40 HP Johnson (40 75EL) Carb Rebuild

[livelyankee]

I just "rebuilt" the carburetor on my 1975 Johnson 40 HP Electric using the recommended repair kit for parts.

Several comments and a question:

1. The kit is only approximately correct. Wrong float bowl gasket, no packing for slow speed screw, poor instructions.
2 I have the factory manual. It is also poor on carburetor rebuild
3. Bought a new float which turned out to be completely wrong. Bad info in reference lists.

Possible I have a non-standard carburetor, of course.

COMMENT/Question: There is nothing for the slow speed screw to actually screw into,. ie no female threads. The packing nut has threads which engage matching threads in the carb. body but there's nothing for the slow speed screw to engage . Apparently it is intended that the packing material provide a sort of "thread" for the screw. Is this true, or has a previous owner lost a part? Particularly worrisome since this carburetor has a "lean-rich" control which provides about a quarter turn of adjustment via a thumb control on the engine cover. This works thru a plastic lever device which is simply pressed onto the splines on the end of the slow speed screw. Getting this thing in the right poisition without pulling the screw out of the packing is a delicate act and I fear it will fall apart in mid-lake.

 

[rickdb1boat]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

Any numbers on the carb? Should look like this:

 

[livelyankee]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

Sir:

TNX for your response. Your exploded view looks like the carb. Same general view appears as Fig 3-10 on page 3-5 of my manual.During disassembly I did not find a Bushing (item 6 in your view) which might be where the missing threads were. Possibly the bushing is still inside the slow speed screw bore.

The carburetor body has the number 379 486 and the additional notation "D2" The float bowl has the number 307777.

I believe that nmost of the choke let-off springs are also missing. None of them are shown in any of the exploded views or photographs but the bracketry & arms on the choke sure look like they were intended for springs. I don't see that they serve any purpose as they are, without springs!!

 

[Paul Moir]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

Bushing #6 does not normally come out as it is staked and pressed in place, but occasionally it does. It provides the threads for the low speed needle so if you're not threading into it, it must be missing. I assume it's not on the needle is it? It would be obvious since it's aluminium.

 

[livelyankee]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

Paul:

TNX for input. No, there was no bushing on the needle itself and no threads in the bore. Apparently an earlier "rebuilder" somehow has lost this part.

I can make another bushing but prefer not to bother. Any idea where I can buy a correct rebuild kit and/or this bushing? As of the moment the needle is "threaded" into the packing which may hold it provided nothing jars it. It is the original packing and quite worn & distorted---no replacement in the "kit" which I bought. For once in the saga of this snake-bit rehab project the ball has bounced in my favor inasmuch as I can work on the needle issues with the carb still mounted on the engine ie no need to wrassle the starter off again!!

I am beginning to get gun-shy about parts problems---too many wrong and/or missing pieces!!

 

[Paul Moir]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

I thought I had a spare one of these, but I can't seem to turn it up. The bushing (PN 303939) is listed as special order or end of use or something, so it may be trouble if the dealer has to order it. But a quick google of "303939 bushing" turns up a few places that have it, pretty cheap too.

It would probably arrive more quickly from them anyway.

 

[imported_Samuel]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

This is the same exploded view as the 40HP 40473 S , 1964 Evinrude Lark VI motor carb. I too found that none of the available kits matched and that they were in fact referencing what must be a none standard design. I also found that the 1967 Evin. 40HP motor uses this exact carb., also. In my rebuild I had to re-use most of the old parts as well...but it is running like a top. Nothing like a good disassemble and cleaning, even with the old parts. Good luck.

Sam

 

[Paul Moir]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

Which carb kits are you using?

From Bombardier:
439074 '60-'63, '71
439075 '64-70, '72-78

 

[livelyankee]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

Which carb kits are you using?

From Bombardier:
439074 '60-'63, '71
439075 '64-70, '72-78

 

[livelyankee]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

Paul:

TNX for bushung p/n. Please give me the number for the packing & washers because installing the bushing will require pulling the packing out a second time and I doubt it will survive in useable condition.

Can you suggest a good source for original Johnson parts for this aging beast?

The kit I used came from iBoats but I seem to have lost the invoice and packing list. It was apparently a universal kit because more than half the parts do not fit my carburetor and, as I say, many of the parts I needed are not there.

I agree with Samuel that a disassembly-clean usually improves running but I hate to reuse gaskets and packing. The labor to get the thing off the motor and back on again ( on an elecrtric start version) is too much to take shortcuts.

 

[Paul Moir]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

Lots of parts are available from your local dealer. If you're local dealer is no good, try theoutboardwizard.bizhosting.com or maxrules.com. Both are very helpful by accounts.

There's the aftermarket parts too that Iboats sells. Some of the aftermarket parts like ignition parts are very good but the carb kits aren't great.

Packing is P/N 307583 (18-7106), which any good dealer will have as it's common to many carbs. You can check part numbers yourself at:
http://epc.brp.com/default.aspx?brands=ej&lang=e

That friggin' bolt that holds the starter bracket on can be replaced with a socket head cap screw, which makes servicing it much easier.

 

[livelyankee]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

Paul:

Again, TNX!! I'll get after the Johnson dealers in my area first.

The engine does run---slightly off on low-speed mix but starts and gives me decent go at WOT so I am in a "go" condition. I like things right (deathly afraid of the dreaded "late on dark rainy night" problem) so will pursue this threads/packing issue.

livelyankee

 

[livelyankee]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

Paul: Got the "bushing" part (actually a type of nut) which provides the threads for the idle mix screw from a friendly but very expensive dealer ($15.47) so now carburetor is OK. However, the diode bridge is failed so need to replace it. The parts identifier site you cited above (epc.brp.com/default and so forth) doesn't work ---can you suggest a good site for parts identification? livelyankee

 

[Paul Moir]

Re: 40 HP Johnson (40 75EL) Carb Rebuild

I hope you get this livelyankee, PM seems to be busted for some reason.


That sure sounds like it's the problem. Surging is usually a sign of a fuel delivery problem. The engine slows down, consumes less gas, refills the carburetor and takes off again. Ignition problems are more like a sudden cut in and out. You go along at about half speed and then suddenly the engine comes to life and takes right off.
Water in the fuel sometimes does things like that too, but you would probably have seen evidence in the filter & tank.

The BRP site won't work because of Iboats' frame "wrapper". Click "Remove this Frame" in the black band at the top, then enter your email address.

I managed to find this pic on ebay:

Are the springs missing? Especially the one at the very bottom of the quadrant (really just a bent piece of stainless steel plate). #31 in rick's diagram. All the stuff on the other side of the carb is for the choke solenoid I believe.

Today I had an odd experience----the 40HP 1975 Johnson Electric started and was running well at good plaining speed. We made a gentle turn after about 5 minutes of operation and the engine began surging. It would slow down almost quiting, then accelerate up to almost full speed, drop back again and so on. I checked the water flow (fine), pu8mped the bulb (which seemed soft), vented the tank aand checked for gas leaks but nothing mattered. I stopped the engine, opened up the filter and found nothing. Started again and same problem. We took a brief lunch break and I discovered that the fuel line was underneath the (half full) 6 gallon tank. In other words the edge of the tank was pressing down on the fuel line. I pulled it out, and after our lunch,which took about 40 minutes, the engine seemd to run OK again--no surging and reaosnably steady idle.
Is it possible that the tank collapsed the line enough to restrict the fuel flow?

Another question---there seems to be no way to apply part choke. You either get full electric choke or nothing. he manual choke won&apst stay on except if I open the c over and jam it fully on right at the quadrant. I am certain there are springs missing from the choke linkae which would allow part-choke settings but nobosy seems to respond when I ask about this. The levers and so fort hin the choke linkage certainly look like they should have something attached to them.

Tom