1965 Merc 500 --- Crack in Lower Unit...

[InMotion]

Hey Fella's,

I have a 1965 Merc 500 Short Shaft with a crack in the LU that is leaking bottom end oil out of it. Couple of questions:

- Would you advise stripping the guts out of the LU and having it welded?
- Can I take the LU guts, pickup a long shaft LU and swap the guts?
- Does anyone know of any other Merc models that the LU will work with? Example - Merc 650 or 1980 Merc 70hp?

Any other advice here is greatly appreciated --- new to the Merc world!!

Thanks,

IM

 

[Chinewalker]

Re: 1965 Merc 500 --- Crack in Lower Unit...

I am pretty sure the lowers from about 1964 to 1968 will work. Much later and studs start moving and the reverse lock changes...

Yes, the best way to have something welded would be to empty the housing. Make sure the welder knows what's going on, as the housing could warp which would make reassembly a bear...

 

[InMotion]

Re: 1965 Merc 500 --- Crack in Lower Unit...

I am pretty sure the lowers from about 1964 to 1968 will work. Much later and studs start moving and the reverse lock changes...

Yes, the best way to have something welded would be to empty the housing. Make sure the welder knows what's going on, as the housing could warp which would make reassembly a bear...

Thanks CW --- just trying to figure out the best route --- will a weld hold --- or is it just better to find a LU casing??? Not sure... new with this one!

Hopefully someone who has gone the weld route will chime in and share their experience --- for good or for bad!

Take care,

IM

 

[hotrod53]

Re: 1965 Merc 500 --- Crack in Lower Unit...

IMO, look for a used replacement, I don't think welding will be good although some people do it. Aluminum shrinks when its welded, your nut may not fit when you're done. There are good used units out there, I spent $140 on Ebay about 2.5 years ago for mine on my Merc 500, still working like a champ. It would be wise to buy from a used parts seller who pressure tested the unit. A used lower unit should hold 15 PSI.

With mine I needed to know how long the shaft was, how many spline were on the driveshaft, and does it have a preload pin on top. There are many that are interchangable. When you remove yours, look in the casting near the water pump, there will be a number like #1643-6037 that you can use to cross reference it. My replacement was #1643-6458 and it was the same thing.

 

[InMotion]

Re: 1965 Merc 500 --- Crack in Lower Unit...

IMO, look for a used replacement, I don't think welding will be good although some people do it. Aluminum shrinks when its welded, your nut may not fit when you're done. There are good used units out there, I spent $140 on Ebay about 2.5 years ago for mine on my Merc 500, still working like a champ. It would be wise to buy from a used parts seller who pressure tested the unit. A used lower unit should hold 15 PSI.

With mine I needed to know how long the shaft was, how many spline were on the driveshaft, and does it have a preload pin on top. There are many that are interchangable. When you remove yours, look in the casting near the water pump, there will be a number like #1643-6037 that you can use to cross reference it. My replacement was #1643-6458 and it was the same thing.

Thanks hotrod... I think I'm heading in that direction. After speaking with aluminum welder at work today, he strongly recommended to not weld as well. Cast alum is what he called dirty... meaning it contains impurities and as such will not weld well and will have a good chance of cracking later.

Great input. Thank you.

Im