1983 Johnson 75hp, completely out of ideas.

[kodibass]

Re: 1983 Johnson 75hp, completely out of ideas.

Have you tried running the engine while dark? I have found arching problems on 2 different outboards by doing so, one was just slightly visible even at night,

 

[Haffiman]

Re: 1983 Johnson 75hp, completely out of ideas.

Time to be a bit 'unconventional'.
1: Mark TDC of all cyls at the flywheel and test that you have spark for each cyl at correct time and only one cyl fires at the time.
2: 'Borrow' a 4-stroke carb synch tool ( http://suzukidave.myphotos.cc/suzukidave/Suzuki Tech/Carb sync tool.jpg )
check that you have the same 'vacuum' at each carb when running at idle and plates closed. This will give you an idea about the crank case 'compression' in your engine as well as leaking/defective reeds. (defective reeds the 'floater' will jump up and down with each stroke due to blow-back). Un-balanced crank case compression will have, particularly at idle, same effect as low compression on full speed - lack of power.

PS: I take for granted that you have checked thermostat and temp??

 

[AEROCOOK]

Re: 1983 Johnson 75hp, completely out of ideas.

What was your carb cleaning procedure?

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

Time to be a bit 'unconventional'.
1: Mark TDC of all cyls at the flywheel and test that you have spark for each cyl at correct time and only one cyl fires at the time.
2: 'Borrow' a 4-stroke carb synch tool ( http://suzukidave.myphotos.cc/suzukidave/Suzuki Tech/Carb sync tool.jpg )
check that you have the same 'vacuum' at each carb when running at idle and plates closed. This will give you an idea about the crank case 'compression' in your engine as well as leaking/defective reeds. (defective reeds the 'floater' will jump up and down with each stroke due to blow-back). Un-balanced crank case compression will have, particularly at idle, same effect as low compression on full speed - lack of power.

PS: I take for granted that you have checked thermostat and temp??

I will do #1 this afternoon, I will try to locate a carb sync, and follow that lead, I bought a set.of reeds that I.plan on installing just because these are 28 years.old. I have no means of checking temo but I.did test.my overheat alarm and it works.

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

What was your carb cleaning procedure?

The first time I just did a clean soak blow out and re assembled, the 2nd time I did another soak and blow out with a rebuild kit, I did not change the freeze plugs, 3rd time I.did another soak and blow with a full rebuild kit and changed tge freeze plugs. I blamed the carbs for the better half of this whole issue.

 

[glenn property of pam]

Re: 1983 Johnson 75hp, completely out of ideas.

the rpm you mention of 2k plus........are you reading this off a digital timing light thats used on 4 stroke motors? if you are then you need to divide the rpm by 2 for a 2 stroke

 

[Haffiman]

Re: 1983 Johnson 75hp, completely out of ideas.

Check that engine actually reaches operating temp and the function of the thermostat. Borrow an IR gun, temp around 140-150 at the thermostat housing inlet.

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

the rpm you mention of 2k plus........are you reading this off a digital timing light thats used on 4 stroke motors? if you are then you need to divide the rpm by 2 for a 2 stroke

Cleared that up! Thx. Still garbage over here... Trying to find a certified mec to come check the electrical system over.

 

[DWP]

Re: 1983 Johnson 75hp, completely out of ideas.

Check that engine actually reaches operating temp and the function of the thermostat. Borrow an IR gun, temp around 140-150 at the thermostat housing inlet.

That I can do. I'll report back.