big twin carb/choke?

[Robert Ellis]

Hi, I’m currently working on some late 60’s evinrude/Johnson 33 hp and 40 hp motors. Most appear to have the same carb system. My question has to do with the choke assembly. It appears to be some sort of combination of manual lever, electric and possibly (I’m not sure about this) hot air input? This hot air?/electric part of the choke goes into a housing located on the starboard side of the carb. This housing has a round cap that is attached by 3 screws.
Ok, the motor I want to test (1968 40hp evinrude 40852 D) has that carb arrangement except that the cap and screws are missing and looking inside, the various cams, cables etc. are not attached together so it couldn’t possibly work even if I had the cap. That’s ok, I have no problem using a manual choke. I’m reluctant to start it however without knowing what is going to come out of that copper tube which I’m guessing delivers hot air. My question is, Can I remove that copper tube where it exits the motor (3/4 of the way up the motor, near the back, on the starboard side, under a little heat shield type thing) and simply plug that port? Any advice/suggestions would be greatly appreciated!

 

[F_R]

OK, you are pretty correct in your analysis. There is an electric choke, activated by a switch on the control or dash. That closes the choke for cold start-up. Then there is a second system, a bi-metal spring coil that partially closes the choke after it is running, during the warm-up period. That bi-metal spring is part of the cover, and is heated by hot air drawn through the tube. Air enters a fitting in the exhaust cover below the one for the tube, passes through a heat exchanger in the exhaust area, through the tube to the carburetor, then into the intake manifold. When warm enough, the choke will be completely open.

If your electric choke works and closes, there probably is nothing wrong in the housing. The stuff isn't supposed to be all connected together. As I said, the bi-metal is part of the cover. So hopefully all you need is get the parts and put them on.

Part number 379539 cover and bi-metal spring assy
310383 gasket
310476 screw (3)

Yes, you can forget the whole thing and leave it as it is if you don't mind the way it works now. No need to remove the tube or plug anything.

Disclaimer: If the heat exchanger is burned out, it will draw exhaust gasses into the choke/carburetor. That may be why somebody removed the parts. If that is the case and you don't want to replace it, you should plug both holes leading to the heat exchanger to prevent exhaust gasses from blowing under the hood.

 

[Robert Ellis]

ok thanks F_R. The wire to the electric choke has been cut (annoyingly, right at the housing) and the other end (if I remember rightly, there's a little spring and stuff) isn't attached in any way to choke shaft) so I can't see it doing very much. So ... I guess I'll test the motor in the tank this afternoon with the manual choke lever (new ignition - flywheel back on clean and dry ha ha) and keep an eye on that housing for any sign of exhaust gases. I like to do the first start with the hood on though in case of flying projectiles - it would be just like me to leave a socket or bolt or something on the flywheel! lol

 

[Robert Ellis]

Just to correct a statement in my original post. None of the 33 hp motors I have use this carb arrangement.

 

[F_R]

Nope, that choke was only used on the 40hp and in modified version on v-4s

 

[Robert Ellis]

Ok .... took it to the lake and fired it up with the hood on but the manual choke door open. The was some blue smoke in the engine compartment. Ran it for 5 mins or so at a fast idle then shut it down and took the hood off and restarted it. I couldn't see any smoke coming out the copper tube so I assume the smoke I originally saw was from various cleaning and oiling operations I had performed earlier. Put the cover back on and took her out for a good run. Runs very well at all speeds and upon return to the dock - I opened the choke hatch and no smoke whatsoever ... I guess she's good to go as long as using the manual choke is not too onerous.

One thing I did notice that isn't great is that the hot air/electric choke housing is loose and wobbles about a bit against the carb. It attaches to the carb body with 3 screws but oddly I couldn't tighten them? I'm thinking the most straightforward thing to do would be to simply remove the housing. The trouble with that is I can't quite figure how to get the little lever (the spring in the cover probably engages with this lever) that is attached to the choke shaft. Any ideas on how that lever comes off? I Don't want to start prying things that I don't know anything about. I guess if worst comes to worse, I can somehow fit a little wedge to keep the housing rattling to a minimum.

On another note, I have a bunch of unrelated questions (some general, some specific to these 40 hp motors) do I need to start a new topic for each one or is it ok to open a topic with a bunch of unrelated questions?

 

[HighTrim]

I would open a thread with all questions to that motor! I cannot seem to envision what you are having trouble getting off.

 

[F_R]

The arm/lever does not come off the choke shaft. Furthermore, you don't want to remove the two screws that hold the choke plate on the shaft. That will destroy the shaft.

http://s19.postimg.org/d71zj0prn/6_Carburetor.jpg

 

[Robert Ellis]

Ok, great diagram ... thanks, glad I asked before trying to pry it off lol. It must be screw #49 (I think there are 3 of them – I’ll look again) that will not tighten the housing to the carb. It’s not stripped, it just won’t go in any further. What is part #46 – does it go between the choke housing and the carb? I’ll print this diagram out and have a closer look at the carb. It doesn’t help that the inside of the choke housing is very black – presumably from the hot air tube.

 

[F_R]

#46 is a gasket between the choke housing and carburetor. If might be destroyed by the housing vibrating and shaking around.

 

[Robert Ellis]

Just had a closer look - that gasket is definitely not there. Maybe that explains why the 3 screws won't pull to housing up to the carb! So ...I'm thinking of backing those screws off a bit and wedging something in between the housing and the carb (in 3 or so spots ... a phoney gasket if you will) and then tightening the screws up to lock those wedges in place and hopefully stop all the housing shaking. Any thoughts about what I could use as the spacers. I guess it's well in front of the motor itself so high heat shouldn't be an issue. I don't think cardboard would be durable enough somehow lol.

I was thinking that if I connected a water pump up to that heat exchanger circuit, I could serve hot tea on board ha ha