1978 Mercury 402 midsection swap

[Sam2]

Hello,
I have a 1978 Merc 402 short shaft that I rebuilt. Runs great, I replaced every rubber bit, every gasket, all the electric parts. Very reliable motor.

I would like to convert it to long shaft. I also have a 1971 leg from a 40hp. It looks pretty similar.
However, a 1971 midsection has a different part number than a 1978 midsection. It's quite an undertaking to swap all the parts.

I'm wondering if it'll work. Is a '71 midsection interchangeable with a '78 midsection?

Thank you in advance
Sam

 

[racerone]

Difficult to research this without the serial numbers.

 

[Sam2]

The 1978 good motor is SN 4860353.
The 1971 parts motor is SN 3175068.

 

[fastjeff]

I'm 90 percent sure it will.

Jeff

 

[Sam2]

Well that's encouraging. I guess I'll go for it and try. Worst case I spend a day i relaxing n the shop.

 

[Sam2]

It didn't fit. Oh well. Back to Paradise Boat Works to see if they have a later model leg

 

[racerone]

Look into finding an extension kit.----------Bay manufacturing-------May offer one.

 

[Sam2]

There's a Mercury junkyard an hour from me. Got to try that first. Can probably get a whole parts motor for $80 or so.

 

[timguy]

I have 76 402 LS here. Might part out. If it ever quits snowing I'll go back and look see. Gonna fix one with lower unit parts from the other. Will maybe end up with what you need, but won't be for a couple weeks....both motors are back in a semi trailer.....still snowed in. Gonna have one warm day, then cold again. Got snow again today.