7.5 HP Johnson outboard 1982

J

jes100fish

Seaman Apprentice
Joined
May 7, 2009
Messages
37
I can't keep the engine running. I cleaned the float bowl; this is making it easier to start. Disconnected the fuel line from the fuel pump and cranked the engine - gas is coming out but not a steady stream. Which part do I buy to replace the fuel pump.

If I pour gas into the carbuerator it runs for a few seconds and same happens if I put it into the spark plugs. Can't keep the engine running. I replaced the entire fuel hose, bulb and fittings with a new one - entire section from fuel tank to fuel filter. Bought new gas tank and I'm using new fuel.

Any help would be appreciated.
 
G

"G"

Petty Officer 2nd Class
Joined
May 2, 2009
Messages
150
Re: 7.5 HP Johnson outboard 1982

Jes,
Check the compression. Once that's done and it's good the rest is easy to diagnose. If you squeeze the bulb will it stay running? What's the history on this old engine? Any over heats, ignition issues... Why did you rebuild the carbs? Is there cause for supposing dirty fuel, water in the fuel etc?

In answer to your question, Fuel pump kits usually contain a rubber diaphragm and some gaskets.
 
R

River Boy

Petty Officer 3rd Class
Joined
Apr 18, 2009
Messages
92
Re: 7.5 HP Johnson outboard 1982

Well, it'll run for a while so you got spark.
New bulb/hose/and fittings, you should be able to keep squeezing the bulb and bypass (overide) the fuel pump. Does the bulb pump up? Once the float bowl is full by pumping it should run for a while. 30 sec or a minute or so, fuel pump or no.
I bet you need to go back in there and take a look at the float/needle and seat status. Did you clean and blow out all those carb orifices really good? Little tiny ones in the venturi area that you can rod out with a small copper wire.
Be sure and spray/pour pre-mix in the carb/cylinder area and not unmixed gas.
 
F

film495

Petty Officer 2nd Class
Joined
Apr 8, 2009
Messages
149
Re: 7.5 HP Johnson outboard 1982

how did you set the high and low speed adjustments on the carb, make sure the high speed one is default set to 3/4 or 1 turn out from all the way seated.
 
J

jes100fish

Seaman Apprentice
Joined
May 7, 2009
Messages
37
Re: 7.5 HP Johnson outboard 1982

I will check compression later today. Squeezing the bulb helps it run maybe 2-3 seconds longer. I'll blow out the orifice again. It only has a low idle adjustment - I turned it 1.5 turns out. I'll also check the float and needle. I'm using fuel I bought 2 days ago. If I put gas in the carb it runs for 3-5seconds and same if I put gas in spark plugs. Squeezing the bulb helps it runs about 4-6 seconds. I seems like I'm not getting fuel to the engine.

The motor has not been used for 7 years.
 
Sandhammaren05

Sandhammaren05

Banned
Joined
Jul 30, 2008
Messages
172
Re: 7.5 HP Johnson outboard 1982

The high speed jet is fixed, not adjustable, and if the float bowl was 'dirty' (varnish?) than the high speed jet and other passages are probably clogged as well. Sounds like carb may need to be rebuilt, for one thing. Always run all fuel out of the carb before storing the motor for the season.


jes100fish said:
I will check compression later today. Squeezing the bulb helps it run maybe 2-3 seconds longer. I'll blow out the orifice again. It only has a low idle adjustment - I turned it 1.5 turns out. I'll also check the float and needle. I'm using fuel I bought 2 days ago. If I put gas in the carb it runs for 3-5seconds and same if I put gas in spark plugs. Squeezing the bulb helps it runs about 4-6 seconds. I seems like I'm not getting fuel to the engine.

The motor has not been used for 7 years.
Click to expand...
 
J

jes100fish

Seaman Apprentice
Joined
May 7, 2009
Messages
37
Re: 7.5 HP Johnson outboard 1982

I got it running!!!! I rebuilt the fuel pump and cleaned the carburator again. I also ran a very thin copper wire up the orifice; there was a little resistance the first time, so I'm guessing it had some minor built up. I checked the float and inlet valve; they were adjusted correctly.

I never checked the compression - left message on neighbor's phone to see if he has a gauge, will check it if he does. The manual says to be more concerned with the difference in pressure between the two cylinders. Can somebody let me know what the pressure should be.

Thanks everyone for your helpful suggestions - it really helped me get it running.
 
R

River Boy

Petty Officer 3rd Class
Joined
Apr 18, 2009
Messages
92
Re: 7.5 HP Johnson outboard 1982

I've got an 80 Johnson 7.5. It runs 95 pounds per cylinder on my gauge.
You said it hadn't run in 7 years. While you're in mechanic mode pull the lower unit and put a new impeller in. It's surely needing one.
 
Last edited:
Sandhammaren05

Sandhammaren05

Banned
Joined
Jul 30, 2008
Messages
172
Re: 7.5 HP Johnson outboard 1982

Buy a waterpump repair kit, replace the whole shootin' match if you replace the waterpump. I'd also replace the driveshaft and propshaft seals and o-rings.


River Boy said:
I've got an 80 Johnson 7.5. It runs 95 pounds per cylinder on my gauge.
You said it hadn't run in 7 years. While you're in mechanic mode pull the lower unit and put a new impeller in. It's surely needing one.
Click to expand...
 
You must log in or register to reply here.
Top