1974 Johnson 40E74S -Couple of Q's

[eastcoast_btr]

Hey, just received a nice little 15ft Fiberglass boat from the father in law. Has a 40HP Johnson on it.

He was told at the last marina (as the guy was trying to buy it from him) that the motor had no "high speed". I had it out in a small bay and the engine started and ran fine. Not sure about top speed as I have little experience.

Took out the plugs and the lower cylinder looks well oiled, plug is pretty dirty, any chance that this cylinder is not running, the engine did sputter allot when I got back to the dock after a 20 min test run.

Last question, any one know the best fuel mixture ratio for this motor, I think the father in law was running it thick.

 

[F_R]

Re: 1974 Johnson 40E74S -Couple of Q's

Fuel mix is 50:1. Can't tell you if there is anything wrong with it or not. Disconnect and ground one plug wire and see how it runs. Then do the same with the orher plug wire. Should get equal results if it is running on all two. Also, a compression test will tell a lot.

 

[eastcoast_btr]

Re: 1974 Johnson 40E74S -Couple of Q's

Thanks.

Everything appears to run ok after my latest run, but it does have a hard time idling after a good run. Maybe I am expecting too much from a 34 year old 2 stroker. lol.

 

[tashasdaddy]

Re: 1974 Johnson 40E74S -Couple of Q's

this may help you. you have an adjustable low speed needle.

Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S 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 (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, 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.

 

[eastcoast_btr]

Re: 1974 Johnson 40E74S -Couple of Q's

Which screw is this? Would pictures help?

I did see some kind of "Initial Slow Speed Setting" under the cover on the labels.

Plus there is some sort of knob that turns half a turn and is connected to a lever that is connected to the carburator. This knob is right beside the choke.

Also there is something on the outside of the motor (on the rigid frame) that has three settings. Start/Fast/Slow, I do not know what this is about either.

Any one have an owner/service manual for this or similar model. Sorry for the greenery... my experience related to late model race bikes

 

[eastcoast_btr]

Re: 1974 Johnson 40E74S -Couple of Q's

Another Question...

How come when I hookup one of those rabbit ear water feeders (i dont know the proper name). I dont get any water coming out of the cooling outlet when the engine runs. (I dont keep it running obviously).

I have to remove a little cover on the side to hook it up, but it doenst seem to work correctly.

 

[JJags3]

Re: 1974 Johnson 40E74S -Couple of Q's

It is called a muff.

 

[eastcoast_btr]

Re: 1974 Johnson 40E74S -Couple of Q's

It is called a muff.

My muff doesn't seem to work then