1979 70hp choke

Ralph Porter

Cadet
Joined
Apr 4, 2017
Messages
7
Hi, I'm having some issues with my 1979 Johnson(70hp), starts ok but goes a bit wild, I don't understand the choke system, the key press activates the solenoid but there is also a lever next to the air box (label on air box is choke on / choke off) - what part does this play please? Also I cannot stop it once started, turning the key has no effect, i have to unplug the fuel hose! finally it's not spitting water, it has new impeller but i can only test with muffles on at the moment, does it need to be submerged? I'm a bit scared to start it again now since i can't stop it quickly and it's not pumping water, please help a novice in need!

Many Thanks

Ralph.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
The other choke is for manual operation and starting, if it works at the key you ignore it.

​There is a wire disconnected, corroded, or the switch isn't working correctly. I can't tell you color of the color of the wire, but someone here will soon.
 

175se

Petty Officer 1st Class
Joined
Mar 6, 2014
Messages
274
Black wire with yellow tracer is the kill(or shutdown) circut, could be pack or switch as#2 said.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Leave the manual choke in center or automatic position, use the push-to-choke key switch. You cannot test a water pump on muffs. But water should go through whether the pump works or not.
 

Ralph Porter

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Joined
Apr 4, 2017
Messages
7
Thanks folks, I don't think the manual choke has a center or auto position, just on or off, I assumed off was sensible but the motor was racing like crazy in idle until i dropped it to the on position, this makes no sense to me!
 

jakedaawg

Rear Admiral
Joined
Jun 26, 2012
Messages
4,275
The blk/yel wire needs to be put to ground to shut motor off. This is normally done by the kill switch. Do not put voltage to it.
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
36,047
When you pulled choke to " on "---It blocked off the air and motor was flooding with too much fuel.----That is why it slowed down.-----Find the reason for high idle speed.-----Ignition too far advanced ?---One off the THROTTLE plates open a bit ?-----Or hurry to a shop before you damage the motor !
 

Ralph Porter

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Joined
Apr 4, 2017
Messages
7
Well some progress thanks to you guys, yes severed black and yellow fixed, I can stop it now thank goodness. Idle adjusted and seems reasonable, shifts in and out of gear ok button still no water flowing (properly submerged now), I've already replaced the impeller... I'll take the gearbox off again and check it but how can I test the circuit before building it again? If I shove a hose up the spout would water flow to the tell tail with the engine off? Thinking if I can eliminate any blockage higher up then I can concentrate on the water pump and maybe replace the whole thing...

Again many thanks for you valuable help.
 

jakedaawg

Rear Admiral
Joined
Jun 26, 2012
Messages
4,275
When you repaired the blk yellow make sure you used a proper "crimp/solder/seal" water proof butt splice connector. wire nuts/hand twisted gizmos/blue plastic butt splices will not suffice and could cause issues.
 

David Young

Chief Petty Officer
Joined
Jul 12, 2015
Messages
485
Well some progress thanks to you guys, yes severed black and yellow fixed, I can stop it now thank goodness. Idle adjusted and seems reasonable, shifts in and out of gear ok button still no water flowing (properly submerged now), I've already replaced the impeller... I'll take the gearbox off again and check it but how can I test the circuit before building it again? If I shove a hose up the spout would water flow to the tell tail with the engine off? Thinking if I can eliminate any blockage higher up then I can concentrate on the water pump and maybe replace the whole thing...

Again many thanks for you valuable help.

​Make sure the long tube is going into the proper hole on the lower end. I would change the thermostat and the cork gasket. Also the poppit valves (2 of them), they are inside the thermostat cover. Get a new gasket for the thermostat cover too. You should get a 'factory' repair manual for your motor. I bought one for my motor for something like $38 and have saved myself over $1,000 by doing maintenance and repairs myself :)
 

Ralph Porter

Cadet
Joined
Apr 4, 2017
Messages
7
Sure thing, I reconnected the kill wire through the original sockets with some minor tweaks, sorted out the water flow as well, the impeller key was not catching sufficiently to hold the impeller in rotation.... All is well now bar some tuning to gear shift and idle, it idles ok but I'm not sure if it's correct since I have no experience of these motors, https://goo.gl/photos/sgnxcknUGgFFPRmX9 a link to a short video of it running, does it sound right I wonder ?

Thanks folks.
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
36,047
What was the part # of the impeller that you installed ?---Is it driven by a half moon key ?---Or a round pin ?----Or a plastic key ?
 

Ralph Porter

Cadet
Joined
Apr 4, 2017
Messages
7
437080 / 396725 It's a plastic graduated curve profile, long story but I bought this engine in pieces as a project, they was a new impeller supplied which I fitted initially however it was ridiculously tight in the casing I mean I could hardly bend the splines to fit in, when I did get it installed and it was all lubricated I could bearly turn the shaft using all my effort. I figured this was not as it should be so purchased a new impeller which yes took a little struggle to fit but spun with only minor resistance. I think somewhere along the path of my struggle the plastic key got rounded off a little and failed to play its part... Hope that makes sense.

Thanks,

Ralph.
 
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