Mercury 500 Thunderbolt 1970 50 hp gear case NO OIL

[Jbird12]

I have been reading threads from this forum for a while now and have been learning lots but im very new to boating other then being a passenger.

I am looking at buying a boat with a 50hp merc(1970. looked up the serial #). I looked at it today and checked the compression and got between 116 and 119 for all 4 cylinders. So i think she's good there. After that i went to check the gear case oil and i took out the vent screw then the drain screw but no oil came out. Nothing came out at all. The guy doesn't know much about the boat only owned it one year had it out once last year and it drove great he says. Im inclined to believe him and dont think hes trying to screw me but i dont understand why there was no oil in there? Are all the possible reason for that to be the case that arent deal breakers. I mean should i stay away if I dont know why theres no oil in the gear case? The motor looks like its in fantastic shape.

Any advice would be great. As i said Im new to this so maybe its something obvious.

 

[jerryjerry05]

Re: Mercury 500 Thunderbolt 1970 50 hp gear case NO OIL

Nothing at all???If it's sat for a while without oil then the rust probably has formed and you will probably need a lower soon.Fortunatly the parts are out there and the lower can be found.
Then again .Put some oil in it and go.It might last and then it might not.J

 

[Sunfish12]

Re: Mercury 500 Thunderbolt 1970 50 hp gear case NO OIL

The owner never drained it?Added to it? Only had it out ONCE. If you want it fill the lower unit and run it on the water then check for water in the lower unit before you buy it. It's still a risk.

 

[Jbird12]

Re: Mercury 500 Thunderbolt 1970 50 hp gear case NO OIL

Thanks guys, ya im going to try just filling her up and running it before i buy it. Ill have to wait a few weeks till the lakes clear up up here but ill post an update then.

 

[ajgraz]

Re: Mercury 500 Thunderbolt 1970 50 hp gear case NO OIL

After you run it, drain the LU lube and look for:
Foam/milky (water intrusion)
Silver flecks (metal shavings)
Black/reddish flecks (rust bits)

If you see any of that, either pass or lower your offer to compensate for needing a new LU.

 

[Mi duckdown]

Re: Mercury 500 Thunderbolt 1970 50 hp gear case NO OIL

Alot of people drain the the lower end in the winters to avoid any water what so ever.
Do really live in the Yukon?
that may be a common practice up there. .02
What scares me, is that he he ran it last year with no lube. It would not last an hour.??
Fill it up and try it. .02

 

[Jbird12]

Re: Mercury 500 Thunderbolt 1970 50 hp gear case NO OIL

Thanks guys yeah Im gunna fill it, run it, then check the lube after. Yeah I live in Whitehorse, Yukon but im in Edmonton, Alberta till May going to school and that is where the boat is.

 

[Jbird12]

Re: Mercury 500 Thunderbolt 1970 50 hp gear case NO OIL

So i filled her up gear lube and took her for a quick spin. Fired up like nothing and ran great. After though there was a little oil leaking out where the prop meets the lower leg. I got the boat for almost nothing so i let that slide. I am hoping i just need to replace some seals. I looked at the oil after and there was no gritty material in it so i think the gears are still good. So i guess im just looking for a little advice on what i need to do to stop the leak? Prop seal kit or something? And is it a do it yourself type thing? I am new to boats but don't mind doing stuff myself

 

[merc850]

Re: Mercury 500 Thunderbolt 1970 50 hp gear case NO OIL

Here are the lower unit diagrams


you should try to find a dealer that will undo the bearing carrier nut (2nd diagram Nr. 24) and pulling the bearing carrier may require heating and penetrating oil.