Older mercury 1978 thunder bolt 50 hp

[tgpfloat]

My lower unit leaks bad. Was told by my local dealer that the prop shaft and drive shaft get pitted over time because they are not stainless steel. Because shafts are pited they canot be re sealed or you can re seal but the lower end will still leak. When did mercury stat using stainless steel in their lower ends? Options?
I have found a replacement lower end at a marine junknyard for $500 but won't I have the same issue with the replacement lower unit? I have heard that other companies used stainless steel in the lower units may back into the sixties should I want to replace this motor Thanks for the help

 

[Toddboat]

Re: Older mercury 1978 thunder bolt 50 hp

Rather than buy replacement lower units that may have the same problem, why not do some research on what product could be used to seal the pits? It's only around the circumference of the oil seals that needs to be filled. Oil seals are usually installed with marine grease, but in your case you may need something with some adherence. When I removed my oil seal on the propshaft recently, it was completely stuck to the housing. Maybe you can replicate this. I'd hate to tell you the wrong thing, so you need to research a product yourself, but I'm thinking something along the lines of 100% silicone or PL Premium construction adhesive.

 

[carholme]

Re: Older mercury 1978 thunder bolt 50 hp

Firstly, where is it leaking from?

Gerry

 

[Chris1956]

Re: Older mercury 1978 thunder bolt 50 hp

My '77 Merc has a stainless steel drive and propshaft. The '73 Mercs had a steel driveshaft and SS propshaft. I suspect your dealer is confused. The propshaft seal is complicated to replace. The driveshaft seal is easy to replace. Just replace the waterpump base, as it is installed in the pump base. use new gaskets on the gearcase plugs.

Where is it leaking from? Are you sure it is gear oil and not 2 cycle oil?

 

[Chris1956]

Re: Older mercury 1978 thunder bolt 50 hp

They also sell Speedi-sleeves to repair the sealing surface. I have never tried one.