How else can you find out the model number?

[eavega]

So, I have just acquired another Johnson outboard. Traded my 10 HP for what is supposed to be a 20 HP. Now the guy who traded it to me bought it from someone else, and that someone else painted the entire motor black, including the plate with the model number on it. I cannot make out any kind of model number on it. I tried using heat to see if I could maybe cause the paint to bubble, but no avail. I don't want to use any kind of abrasive to strip the paint, since that would probably strip off the numbers on the plate, too. The only marking on the powerhead (other than the part numbers for various parts) is the a number stamped on the freeze plug - J2894796, which looks more like a serial number to me.

Best I can tell, its gotta be 1969-1973, since thats the only years since 1950 that Johnson was making a 20 HP.

Apart from parts, I also wanted to get manuals, service guide, etc, but don't want to order the wrong thing.

Any help would be appreciated.

Rgds

Eric

 

[tashasdaddy]

Re: How else can you find out the model number?

call a dealer see if they can crossreference the serial number.

 

[F_R]

Re: How else can you find out the model number?

I have a limited list of serial numbers that I have collected. 2,882,047 is a 1968, so I suspect yours is a '69. Close enough for a service manual anyway. They didn't make any real changes till about '72 and by then the serial numbers were up into the 3,6xx,xxx range.

 

[eavega]

Re: How else can you find out the model number?

Thanks guys.

Local dealer suggested to look through the exploded parts diagram, and try to find differences. Also suggested paint thinner should take the paint off, with the added bonus that if the plate is engraved (he said some years the model numbers were not stamped in, just printed), the paint remaining should really bring out the numbers.

I called back the guy I got the motor from this morning, and he told me that the guy he bought it from told him that it was a 1970. Based on that and some very subtle differences between some of the parts for the 1969 20 HP (20R69B) versus the 1970 20 HP (20R70C) (Came down to the choke lever and the low-speed adjust knob ), I am going to go with the 20R70C until I can prove myself wrong.

So, that having been said, and with my maintenance guide and owners manual on order, can you guys tell me what is the fuel mix for this motor? I used 24:1 for my 10 HP, and needed to know if I should continue to use that mix for this one, or move to 50:1?

One more question; The guy I got the motor from told me that it was hard-starting and would run rough, and he didn't have time to mess with it anymore, he just wanted a working motor. He had paid someone to do maintenance on it, which he told me included having the carb cleaned and rebuilt, impeller replaced, and LU oil replaced. The guy he had work on his motor told him that the reason it was running rough was the ignition system, so coils, points, condensers, etc. This was "diagnosed" without pulling the flywheel. now when I opened up the motor he had some Autolite 303 plugs in the motor, gapped at roughly .040. (they actually had some spot rust on them) About the only thing I can definitely see on the motor is the starting instructions and spark plug information label on the inside of the engine cover, and it says J4J plugs. Do you think that these plugs might be the cause of the hard start/rough running? Should I install the correct plugs and try to start it, Or is the safer course to pop the flywheel and check all the ignition stuff underneath? I've already checked compression and its "decent" at 95#, and dead-on equal. I also checked for a spark with the new plugs, and I get a spark. It is blue-white, but I don't know if I would term it "thick".

-Eric

 

[F_R]

Re: How else can you find out the model number?

Spark plugs should be J4C (replaces J4J), gapped at .030". I don't know what the Auto-Lite equal is. The .040 gap is reason enough for hard starting. Fuel mix is 50:1
You are checking the spark by laying the plugs up against the block and cranking it over? That is not a spark test. They need to jump a 1/4" gap in open air. If it will do that, don't worry about the thickness or color.

 

[eavega]

Re: How else can you find out the model number?

You are checking the spark by laying the plugs up against the block and cranking it over?

Kind of...I take the plug, use a rubber grip-clamp to hold the plug a distance from the block, then crank. The spark plug is definitely not right up against the block. I did see a spark, and it jumped from the plug to the block. I didn't measure precisely 1/4", but I would say it was in that ballpark.

-E

 

[eavega]

Re: How else can you find out the model number?

Not to revive this thread, but I finally found out what the motor was. Its an FD-22 - 1968 20 HP. I base that on the exploded diagrams on the Johnson website. When tearing into the motor I found that the air silencer plate is different between the 68 and the 69->73 models, and that after the 68 model, all the rest came with a flywheel with non-removable starter gear ring. since the Johnson website only goes back to 68, I am going to have to assume that it is a 68 (although, given the info that F_R posted earlier regarding serial numbers, I think its a safe assumption)

This kinda stinks b/c I was told by the guy I bought it from it was a 1970 motor, and based on that I have already ordered parts and a service manual. Also, I had a guy I know give me an old seized up 1973 25 HP, which shares a lot of parts with the 20 HP, but less with the older models than the newer models.

Anyway, thanks for all the help above. I tried to start it a couple of days ago in a tank with the correct plugs with no success. I popped the flywheel and saw a frayed wire off one of the coils, so since I had the flywheel off already I have ordered the coils and full tune-up kit, so I am going to start there.

-Eric

 

[ftltony]

Re: How else can you find out the model number?

Sounds like we need pics to go along with this post because it is getting interesting! Let us know how you do!