Johnson 4R71D Resurrection Attempt

[Independent Thinker]

Hi All,
First post newbie here. Never owned or operated an outboard motor until now.
I stumbled across a 1971 4HP Johnson outboard for free. I'm not a mechanic, but I like fixing things and enjoy learning and the challenge of projects like this - within reason.

I need some help/advise on a couple of items (to start) and would greatly appreciate constructive feedback.

1. Does anyone know where I can find a shop manual for this unit? Free of course!

Motor is currently seized...Flywheel and prop won't budge...Pulled plugs still no go...Currently soaked cylinders for the last three (3) days with PB Blaster and Liquid Wrench...I haven't attempted to rotate the engine yet...

2. Does anyone here know how to get the head off without removing the engine from its lower housing? The bottom two head bolts seem too long and there doesn't appear to be enough clearance get them out with removing the engine from the housing. If my assumption is correct, how/what do I need to remove to get those bottom head bolts out?

current plan
Previous owner said the unit ran great when last used so I'm operating under the assumption that the rings are stuck to the cylinder walls...if/when I get the engine unseized, I'll check for compression and spark and make some decisions from there. What am I missing?
THANKS!

 

[racerone]

Just take the head off with the block in position.-----It will come off.----Then report on the condition of cylinders.

 

[kbait]

Pull gearcase to determine if it’s seized in gearcase or powerhead

 

[Crosbyman]

has suggested pull cyl head ...then soak the pistons/rings a few days with wd40 , or plain kerosene alternate tapping the pistons may loosed them up

use a one inch round peg and firm blows... not to hard ... alternate

resoak a few days if need be

if it clears up reinstall cyl head with a new gasket do the carb gear case oil water pump...

check ignition for strong sparks coils may be cracked and condensers bad....

 

[Independent Thinker]

Got it. Thanks for now guys!

 

[Independent Thinker]

Got it. Thanks for now guys!

Finally got a chance to work on the motor...Tried the head, removed 5 of the 6 bolts, then promptly sheared off the last one, so I tried the gearbox...No oil at all in the gearbox...A close inspection showed that the Gearcase Head Assembly had one of the "ears" that hold the bolts down was cracked causing a slight misalignment and pinching of an o-ring...maybe oil was lost through there? Did the previous owner drained it before storage? Not sure if that's something you'd normally do.

Everything is still stuck solid now...got three of the bolts from lower unit off...but not the fourth...scared to break that one too...used lots of PB blaster liquid wrench with tons of tapping...bolt is now stripped but I can get channel locks and vise grips on it. So I can't pull the driveshaft and see if the lower end turns...So really not much progress for 2 hours of work.
At this point, any ideas, along with encouragement could help. Ha Ha

 

[racerone]

Heat the exhaust housing to get that one bolt out.----Sounds like water in lower unit froze that will crack that housing.

 

[Independent Thinker]

Thanks for the comments racerone...I'm going to get a bernzomatic torch and see if I can get that bolt free and inspect.

 

[Independent Thinker]

Ok, got the lower unit off... Drive shaft came right out... Pistons move freely... Shaft still won't rotate prop....Gave up tonight when gearbox head screws and impeller housing screws were very tight. Any ideas where the gears or drive shaft tends to bind? Or what to look for. Thanks in advance for any all comments!

 

[Independent Thinker]

Hi all, thanks in advance for all the tips and advice so far...As you can see, got the lower end off...was able to take apart the gearbox and water pump in an effort to get the drive shaft to turn...still not able.

I'll tell the story with the photos L to R:
#1 This is what came out after removing the prop shaft.
#2 View of gearbox with the pinion gear at 9:00, drive shaft bearing in the middle, the nipple at 2:00 is I think, the oil drain.
#3 General condition of the prop shaft and gears...Cleaned up the gearing and spacer a bit (not shown) both are pitted. I haven't been able to get the gearcase housing, spacer off of the shaft yet.
Switch to water pump
#4, #5 L to R photos show (I hope you can see) what appears to be some damage to the lower end unit that houses the upper or driveshaft oil seal. I ran out of time but it almost looks like it the seal was tacked in place. I have to clean it up and inspect closer today.
I'm concerned with this and I wonder whether this that damaged oil seal "seat" has ruined the whole bottom half case.

I sprayed penetrating oil on the driveshaft and on the pinion gear last night to try to get it to turn today... Any advice, feedback or comments would be appreciated!!! Thanks

 

[racerone]

Somebody cracked the gear housing when replacing that seal.----Then used epoxy for a fix.----A used lower unit is what you are looking for.----Not hard to find in my opinion.----Your location ?

 

[Independent Thinker]

Somebody cracked the gear housing when replacing that seal.----Then used epoxy for a fix.----A used lower unit is what you are looking for.----Not hard to find in my opinion.----Your location ?

Thanks Racerone. Pittsburgh, PA

 

[Independent Thinker]

Hi Again, I realize that this thread is getting a little long, but I have a lot of questions. Taking racerone's advice, I think I can get a complete lower hlf for about $100.00. Not bad, but I really want to know



Hi All, more questions...

Taking racerone's advice, I think I can get a used lower 1/2 for this for about $100.00...that's not bad.
I checked the compression of the two cylinders with an AutoZone rental gauge...about 70 PSI on both cylinders...tested both a couple of times. I was going to test the ignition strength with a spark plug gap tester or something but I wanted to know from experienced folks if this compression level made this engine a rebuild candidate...or not worth putting money into it.
Thanks in advance for opinions...

 

[racerone]

It will run with 70 PSI.----You may be surprised how well it runs with that.-----$100 for a good used lower unit is a good deal.----Install a new impeller.

 

[Independent Thinker]

Thanks for the guidance again racerone.
Update: I haven't had time to work on the Johnson lately so that is why I haven't posted. I can get a lower unit for $100.00, but before I drive 3 hours and spend the money I was wondering what I should/could do before I go there. The bottom half will include a new impeller and changed gear oil.

I checked the ignition system. I'm getting good spark to both plugs. So I'll replace the old ones before start-up.
I was also planning to buy a carb rebuild kit and clean that up before I attempt starting.
What am I missing? I mean should I just repair or replace anything else proactively before I buy the lower half?
Thanks in advance for any comments/opinions!