1965 650 lower unit

[Billwoot]

So this winter cracked my lower unit long story short. I believe I have a 1965 650. I cannot seem to find much information on the motor/lower unit. Serial number for the motor is1845956. The lower unit I took off was part number 1623-2460. I found a guy selling lower units locally so I purchased them all looking similar but not the same p/n. So one was number 1623-4021 this is the closest match from what I can see I have. The other two have the p/n 1623-2022. Will any of these fit my motor? Also I may be able to weld the original and avoid this whole mess. Let me know what you guys think and I’ll weigh the options. Thanks in advance, and let me know if you need any more information.

 

[racerone]

if there was water in the lower unit the gears and bearings may be bad.---Take it apart for inspection first.

 

[Billwoot]

Yes, I took the original lower unit all apart. The gears look great nice and bright with no visible wear to them at all. I’m guessing that the bearings are a different story but they could be good as well as there was a good amount of oil still in the case. The new lower units are all complete but I figured I could swap whatever I needed or get replacement parts. Upon further inspection the 2022 cases are from 1965 650’s but have different part numbers and they physical looks of them are different.

 

[Faztbullet]

Check the gear ratios.....rotate the driveshaft and count how many turn it take to make prop turn 1 full revolution.

 

[Billwoot]

2022 is two turns of the driveshaft one full rotation of the prop.

measured shaft length. Original was 18” all others are 22.5”. As soon as I get to my computer I’ll upload a few pictures.

 

[Billwoot]

So the first two pictures are the 2022


The second two are the 4021. This one has the more similar looking housing. Have not been able to find out what its off of. Im thinking a later model.

The one with the water tube and shorter shaft is the original lower unit.

 

[Faztbullet]

That's a 2:1 ratio and will make motor a dog if you ski/tube...will kill holeshot and you will need to change prop pitch.

 

[Billwoot]

I do believe that is what was in the original. Don’t do much of that kind of stuff or more of a fishing and cruising vessel. Should I just be able to change the shafts out?

 

[Faztbullet]

Original should be 2:33 to 1

 

[Billwoot]

Original should be 2:33 to 1

so best bet is to reuse original gears and put in new bearings and seals into the other casing?

 

[Faztbullet]

Driveshafts wont interchange in housings as yours uses a roller bearing and the other uses a cone bearing(preload pin)..Housings are machined different....

 

[DeepCMark58A]

Save the drive shaft off the original lower unit, that part alone is worth more than $100 on the resale market.

 

[Billwoot]

1623-2022 did swap out with no problems. Just pulled it all apart and changed the shafts. Pretty straight forward for anyone else looking to do this. Did not notice a loss of power actually seems to run better now.