Re: Help With Flushing A Vintage Mercury 850?
The first models took up water thru holes in the trim tab. Tempo used to make an adapter that wrapped around the water intake of old Big Twin Johnsons & Evinrudes and a similarly-styled flusher would work in your application.
However, don't know if they ever did make one specifically for the Mercs, and if they did, it'd be rarer than Hens Teeth.
There was a factory flushing adapter that screwed into the side of the lower unit on the Port side. You can see a large, slotted flushing plug to remove. But this is only to be used to flush the motor non-running. It puts water on the discharge side of the pump only and if you run the motor using this flusher you'll burn up the impeller.
Attached is a pic of a Tempo flusher used on Mercs which had an intake screen up underneath the rear of the lower unit. If you could find one of those, you might be able to bend it to fit the 'vee' of the trim tab and modify the foam to better route water to the intake holes.
Another pic shows the flusher used for old JohnnyRudes, borrowed from this old message thread:
http://forums.iboats.com/showthread.php?t=245821
Other than making your own flushing attachment or modifying an existing one, the easiest thing to do would be to pick up a used plastic water barrel, pickle barrel, etc and run the motor in that. Just make sure water level in the 'bucket' is well over the lower unit anti-ventilation plate. If you fill to around half-way up the exhaust tower, that's plenty.
You can even run it in gear at idle if you're careful. Just don't rev 'er up in the bucket or you'll get a quick, cold shower!
I've run hundreds of big outboards in the 'bucket' and it's a great way to put a bit of backpressure on the exhaust and get some load on the engine, idling in gear. This will let you tweak your idle mixture and speed way better than you ever could, running the motor on a flusher.
HTH...........ed
