1976 70 HP Johnson no power under a load

[Johnmari]

I have already done the carburetor update and cleaned them. Replaced the strater, crankcase gasket, fuel pump, primer bulb with hoses, spark plugs and one coil that was bad. I have 120 psi on all cylinders. It will run good on muffs but go put it in the water and it will not stay running or will only run on low idel and only for a short time. I am at a loss and don't know what else to try please help I JUST WANT TO GO FISHING!

 

[bonz_d]

Looking through the trouble shooting chart in the manual I have it still points to the carbs. Or possibly an air leak at one of the gaskets you replaced.

Carb list in order;
Dirt in carb
Ignition timing screw loose
Inlet needles worn or stuck
Incorrect float setting.

Next in line would be, Exhaust gas Entering Carb
Exhaust cover screws leaking
Adapter gaskets leaking
Cracked exhaust housing
Exhaust adapter to cylinder screws loose or missing

So there is a starting point for you, good luck and I hope you find it.

 

[Woodonglass]

Are you sure your floats are working properly. Sounds like it's not getting fuel.

 

[Bosunsmate]

What happens if you keep priming the bulb to act as a manual fuel pump?

 

[Bosunsmate]

What do your sparkplugs look like?

 

[Johnmari]

What happens if you keep priming the bulb to act as a manual fuel pump?

Nothing it stays the same

And the floats look good they look like they are set right

Plugs look good they are new

I am going to take the carbs back off and check to make sure nothing from the old pump is stuck in there

 

[Bosunsmate]

Plug colour- i meant what do the electrodes look like- coffee brown- good, oily not good, white not good, are they similar to each other etc

 

[boobie]

Do a cylinder drop test on it to see if it's running on all the cylinders.

 

[Johnmari]

Number one was coffee brown two and three still look new like no real change. I pulled and checked spark and it was good on all. Then I pulled plug wires while it was running the top one made it die the one in the middle made it run bad and the bottom one had no change. Is that because of a bad coil or a dead cylinder or bad power pack? It was sparking when I checked the spark on it. I have already replaced the top coil it is new and was told the other ones was good but now I am not so sure? Thanks for all the help.

 

[racerone]

Jumping a gap of 7/16" in open air is " good " spark...--Laying plugs on the block is not a good test.------Were the high speed jets that are in the carburetor bowl removed for cleaning ?

 

[Johnmari]

Yes they was cleaned before I changed the fuel pump. I think I might have to pull and clean again maybe sucked in something from old pump. I was worried about the no change on the bottom cylinder when plug wire was removed

 

[Johnmari]

Jumping a gap of 7/16" in open air is " good " spark...--Laying plugs on the block is not a good test.------Were the high speed jets that are in the carburetor bowl removed for cleaning ?

not sure what you mean by open air how would you check it without something to arc to?

 

[racerone]

You need to make something that has a 7/16" gap to do a proper test for spark.-I have used such a device for 40 years +-Laying plugs on the block is not a proper test here.

 

[Johnmari]

You need to make something that has a 7/16" gap to do a proper test for spark.-I have used such a device for 40 years +-Laying plugs on the block is not a proper test here.

Like what do you have a picture of something like that

 

[racerone]

I have the factory tool , 2 of them.-You could use 2 pieces of wire stapled to a piece of plywood.----Staple them with a 7/16" gap in between them.----Stick one end in the spark plug boot and the other wire to ground with an aligator clip.

 

[Johnmari]

Thanks Racerone I will make one and see what happens. ? If it doesn't jump is that the coil or power pack?

 

[bonz_d]

Like what do you have a picture of something like that

Go to any auto parts store, mine was about $15.00

 

[Bosunsmate]

Number one was coffee brown two and three still look new like no real change. I pulled and checked spark and it was good on all. Then I pulled plug wires while it was running the top one made it die the one in the middle made it run bad and the bottom one had no change. Is that because of a bad coil or a dead cylinder or bad power pack? It was sparking when I checked the spark on it. I have already replaced the top coil it is new and was told the other ones was good but now I am not so sure? Thanks for all the help.

Sounds like your middle and bottom cylinders arent getting fuel.
Sort that out before you try running it again as you could blow it running it dry.
Ground out all your plug wires then turn it over with the starter for a few seconds, stop for thirty then repeat, remove the plugs check they are all wet with fuel

 

[Johnmari]

Sounds like your middle and bottom cylinders arent getting fuel.
Sort that out before you try running it again as you could blow it running it dry.
Ground out all your plug wires then turn it over with the starter for a few seconds, stop for thirty then repeat, remove the plugs check they are all wet with fuel

Is that a high pressure jet carb problem?

 

[racerone]

The high speed jets are found / screwed into the bottom of the float bowl.----We can not count how many times these have been overlooked by a novice outboard mechanic.