Logo
FULL SITE MENU

Automatic Choke Question

4

426hemi

Contributing Member
I have something of an Evinrude/Johnson Frankenstein. The engine was originally a 1963 Johnson 40HP with electric shift. At some point the lower end was replaced by the previous owner with a mechanical shift unit so the cut-out switch was removed. The power head is from a 1963 Evinrude Lark and is equipped with a water controlled automatic choke. Somewhere along the line the choke-to-cylinder hose was removed and the auto choke boss elbow in the cylinder head replaced with a screw in plug. The choke-to-exhaust-housing hose is still there but disconnected at the choke end and plugged. When I removed the plug from the hose a small amount of what appeared to be clear amber coloured oil dripped out. If possible, I would like to reactivate the water system to the choke so it is fully functional again and I would appreciate it if someone could help me with the following questions:

1. Would the elimination of the hoses to the choke be related to the change from electric to mechanical shift or is this just a coincidence? I don't see how they would be related but I also don't want to leave anything to chance.

2. What would be the danger, if any, in reconnecting the choke hoses? I have installed a new choke spring already.

3. Are there any other considerations that I should be aware of?

Thank you. :D
 
Is this a tiller model? If so, the PO may have changed the lower unit so he didn't have to have any electrical wiring for the shifter. The choke shouldn't have anything to do with the change to a manual gear case, he may have disconnected it because he was having trouble with it. Does the motor have any choke on it at all now?

What cut-out switch are you talking about? The vacuum cut-out switch?

I don't know a lot about the automatic chokes. None on my old motors have them. I don't believe there is any danger in reconnecting the hoses to the choke, but again, I don't know much about them.
 
You would have to make sure that the thermostat is properly installed as well.-----------No hot water then choke system will not work properly.----Start with running near boiling water through the choke " bimetallic spring " assembly and see what it does.
 
Thanks for the replies. I have installed a new thermostat and a new spring assembly in the choke housing so, other than reinstalling the choke hoses it is ready to go. I think I'll just hook them up and run a carefully monitored tank test to see what happens and report back.
 
All parts are either new or seem to be functioning properly. I understand that it is absolutely critical that the hoses are properly connected to avoid engine damage so I would appreciate it if someone could verify that I have things straight before I make the final connections and try it. In the pics below I have marked the four connections for reference.

As I understand it - A should be connected to B in pic called "Choke 1"

- C shown in "Choke 2" should be connected to D shown in "Choke 3"

Thanks.

Choke 1.jpgChoke 2.jpgChoke 3.jpg
 
When work was done on the choke you would have seen a diaphragm affair.----That is the choke pull off via the vacuum from the intake manifold.---------------2 fittings can be blown through and they are the water.----One fitting is for the vacuum pull-off and I do not believe you can blow through it.-----------Been a long time since I worked / tuned one of these up.-------In my area most of these motors have been discarded for newer technology.
 
racerone said:
When work was done on the choke you would have seen a diaphragm affair.----That is the choke pull off via the vacuum from the intake manifold.---------------2 fittings can be blown through and they are the water.----One fitting is for the vacuum pull-off and I do not believe you can blow through it.-----------Been a long time since I worked / tuned one of these up.-------In my area most of these motors have been discarded for newer technology.
Click to expand...

I thought about getting a newer motor but this will be installed on a fully restored 1963 Thompson Bros. Sea Coaster and I wanted to stay with the correct vintage. I'm going to follow all the above advice for testing before going ahead. I may just decide in the end to use the manual choke setting only. Thanks for all the input everyone!
 
UPDATE: I hooked C to B and routed a hose from D to a drilled outlet on the side of the engine providing a "tell tale" stream that these engines lacked. So far the automatic choke, cooling etc. all work like a charm during tank tests. Thanks again for all the help. You kept this amateur out of trouble.
 
Back
Top