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Johnson 3hp JW-17c - A few questions

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FishyBC

Contributing Member
So I picked up a 1961 Johnson 3hp from my old boss. It was in surprisingly good condition.
I cleaned it up and put a little oil in the cylinders, dumped the old gas and put some 24:1 mix in it, pulled it over and nothing. Pulled and cleaned the carb, regapped the plugs and she fired up and runs.

Now to fine tuning. I'm going to replace the plugs with new J4C Champions but can't find what the gap should be anywhere.
Also, I replaced the packing nuts for the needle valves for the jets but they don't feel firm in their seats. First time with these old adjustments. What do I need to do to get them tighter ? The High speed isn't too bad but the low is wobbly.

If anyone knows of any information pages or service manuals, please advise. I found the one on ************ but it is pretty vague as it covers so many different motors.

Thanks for being such a great help !!
 
S/Plug gap is .030.......... point gap is .020

Pick up a few fiber packing washers (307583) from your local dealership so that the packing nuts will tighten up the needle valves.

(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle valve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, waiting for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
********************
 
Thank you Joe. The new plugs gapped correctly made a big difference. I did put 2 new packing nuts in (Sierra 18-7106) both the high speed and the low speed. Are those the same thing ? If so maybe I messed it up and need to pull it apart again and replace them again.

Also, I pulled the impeller out and in the process pulled the driveshaft up. it won't go back down now. It's riding up about an inch and doens't engage. Is there a trick to get it to drop back into where it's supposed to ? I've tried turning both the prop and the shaft but probably have just missed something.
Thanks.....
 
Well I'm half way there. I did find a post on how to get the drive shaft in and apparently those ones are tricky to get back in but if you lay it horizontally with the prop down, everything lines up and you can just turn the prop gently and the driveshaft and it pops right in.
These are sure cool motors. It has an aluminum water pump housing and brass fuel lines..... They really knew how to build stuff to last back in those days.

Off to get the carb working right.
 
So I think I am missing something when putting the needle valves back in the carb and putting it back together.
I think I have the order wrong. I am going to need to replace the packing washer on the slow speed again so hopefully I'll get it right this time.
What is the correct order for reassembly ? Those knobs for the needles are tough to tighten without changing the setting of the needle.
Any tips ?
 
FishyBC said:
So I think I am missing something when putting the needle valves back in the carb and putting it back together. I think I have the order wrong. I am going to need to replace the packing washer on the slow speed again so hopefully I'll get it right this time. What is the correct order for reassembly ? Those knobs for the needles are tough to tighten without changing the setting of the needle. Any tips ?
Click to expand...

When having the carburetor dismantled, I use a very small bladed screwdriver of which I have bent the very tip of it sideways. This crude tool allows me to insert it into the needle valve passageway to dig out the old deteriorating packing washers.

The factory part number of the packing washers is 307583.... Sierra's part number is 18-7106.

The design of the slow speed needle valve is quite different from the high speed needle valve and although they are easily inserted into either passageway... they are not interchangeable as to their location.

The slow speed needle valve has a long tapered and usually pointed snout... this is the TOP needle valve.

The high speed needle valve has a shorter length taper and usually the snout has the very tip of it flattened slightly. This is the bottom needle valve.

Adjusting the needle valves is the last step in the carburetor repairs as stated in my above reply post #2.

The carburetor requires four (4) needle valve packing washers, two (2) to a needle valve. The packing washers go into the passageway first, then the needle valve, then the locking nut. If desired, one can assemble the packing washers and the locking nut on the needle valve and insert the assembly into the passageway. The locking nut is to be tightened so that one can easily adjust the carburetor if needed BUT engine vibration will not be able to change the setting. DO NOT lock the packing lock nut down so that the needle valve is jammed solid!
 
That's great Joe. Thank you.
I think I get this part pretty clearly but the part I am struggling with is putting on the knobs at the end once it's all adjusted without it turning the needle valve as they flair out the needle valve sort of like the reverse of a Jam nut.
When I try to tighten them the needle moves and I can't just get it set and then screw it into place. Is there a trick to that ?
Thank you so much for your help.
 
Temporarily tighten the brass lock nut so that the needle valve can't move.

The screws should be special tapered screws that have a taper on the un-threaded portion of them and the needle valve's split end should be even with the edge of the knob hole that's facing you. The instant you start to tighten the screw that holds the knob on, that should jam the knob on the needle valve.

I can't understand why you're having that problem.
 
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