Johnson Outboard

[allen29palms]

I recently aqquired a used Johnson, can anyone please decipher the Mod/#, S/# for me. <br />Model # FD-21R<br />S/N 12769377<br /> This motor was allegedly rebuilt, then sat baking in the Mohave Desert for the last 10 years, and I'd like to know what I'm getting into.

 

[JB]

Re: Johnson Outboard

Hi, Allen.<br /><br />Welcome to iboats. <br /><br />Your engine is a 1967. The dryness of the air there probably protected most metal parts.<br /><br />Squirt about a teaspoon of TC-W3 oil into each cylinder and let it soak for a day or so. Then do a compression check to see if you have stuck rings.<br /><br />Assuming good results there, replace the water pump impeller, clean and overhaul the carbs (gaskets will be dried up), clean and gap the plugs (Champion J4C gapped at .030) and give her a try.<br /><br />Let us know how you come out, and good luck

 

[allen29palms]

Re: Johnson Outboard

Thank You Kindly, I've already determined that the engine hasn't frozen, or suffered any internal corrosion. Fortunatley I have access to a borescope to look into the chambers. I've also pressurized the fuel system to leak check same. I realize it would be good medicine to rebuild the carb. I've just started looking into finding out more regarding servicing/parts/etc. If you could steer me towards finding a manual, of any technical info, I'd be forever indebted. By the way, this is obviously a 2-stroke motor, do you have any idea as to the gas/oil ratio? <br />Regards,<br /> Allen

 

[Paul Moir]

Re: Johnson Outboard

Fuel/Oil mix is 50:1 87 octane gas to TCW-3 rated outboard oil. Here's some additional info for you:<br />FD-21 1967 20hp outboard<br />Displacement: 22.0 CID (2.25" bore x 2.50" stroke)<br />WOT RPMS: 4500<br />Spark plug: Champion J6C (was J6J) gapped at .030"<br />Points gap: 0.020"<br />Lower unit oil: SAE 90W GL-5 outboard gear oil.<br /><br />Iboats offers many parts and aftermarket, Haynes like manuals. The OEM repair manuals, while expensive, are superior. Reprints are available from the following places:<br />TheOutboardWizard<br />Mastertech<br />Marine Engine<br />Ken Cook <br /><br />Try to get the carb rebuild kit from a Johnny/Rude dealer or here since they come with a replacement float. The 18- numbered aftermarket kit does not contain one. The old cork floats are known to de-varnish in modern gasoline.<br /><br />Good luck!

 

[allen29palms]

Re: Johnson Outboard

Thank God for the kindness of strangers!

 

[allen29palms]

Re: Johnson Outboard

Originally posted by JB:<br /> Hi, Allen.<br /><br />Welcome to iboats. <br /><br />Your engine is a 1967. The dryness of the air there probably protected most metal parts.<br /><br />Squirt about a teaspoon of TC-W3 oil into each cylinder and let it soak for a day or so. Then do a compression check to see if you have stuck rings.<br /><br />Assuming good results there, replace the water pump impeller, clean and overhaul the carbs (gaskets will be dried up), clean and gap the plugs (Champion J4C gapped at .030) and give her a try.<br /><br />Let us know how you come out, and good luck

 

[allen29palms]

Re: Johnson Outboard

Originally posted by JB:<br /> Hi, Allen.<br /><br />Welcome to iboats. <br /><br />Your engine is a 1967. The dryness of the air there probably protected most metal parts.<br /><br />Squirt about a teaspoon of TC-W3 oil into each cylinder and let it soak for a day or so. Then do a compression check to see if you have stuck rings.<br /><br />Assuming good results there, replace the water pump impeller, clean and overhaul the carbs (gaskets will be dried up), clean and gap the plugs (Champion J4C gapped at .030) and give her a try.<br /><br />Let us know how you come out, and good luck

 

[allen29palms]

Re: Johnson Outboard

JB:<br /> Thank You for you're sage advice. I've a quick question re: R & R of the pump impeller. Please bear with as while I've extensive experience with wrenching (USAF aircraft engineman,Military/Aerospace engineering)I've yet to tear into an outboard motor. Could I pester you for the reason(s) for replacing the impeller. It sounds like preventative maintenance. Is there something a greenhorn (as such) needs to know about this item (I.E made out of cheap degradable plastic,etc.? Thanks in advance for you're patience.<br /> Best Regards,<br /> Allen

 

[Paul Moir]

Re: Johnson Outboard

If JB doesn't mind, I think I can answer this one for you.<br />The water pump on an outboard is a combination positive displacement pump (self priming) and a centrifugal pump. This is done very simply by using a rubber pump impeller. A new one looks like this: <br />

<br />It is then scrunched into a housing like this: <br />

<br />The outboard's driveshaft runs through the centre of the impeller and drives it with the aid of a key or pin. As the rpms of the engine pick up, the arms of the rubber impeller bend over to the point where they no longer contact the sides of the housing. Then they act like the vanes on a centrifugal pump. <br /><br />Needless to say, the pump impeller wears over time, and if it's ever operated without water to lubricate it, it burns up quik. Also, if the impeller is kept in one position for years then it's vanes will take on a 'set' where some blades are bent hard over. Too often these impellers that have taken on a set fly apart when they're pressed back into service and clog up cooling passages in the engine.<br />The impeller ought to be replaced at least every two seasons. That way it's reliable - and you'll know that the lower unit will come off again next time it needs to be replaced since all the bolts will have been excersized.<br /><br />I hope this answers your question!

 

[allen29palms]

Re: Johnson Outboard

Once again, I'm indebted! I figured there was a method to the madness. Next phase will be procurring the manual/parts. I've got 3 foster kids breathing down my neck to go up to Big Bear Lake, and the little 12 foot Baycrest w/7.5 HP won't cut it. But I digress here. <br />Again, Thank You (All) Kindly! Anyone of you's guys are in 29 Palms, Ca. give a holler, I run the Best Western here at the home of the world's largest USMC base. (Hooyah)<br /> Allen

 

[allen29palms]

Re: Johnson Outboard

Good news/Bad news: I, thanks again to others, finished rebuilding the lower end, water pump, fuel pump, and carb. We took it to Big Bear lake and I spent about 1/2 hour "dialing-in" the carb. She worked like a charm for about 1.5 hours. Then after approx. 10 minutes spent idling/trolling, the engine started to develop a short duration, < than approx. .25 second, slamming sensation. It felt as if the boat had hit a log with the lower end. I've lots of experience with 4 cycle engines, and it somewhat feels as if the engine was backfiring into the cranckcae. I reopened the lower end just to make sure there wasn't a problem with the gear-train, I.E. the driveshaft gear rapidly engaging/disengaging the beveled drive gears. I tried to simulate the slamming by hitting the ignition kill switch. But the results where not nearly as intense as the slamming. Is it possible to have bad reed valves causing this sensation by misfiring into the crankcase. It's actually pronounced enough to worry about repetative slamming to damage the boats transom. A secondary observation was that unlike 4 cycle backfires, Lean mixture/extreme timing advance backfires out the intake, while rich backfires out the exhaust. I heard no noise of misfirng. It literally felt like the lower end pulsed dead for a split second then resumed power output thusly slamming the transom with reestablished torque reaction. Am I fulla it or what???<br /> Allen

 

[Paul Moir]

Re: Johnson Outboard

Bad news. That 'like hitting a log' describes a worn lower unit shift clutch dog. It's rapidly engaging and disengaging. Try holding the shift lever forward and see if that makes it stop.<br />You can try adjusting the shift lever detent points, but if that doesn't solve the problem then you're looking at a new clutch dog. Most commonly these are worn out by slowly engaging the engine in forward rather than slamming it into forward (as you ought to do) or sometimes from a misadjusted remote shifter.<br />Drain off your lower unit oil. What does it look like? Lots of sparkles? Have you got the proper lower unit oil in it? (it should be SAE 90W).

 

[allen29palms]

Re: Johnson Outboard

Thank You for you're quick response. I tore-apart the entire lower end, cleaned, and resealed same when I was going through the engine. I used the "Marine grade" 90 weight gearlube. I did try applying forward force on the shifter when it was running to no avail. I had though about this problem of jumping out-of-gear when it first started happening. I kind of assumed that I'd hear a bit of gear crashing as seems logical during this type of event. However I realize this sound may have been dampened by being under water, exhaust noise, and not the least, the sound of my going Ohh-_ _ _ _!, every time it happened. I will tear into the lower end here soon, and look for any signs of trauma, metal particles, et all. I did, when reassembling the lower-end, check the machined surfaces for any signs of wear, tear, slop, play, galling, or rounding of the dogs leading edges where they mesh with the forward/reverse bevel gears. I guess I'll just shut-up now and get on with what may be an autopsy. Again Sir, Thank You for you're guidance!!! Ps, Have you ever noticed just how worthless the factory shop manuals are at attention to detail? I guess that's why God invented "Old-Salts/Sages" such as yourselves.<br /> Allen

 

[Paul Moir]

Re: Johnson Outboard

Allen - <br />It's funny, but just about every time someone has a clutch dog problem here, they describe it as "like hitting a log".<br />Here's an idea - some of the clutch dogs have a direction to them. They'll have a grooved face to identify one end from the other. If you install it backwards, then it'll jump in and out of gear. Just mabey this is the problem.<br />Can you reproduce the problem in reverse?<br /><br />The OEM manual is the best of a sorry lot. I guess the later ones must be better the way some people go on about them. But at least they're generally right about most things, no matter how general.<br />It's the aftermarket manuals that irk me though. Here's a manual that was written some decades ago, has been reprinted countless times, and apparently has never been edited for even basic mistakes.<br />Thank goodness for Iboats.

 

[allen29palms]

Re: Johnson Outboard

Thanks Again,<br /> I did try running in reverse, and there was no indication of this problem. I tried even full throttle-ing to the point of plowing enough water to spilling over the transom. So you may have nailed it. I tried to be carefull when dis, and reassembling the drive shafts. I'll open her up and look for signs of apparent knuckle-headed-ness. I did have one minor question more if'n I could prevail upon you? Re: the prop shaft gearcase head: The reseal kit came with a standard metal-encased lip seal, while the outermost, as in the seal directly in front of the prop, seal in the OEM gearhead appears to be an internal o-ring seal, as the type you'd use a seal pick to remove from it's internal lands. Are there more than one design of OEM gearcase heads out there, with different seal configurations? I closely examined the head to see if it seperates for accessing this shaft seal, and I'll be damned if I can find a seam in the end of same!<br /> Thank You!!!!!<br /> Allen

 

[BF]

Re: Johnson Outboard

I don't have any help for you Allen, but it seems Paul has you well on the way. I've got a '70 25 hp (basically same motor as yours) that Paul helped me with earlier this season.<br /><br />Nice work Paul... I particularly like your explanation about impeller replacement, with pict's no less! It would look nice in "FAQ" section I think! (hint hint)<br /><br />Brent

 

[Birdup]

Re: Johnson Outboard

Allen,<br /><br />I had the same problem with my 1969 20hp. I replaced the clutch dog and it works great. I got mine from twin city outboards. They were reasonable and had fast shipping.

 

[allen29palms]

Re: Johnson Outboard

Thanks for the response, I found the problem with the leading edges of the ears on the clutch dogs. I had .080" milled off the faces to remove the damaged area. Bingo, I've got a great running outboard! I even tried it on a smaller 12 foot fiberglass boat, that now actually gets up on plane.