we can figure out the year?

400-817400T3 part# fits from 79 -94
[h=1]400-817859A2 was Superseded by 817400T3 -[/h]
One part looks like it was changed to the older #

 

[sblanco]

Thanks all for the help! I was able to find the foundry stamp as per jerryjerry05. Looks like its an 1989 MY
So it looks like i can order the 400-817400T3 crank.

Thanks again to all!

Scott

 

[jerryjerry05]

Look around and find a used motor.
Probably cheaper than buying a crank at $700