Johnson 1984 70 HP

[Tony L S]

Hello,

I have a 1984 Johnson 70hp outboard. This winter I ordered carb kits and rebuilt the three carburetors. The motor ran pretty well before the rebuild but would not start at times, it would flood and sometimes have trouble when trying to lug onto the trailer.

After rebuilding the three carbs I also rebuilt the primer solenoid and replaced the fuel pump(OEM). I replaced all the fuel lines from the tank to the motor and all the fuel lines between the tank line and the carbs.

I tried to fire the motor up the other day but it would barely run. When I would lift the start on the control box the motor will run for 15 seconds or so but then dies. I am not really sure what to do next. Any help is appreciated.

1. I plan to look for air leaks around the carbs.
2. Check compression(even though it ran fine before the rebuild)
3. Remove the carbs and check the floats(the only adjustment on these cabs)

Any other ideas? Thanks!

 

[oldboat1]

Get an adjustable spark tester (open air -- not the inline type), fully charge the battery and measure spark -- should see around 1/2" and bright. This would tell you the ignition is in good shape.

If ignition and compression is not an issue, revisit carb cleaning procedure. Remove the core plug on top, and soak top and
bottom of each carb (linkage attached). Use a solvent strong enough to clean fuel varnish. Finish by running soft wire through every opening/each orifice. I don't remove the jets (potential damage), but open them up and soak with the carb body. If the float valve needle accepts the wire clip, the clip needs to be used.

Do a search here for the link and sync procedure.

 

[Tony L S]

Thanks for the reply. I have purchased an adjustable spark tester. Should I test each cylinder or just one? I have also purchased a compression gauge. I assume you do not need a special gauge for a 2 stroke?

I will do these test and post the results.

As far as synchronization of the carburetors I have completed this process. All butterflies are shut when the motor should be idling. When I rebuilt the carbs I placed them in chem-dip and cleaned them with an ultrasonic cleaner. I did not remove the core plugs as I had no experience with this. The kit did come with replacements.

If the compression and spark are good I will do as you say and remove the carbs.

Thanks again

 

[racerone]

I do not believe you will find any significant air leaks around the carburetors.----Was there any dirt / varnish in the carburetors when you took them apart , yes or no ?----Yes , you check for maximum ignition output on each lead !-----What do you mean by ---" it ran pretty well but would not start at times " ----How long have you owned this motor ?

 

[Tony L S]

Hello,

The carburetors were pretty clean. I would have to say no. I had used seafoam to clean the system at least once a year for the last three years. I have had the boat for three years.

The motor ran well. The engine would die sometimes when loading onto a trailer(lugging the engine at a low RPM) and sometimes it would not start. I noticed this more when I first got to the lake. Seems like it would flood.

Can you post videos on here?

Thanks for your input!

 

[racerone]

Post your compression test results.----And " hard to start " can be caused by a bad battery , bad battery cables , bad starter motor and wrong procedure for starting.

 

[Tony L S]

I will post those results soon. I had to order a compression tool.

I replaced the fuel pump with part number 438557, as this was the part on the boat. When I look up the fuel pump for this model boat it calls for 0394717. Would this make a difference?

Thank you.

 

[racerone]

Makes no difference.------And the fuel pump would have nothing to do with a " hard to start " condition.

 

[oldboat1]

0394717 was the original oem carb -- went through 4 generations of changes to 438557 for 3-cylinder models. For J70ELCRD, however, the replacement carb is 438559.

Can't say whether there would be much difference in operation, and defer to Racerone on that. Agree that the hard starting is a separate issue. If you've been adding Seafoam to your fuel tank, you may be loosening debris from the tank and running it into the carbs (MO).

 

[racerone]

?? the 438559 FUEL PUMP is for V-4 and V-6 models.

 

[oldboat1]

[h=4]0398399 : 0398399 is no longer available but for replacement use part number 438557 for 2 and 3 cylinder motors, for V4 and V6 motors use part number 438559 used in: 1984 Johnson 70 HP (Model J70ELCRD) Fuel Pump Parts[/h] Maybe misread or misprint (sister site).

 

[racerone]

It clearly states that 438559 is for the V-4 and V-6 motors !

 

[oldboat1]

Yes, wouldn't be much question if the OP had a V4 or V6. And the OP may not have J70ELCRD anyway.

 

[racerone]

His 70 HP is a 3 cylinder inline motor !

 

[oldboat1]

I think that's called begging the question.

 

[boobie]

I never heard of that one "begging the question". Whats it mean ??

 

[Tony L S]

How can I tell what model motor I have? I can't seem to find a tag anywhere.

 

[oldboat1]

Look for a tag on the mounting bracket. By '84 I think they were using the type that fades away, unfortunately -- or is rubbed away. Have you posted a pic somewhere? Folks can often ID it that way. Best is one with the hood on, one with it off.

 

[Tony L S]

J7OELCRD I found the tag.

 

[oldboat1]

I never heard of that one "begging the question". Whats it mean ??

assuming as true what you are attempting to show or prove:

R. says this pump is used only on V-4/6s

I said it is apparently used on at least one 3 cyl model.

R. says that can’t be because the pump is used only on V-4/6s