1978 evinrude 70HP driveshaft removal from lower unit

[78 evinrude]

I had picked up a replacement lower unit but it has a short drive shaft in it and i need to replace it with the long drive shaft. How do i get the shaft out of the lower unit? I have removed the water pump housing and impeller, the set of needle bearings under that, and the locking screw by the water intake on the side. Do i need to remove the prop shaft? if so than how is that done. I'm at a loss and getting fustrated with it. :grumpy: Will post pictures this afternoon

 

[gm280]

Re: 1978 evinrude 70HP driveshaft removal from lower unit

I had picked up a replacement lower unit but it has a short drive shaft in it and i need to replace it with the long drive shaft. How do i get the shaft out of the lower unit? I have removed the water pump housing and impeller, the set of needle bearings under that, and the locking screw by the water intake on the side. Do i need to remove the prop shaft? if so than how is that done. I'm at a loss and getting fustrated with it. :grumpy: Will post pictures this afternoon

First of all Welcome to iboats :welcome:

Okay for starters, there is a nut underneath the drive shaft and pinion gear in the lower foot section. So you will have to open up the entire foot to remove that drive shaft. You can see the IPB for your engine at:

Okay this site won't allow me to post the web address. So search for you engine on the site for the parts section and you will see how it is put together.

May not be a bad idea to install some new seals and impellor while you have it this far down too. They only made one model of your engine for that year and this should be your engine model number; 70873C Hope this helped...

 

[Chinewalker]

Re: 1978 evinrude 70HP driveshaft removal from lower unit

I don't think the short driveshaft lower unit will even fit the long shaft mid - different housings. The short shaft used what was essentially the 50hp gearfoot with a different driveshaft to work with the 3-cylinder crankshaft.

 

[78 evinrude]

Re: 1978 evinrude 70HP driveshaft removal from lower unit

First of all Welcome to iboats :welcome:

Okay for starters, there is a nut underneath the drive shaft and pinion gear in the lower foot section. So you will have to open up the entire foot to remove that drive shaft. You can see the IPB for your engine at:

Okay this site won't allow me to post the web address. So search for you engine on the site for the parts section and you will see how it is put together.

May not be a bad idea to install some new seals and impellor while you have it this far down too. They only made one model of your engine for that year and this should be your engine model number; 70873C Hope this helped...

Thanks for the welcome, this is my first boat and i'm guessing that i'll be on here alot as i go through it. To get the prop shaft out do i need to use a wheel puller to get the BEARING HOUSING ASSY (#25) out first? I have already removed the 4 bolts (#29) holding it in.
I take it the NUT, Pinion to d'shaft (#31) is the nut your refering to that has to come off before removing the shaft.

Below is the diagram i am using.

 

[78 evinrude]

Re: 1978 evinrude 70HP driveshaft removal from lower unit

I don't think the short driveshaft lower unit will even fit the long shaft mid - different housings. The short shaft used what was essentially the 50hp gearfoot with a different driveshaft to work with the 3-cylinder crankshaft.

ok not to sure, but the units are identical except the shaft is short. they both have the 4 spline shaft. The marina i got it from said it would work but they wanted $400 to swap out the shafts.

 

[Chinewalker]

Re: 1978 evinrude 70HP driveshaft removal from lower unit

Interesting. Might be from a different year, then, as the 1978 short shaft uses a small gearcase, common to the 50.

 

[78 evinrude]

Re: 1978 evinrude 70HP driveshaft removal from lower unit

Interesting. Might be from a different year, then, as the 1978 short shaft uses a small gearcase, common to the 50.

Are there any easy ways to identify if it is the small one? Would the overall size be smaller or just the gears are diffrent?

 

[Chinewalker]

Re: 1978 evinrude 70HP driveshaft removal from lower unit

Gearcase bullet diameter would be smaller. Standard is about 4-inches. Small one is about 3.5.

Just as an FYI - if it IS a small gearcase with the 4-spline shaft, you could sell for enough to buy two or three standard lower units... They're kinda rare and sought after by the go-fast crowd.