1975 johnson 6hp starting problems

Gradywhite3535 · Jul 28, 2013

I had the engine running when I first got it about a month ago. Realized she needed a water pump and thermostat replacement. So took off lower unit and replaced the pump and thermostat. After i finally got the L/U back on i tried to start her up and it didnt start up. I checked for compression and spark and both were good( compression is low but similar to when I got it started earlier in the month). I'm thinking either fuel or ignition problems. My question is if theres spark is it worth taking flywheel off and inspecting whats going on under there. Could I have maybe loosened something or just needs to be cleaned up and adjusted. I remember when I started her up in the past i would have to have it at full throttle and then lower the Rpms down. Would that be a sign that there could be a ignition problem? FYI this engine means alot to me as its my grandfathers that passed away and I would love to get it running good. Also I'm a beginner but have been learning so much on this forum. Thanks everyone for all the help.

Daviet · Jul 28, 2013

Re: 1975 johnson 6hp starting problems

Installing a water pump should not have any affect on the starting of the engine.
What are the compression numbers?
Will the spark jump a 1/4" air gap and is it bright blue?
If you have to have the throttle that far open to start it, I would question if you have a link/synk or carb problem.

Gradywhite3535 · Jul 28, 2013

Re: 1975 johnson 6hp starting problems

The compression was 30 psi. Is there a link to sync carbs

nwcove · Jul 28, 2013

Re: 1975 johnson 6hp starting problems

at 30 psi you would be very lucky to get it to start. i would verify that number with a different compression tester and decide what to do from there. jmo

Gradywhite3535 · Jul 28, 2013

Re: 1975 johnson 6hp starting problems

Yeah I hear ya but like i said I already got it started before i started messing with things lol

Gradywhite3535 · Jul 28, 2013

Re: 1975 johnson 6hp starting problems

How do you sync the carbs or is here link on how to do it

pn · Jul 28, 2013

Re: 1975 johnson 6hp starting problems

just keep pullin till yer arm palls offf.

pn · Jul 28, 2013

Re: 1975 johnson 6hp starting problems

then spray seafoam down the carbs, hopefully that'll loosen something up to increase compression.

Gradywhite3535 · Jul 28, 2013

Re: 1975 johnson 6hp starting problems

Yeah I forgot I also took fuel pump apart and carbs. Maybe I didnt assemble the carb right or install it correct. I'm going to try and take carb apart and reassemble and see if that works. PN that is a good idea i will try n shoot some deadpan also. Would I have to lynx/sync a single carb and can anyone give me advice on how to do that

Tim Frank · Jul 28, 2013

Re: 1975 johnson 6hp starting problems

nwcove said:
at 30 psi you would be very lucky to get it to start. i would verify that number with a different compression tester and decide what to do from there. jmo

^^^ +1....deal with the compression.

the machinist · Jul 29, 2013

Re: 1975 johnson 6hp starting problems

Those fuel pumps are a bear to get everything back together right. There is one small spring internally that can fall over to the side when doing final assembly. Can you blow in the intake side & suck on the outlet side with it making a fluttering/vibrating sound? If not you have something together wrong.

Gradywhite3535 · Jul 30, 2013

Re: 1975 johnson 6hp starting problems

Yes I took apart fuel pump today and noticed the spring was hunched over and not straight. Does this'd prong have to be straight in order to work properly? Man that spring is hard to get straight BOY OH BOY lol. I will try blowing thru tomorrow. Thanks machinist. As you are probably the most knowledgable person with Johnson's, when i was taking apart the lower unit i was having a hard time installing the L/u and i layed the engine on the flywheel so i could try n make it easier(wow how stupid). Could"be that messed with anything? Thanks

Gradywhite3535 · Jul 31, 2013

Re: 1975 johnson 6hp starting problems

Does the spin have to be straight up or can it be tilted and hunch over a little bit?

the machinist · Jul 31, 2013

Re: 1975 johnson 6hp starting problems

If you smear a little dab of vaseline or chassis grease on the spring & plunger to hold them aligned as you reassemble. You did not loose the small white plastic plunger that goes on top of the spring did you?

Gradywhite3535 · Aug 1, 2013

Re: 1975 johnson 6hp starting problems

No it is still there but it did spring out of my hand and landed in the grass lol. Took me about 30 min to find. Thanks i appricate it.

geoffwga1 · Aug 1, 2013

Re: 1975 johnson 6hp starting problems

Just a quick tip.Put a tiny dab of Gorilla glue or similar on the lower end of the spring and put it in place and let it dry before you assemble.Careful not to use too much or you'll gum things up.

Gradywhite3535 · Aug 2, 2013

Re: 1975 johnson 6hp starting problems

Finally got her up and running again. The damn pump was installed the wrong way. When I took it apart and blew in it i didnt have the vibration you were talking about. Anyways i installed a new T stat and water pump. Should the water be coming out of this hole?

Gradywhite3535 · Aug 2, 2013

Re: 1975 johnson 6hp starting problems

Does anybody know of the water should be exiting this hole?

nwcove · Aug 2, 2013

Re: 1975 johnson 6hp starting problems

thats a drain hole, while running, water should exit the exhaust relief hole to the right of the drain hole in the pic....and it should come out with a bit of force. on a side note.....that motor isnt low enough in your barrel,, the water should be just below that hole as the pump wont self prime. lower the motor or raise the barrel!!!

Gradywhite3535 · Aug 2, 2013

Re: 1975 johnson 6hp starting problems

Ok good, the water was coming out with pressure, I'm not second guessing u but just for reference why does it have to be just below the hole?

1975 johnson 6hp starting problems

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