Year mixture and prop questions

"I just bought a used 20hp mer

"I just bought a used 20hp merc. Ser#2188389 Stamped on the mounting area of the motor,(not like the picture on the website showing the tag on the side of the motor).
Not sure what year it is since the numbers seem to be less than the starting numbers for 1969 and greater than the ending numbers for '68. Any insight to what year it really is?

I ordered a manual for years '65-'89 but if anyone can tell me what the mix ratio is and what is the best oil to use, before the manual gets here that would be nice.
As a note, I did ask the previous owner what the mix was but he would only mumble something about using 3 quarters of a cup of oil to 5 gals and was going to look see if he could find the cup he used, but he kept wandering off into other things to say and it was starting to get dark....etc. Also does it make a difference whether you use premium or regular?

I haven't yet had the opportunity to run it on the water (won't until I get a gas mix..) but had it run by the seller and it started OK and idled fine, and it shifted into both forward and reverse OK. Noticed the prop has been filed a bit on two of the blades and it appears to be a tad irregular visually. Any recommendations as to whether the prop is going to cause any bad vibration?

So, I need a year
Gas mixture ratio
and insight on prop problems."

"Hi Joe,

- Interestingly,

"Hi Joe,

- Interestingly, my chart (downloaded from the European site of Merc's parent corporation, http://www.brunswickmarineemea.com/download/dosearch/@isnew/desc?mod=17&lang=EN& categories=Outboard$) lists that as a '67. But I understand that these numbers are not an exact science really. As long as you have the serial you'll be fine when ordering parts.

- Gas mix is 50:1 on any Merc dating 1966 and later (thanks, Graham L.). I don't think Regular vs. Premium should make a difference but I can't vouch for this since I live in Europe where the octane rating system is different (US guys please weigh in!). Any decent brand 2-stroke engine oil should be fine.

- re: the prop, AFAIK slight filing on the prop edges is standard practice, but any irregularity large enough to be seen is probably a no-no...

The more experienced outboard veterans on the forum can probably give you lots more specific advice."

"I get '67, 50:1 mixture,a

"I get '67, 50:1 mixture,and would cause vibration because if the balance is out it will not run true"

Thanks for the info.

Thanks for the info.

Got a new question for this mo

Got a new question for this motor. It won't swivel. I have it mounted on a saw horse and I can't turn the motor in either direction. Any solution other than to force it to move?

The swivel is froze up. You&#3

The swivel is froze up. You'll need lots of heat and regreasing to free it. Common problem.

Jeff

"I don't want to damage an

"I don't want to damage anything, where specifically do I apply the heat, and would that be with a torch?"

"Heat where the swivel is from

"Heat where the swivel is from top to bottom. A Benzomatic torch will do, though an oxyacetylene works far better.

Jeff"

"Thanks, that's much appre

"Thanks, that's much appreciated information. I'll give that a try."

"It takes a lot of heat and yo

"It takes a lot of heat and you must get fresh grease in while it is still hot to force the old grease out,other wise it will just seize up again, nice weather we're having."