Merc Thunderbolt 50 - what year? And prop?

[coastal hermit]

Just got my very old, long stored back-up motor out of the back of the garage. Picked it up as ' insurance' in case my Honda crapped out. And it did. This motor is old! Serial number 7052334. What year is that? Roughly? I am guessing mid 70's? And the prop seems kinda small. Shouldn't this puppy turn a bigger wheel? There is room for another inch in diameter. And the boat is light. Got spark. Got 140-130-140 in the top 3 cylinders and 'thumb-feel- indicates similar for the bottom. I was just gonna add fuel and fire her up but - well, all this time........I am a bit leary.........

 

[carholme]

Re: Merc Thunderbolt 50 - what year? And prop?

That s/n comes up as a Canadian built engine:

50 1975 EL 4141000 - 4357639 7051983

From here:

http://www.maxrules.com/models/Merc_model_files/40-50.html

Parts listing:

http://www.crowleymarine.com/mercury-outboard/471.cfm

Old???? My '68 is as strong as the day it was built and I am just finishing a '66. They are bullet proof if looked after. If it has been sitting that long, I would renew the impeller, fuel pump, at least clean the carbs, new oil in the LU and give her a nice gentle run for a few hours and see what you have.



Gerry

 

[coastal hermit]

Re: Merc Thunderbolt 50 - what year? And prop?

Thanks, Gerry. It is, indeed, Canadian built. As am I. Produced in 1948 in a bad run full of lemons, if you must know. The motor is 1975...? That would have been my guess..roughly. So, thanks. What do you think of the 'prop' question? Did people 'prop' up a bit on those motors. There is room......... By the way, without looking it up, I can only see one screw hed on the leg. It is above the lower, lower hub and suggest the it is the 'filler'. But then I can't find a 'drain'. So, I am confused again (I told you I came from a bad run)

 

[carholme]

Re: Merc Thunderbolt 50 - what year? And prop?

http://www.crowleymarine.com/mercury-outboard/parts/471_19.cfm

See items 31/33, screws, upper is Vent and lower is Fill/Drain. Fill from the lower one with the top opn and when oil reaches the top, you are full. When full, put the top one in first which will hold the oil in for you while you remove the pump and install the bottom screw. Always replace the seals whenever you have the screws removed. You can find excellent little pumps which fit the oil bottle at Cd. Tire for about $12.00.

What size prop do you have on now. Both of mine are 10.75X11. You should be able to see numbers on your prop.

The service manual for that engine is P/N: 90-75512

http://www.chrysleroutboards.com/more_service_manuals.htm

This is a decent price for a manual. Watch out for those guys on Ebay as they know people are looking for manuals and they have them priced as much as a new one from Merc.

To get you started, here is a link to the condensed version of the Clymer manual. Ler the page load for several seconds and download soonest to your computer as the link is short lived.

http://web.ebscohost.com/serrc/pdf?...f-957c-802e69146c29@sessionmgr14&vid=4&hid=12

Gerry

 

[merc850]

Re: Merc Thunderbolt 50 - what year? And prop?

The only way to prop the motor is by using a tach to find out whether you are in the max RPM range (4800-5500) and what you need to do to reach it. With one person onboard you should aim for the hi end.

 

[coastal hermit]

Re: Merc Thunderbolt 50 - what year? And prop?

Thanks, guys. But my browser wouldn't let me access any of those links??? No idea why. And I can find a lot of old 'exploded views' of the Merc 50 but I can't seem to find the two screws!! This is a 1975 Mercury 50 Thunderbolt. Serial # 7052344. This is so exasperating, I even had my wife search the parts lists and the pictures. Now that is desperate! I don't get it. What do they call these screws? I can find one that says 'drain screw' so you'd think the other would say 'fill screw'. But no! I can only find the one. That is crazy. Is the damn thing so high up on th eeg that it is near the engine?

By the way................the impellor...........if the hole is pissing, do I really have to go in and inspect?

 

[merc850]

Re: Merc Thunderbolt 50 - what year? And prop?

Here's a page from the Merc manual that shows the location of the screws, there is also a FLUSH screw but that is not a lube point, - you undo them both to drain and fill the LU. You can buy a pump at a dealer for filling and I would recommend Quicksilver gear lube, you put the fitting into the LOWER hole then pump lube until it comes out the top, then replace the top screw and next the lower. The impeller should be changed due to its age and unknown condition.

 

[coastal hermit]

Re: Merc Thunderbolt 50 - what year? And prop?

No fool like an old fool, eh? I kept lookin' and lookin' but didn't see it. NOT wearing my glasses was part of it. But the other part was that whatever fool owner there was ahead of me had painted over it! Did such a good job I had to just 'poke' where it should have been and it was revealed. Stupid. Both of us! Anyway, the motor seems OK visually. Clean. All the parts in the right places. NO duct tape. But, after checking all fluids and spark, I am getting nada. Feels like fuel. Sounds like fuel. Probably fuel. So, I guess the carbs come off and get cleaned. Then I'll try again. And you guys find this fun?