Mystery Mercury lightning 2

Hi all, I have joined the outboard community by purchasing an outboard I can tinker with to get gear on my hands before investing in something else however I am to have stumbled on a mercury outboard I can find no information online and no serial number.... May be a very very old model the cover needs to be unscrewed to pop off?!

Have so far removed and cleaned the carb, replaced the plug and put in new fuel and oil and seems to stall when I put it on mac revs. Wondering if it's overheating as it does feel very hard to pull when it happens!

Any clever ideas?

 

Is it water cooled? If so does the water on exit feel hot?

 

It is, when I ran it fast it did actually feel quite hot. As water was actually going out (mostly from the top hole in the stem and not so much from the hole under the engine block) wasn't sure if the impeller needed looking at? Do these old models have a thermostat too?

 

Welcome to the forum.

Yep, the impeller should have been checked (replaced) before attempting to start her and if it's seen any time (seconds) without having the pump inlet immersed, it's cooked and needs replacement now. The very first part you should buy for this engine (it does have a serial no.) is the repair manual.

This will show you where to find the serial number and how to diagnose issues and replace parts. Your engine is mid 1970's.

 

Hi Par that is helpful. The engine was not started out of the water but guess you never know the state of the impeller... Just hoping the engine block is not completley caked.
Bought the book and will disassemble the leg to have a look... Still can't find any serial numbers tho!

 

It's not necessary to disassemble anything. Only the leg needs to be removed (just a few bolts) and it drops off. Raw water impeller are considered "consumable" items and should be replaced as part of an annual maintenance routine. It's very probable the cooling system needs to be well cleaned. Bigs and critter love to climb up and make a comfortable home for themselves, reducing if not stopping flow. Additionally the thermostat may be stuck, bits and pieces of previous impellers may be wedged into the passages, etc. Simply put, lots of things can make it run hotter than normal. It's not uncommon on these small engines, to have floating debris plug up passages, so I usually back blow the passages with air from the "pee" orifice, to help clear things out, of course with the thermostat removed.

On a new acquisition, I generally like to start from a clean slate, so I'll boil out the coolant passages, replace consumables, like gaskets, thermostats, filters, hoses and clamps, etc. This way you know what you have, when it was installed, the condition of surrounding bits and pieces, etc., so any new "issues" will likely not be an old filter or leaking hose end or something that was already dealt with, just after purchase.

 

Some small motors carry the Mercury brand, but were built by Japanese makers. Which may be a good thing, the bigger engines in the stable were renowned for corrosion prior to 1984.