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Re-Assembly 6R72D Johnson 6 HP Powerhead to Casing

M

Mark-B-AZ

New member
Hi All. New here.
So I bought this old motor and took it apart to repair water pump and other odds and ends.
When I removed the powerhead from the exhaust casing some washer type stuff fell out.
Should have been more careful of course.
So I bought most of those parts new here and want to put it back together.
It isn't clear to me how to re-assemble this part to get those washers and parts in order on the drive shaft.
I had taken the lower unit off before I took the power head off the casing.
Any help getting this back together in the right way / right order is greatly appreciated.
Parts 1-6 in this diagram:
 
The diagram shows exactly how this mechanical seal is assembled.----Make sure the drive pin for this assembly is installed near the top of the driveshaft.-----First part to go on is the cup washer with the little bumps down.----Then the spring.----Then the carbon.----Then a new o-ring.-----Then the stator flat side down.----Then the gasket.
 
racerone said:
The diagram shows exactly how this mechanical seal is assembled.----Make sure the drive pin for this assembly is installed near the top of the driveshaft.-----First part to go on is the cup washer with the little bumps down.----Then the spring.----Then the carbon.----Then a new o-ring.-----Then the stator flat side down.----Then the gasket.
Click to expand...
I guess what I don't understand is how to put it together, not the order so much.
Do I mount the powerhead on the case first, then insert the lower unit / shaft with all these parts up into it?
 
Nope.----The lower unit is installed.----Then you carefully fit those parts.----Then install powerhead.-----Look closely and you will see that it is the only way to do it.
 
racerone said:
Nope.----The lower unit is installed.----Then you carefully fit those parts.----Then install powerhead.-----Look closely and you will see that it is the only way to do it.
Click to expand...
That does make sense to me.
I'm grateful for the info.
Better to do it once right.
When I dropped the lower the pin was cheered and I wasn't familiar with the motor.
Thanks!
 
The pin must come through a slot way up there in the exhaust housing.----Strong flashlight and look up there.----Common mistakes are made all the time!
 
Find the slot.----Position driveshaft , lining up the pin and assemble.----Turning the flywheel helps engage splines.
 
Well, I got the new impeller installed and the lower back into place.
Getting ready to mount the powerhead and ran into a big question.
I got a new gasket for this. But I see a gap where the frame meets the powerhead.
Looks like something might have gone there, but I have no idea.
You can see the little gap in these pics near the shift link. Any thoughts?
And also, do I need any kind of sealer or just the gasket?
Thanks!
 

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Just looked at 3 of 15 or more that I have.----Nothing goes in that gap.-----Assemble the motor.
 
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racerone said:
Just looked at 3 of 15 or more that I have.----Nothing goes in that gap.-----Assemble the motor.
Click to expand...
Good deal. Got the shaft and parts mounted and put together. Ready to mount. Now if I could only find those pesky bolts. :(
If anyone has photos and maybe measurements for those mounting bolts I'd be grateful. I can probably source them at Ace.
I made a pretty good search effort with no luck so far...

On the positive side I am learning a ton about parts bins, labeling parts, and taking lots of photos and notes on disassembly. ;|
 
Getting this thing back together and ran into another little issue. The pull start mechanism is kind of binding when I tighten down the two top retaining bolts. It seems pretty good if they are a bit loose. But the second they get tightened down it binds. Can anyone say what I need to replace or fix to make this smooth?
Thanks!
 
Just back them off a bit. I had that issue with one motor. I put a bit of blue loctite on the threads, with the bolts backed off just enough to prevent starter binding. No more issues.
 
That was the fix given to me by one of the most experienced members on this form, who worked as a service tech on those engines when they were new.
 
I wasn't quite comfortable with the loose bolt / loctite idea, although it is probably a perfectly viable solution.
So I found two small perhaps credit card thin or less washers and put them between the mount and the pull start.
Tightened it down and it seems to work perfectly.
I would still love to know if some bushing is worn or something like that causing the problem, or is it just a quality control issue.
Anyways, it seems to be pulling and rewinding perfectly so far.
 
All put back together. Haven't tried it yet. I need fuel.
One last thing that has me a bit concerned is compression.
One cylinder is about 58 and one is about 60.
I have rings for it, but didn't want to go that far unless necessary.
 
The bolt should not be “loose”, just unsnugged a wee bit. It’s only 1/4 turn or so from tightened. There is bushing top & bottom of the spool. Did you clean them & the ends of the spool that rotate in the bushings? (They run dry, no lube).
Try another comp gauge. Or try your gauge on something you know works, your lawn mower. If that also reads low, the gauge is bad. Those Amazon gauges are hit/miss
If it’s really 60psi, did you check the head gasket? The newer Sierra ones are better. Be sure to flatten the head, it will be warped. Search here for an easy free way to do it.
 
You could be right about the compression gauge. I have an old timer, and a new one from Napa that was a bit expensive. But it still looks like China made and not great. I'll try both and see if there is a difference.
I didn't check the head gasket. I guess I need to get that fuel and just try to start it up.
If it runs great I might call it a day and go fishing. If not, I guess I'll dig in deeper.
This whole motor was more or less a learning motor for me. I paid $200 for it, which is probably too much, because I've got another $200 in parts roughly. But not a big deal. I have learned a lot. Especially thanks to all the kind folks on this forum who are willing to take the time and give advice.
 
If the head has never been off it will be warped.----The original head gaskets were poop quality.----Replacement SIERRA is much better.----Great running motors if in good condition.
 
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