Trouble with 1975 Johnson 70Hp outboard.

[Saskatoon2005]

Hello All,

As stated, I have a 1975 Johnson, 70Hp outboard. I took it out for the first time today, and it started right up and ran fine. We fished around the lake and then shut the motor down. No problems...until I tried to start it again....it would just tun over, but no start, no sputter, no nothing.

I did figure if i played with the throttle linkage connecting the three carburetors together...I would get it to start. So i know it is a fuel problem. You see at first I thought it was because i forgot to release the pressure from the gas tank, and I starved the engine...but i couldn't get it to start, and the bulb wasn't flat, so couldn't be that. I was able to get it started right up and then when I turned it off again, I couldn't get it started until I played with the throttle linkage, again.

I would like to know what steps I should take to get this started, after I shut it off, and not have to worry about it not running, having to play with the throttle. You see I have the powershift throttle handle, and I can't accelerate the engine without it going into gear.

What do I do to rectify this? Please help

 

[Joe Reeves]

Re: Trouble with 1975 Johnson 70Hp outboard.

I'm not familiar with the "powershift throttle handle" BUT the engine must have some way of having the throttle advanced slightly in order for it to start. On some controls, the throttle handle pulls out sideways to allow this feature.

There are a few engines that will start at a dead idle, but they are few and far between.

 

[Saskatoon2005]

Re: Trouble with 1975 Johnson 70Hp outboard.

Well it has a warmup lever, that increases rpm, and a toggle switch choke, but even after it is warm it cuts out and when I advance the throttle linkage, it blows a huge cloud of smoke, and then settles down, and goes back to idle...strange that it will idle, but it won't start, I know it is a fuel issue.

 

[Joe Reeves]

Re: Trouble with 1975 Johnson 70Hp outboard.

Remove the carburetor face plate. Pump the fuel primer bulb up hard to see if any of the carburetors might be flooding..... fuel would flow out of the faulty one.

Also, check to see that the electric choke is operating as it should, that is all choke butterflies closing completely when engaged.

Whether the fuel pump has a third line that goes to the crankcase to operate the pump, or via a small hole in the back of it thru as thick gasket to the crankcase..... check to see that no fuel flows out of that area when the fuel primer bulb is pumped up hard. If it does, the pump diaphram is cracked.

 

[Saskatoon2005]

Re: Trouble with 1975 Johnson 70Hp outboard.

Thanks Mr. Reeves,

I am pretty sure it was your help that got my 1961 Johnson 40hp running. So I'll do whatever you say....I'll check that today, and let you know what I find.

Patrick

 

[Saskatoon2005]

Re: Trouble with 1975 Johnson 70Hp outboard.

It looks as though the carbeuretors are all leaking? I mean I can see a drop of fuel at the bottom of each carburetor....what does this mean, and what should I do?

 

[dennyirl]

Re: Trouble with 1975 Johnson 70Hp outboard.

Read this post.have same issue with same engine.just wondering if anyone found a solution??cheers

 

[Joe Reeves]

Re: Trouble with 1975 Johnson 70Hp outboard.

A single drop of fuel really says nothing. Does fuel actually leak from any carburetor when the fuel primer bulb is pumped hard?

And did you check out the fuel pump as I mentioned?

Let me know if you do what I suggest and the results.

 

[Saskatoon2005]

Re: Trouble with 1975 Johnson 70Hp outboard.

Mr. Reeves,

I did as you asked and here is what I have found....

1) First, the last owner has used zip ties to attach all the fuel lines to their respective places.

2) Second, I did remove the plate covering the carb faces.

3) I did pump the fuel bulb and did not notice any carb flood, until the bulb was hard.

4) Here is what I did notice...the fuel DID squirt out of the connection from the fuel line to the fuel pump where the previous owner had used a zip tie.

5) upon inspection, I also noticed that there was fuel at the other connection leading away from the fuel pump to the carbs...

Mr. Reeves...I would like to know what this effect might have on the outboard? What would a leaking fuel pump cause for the outboard to not restart unless I open the throttle completely full, and have the large smoke emit from the outboard upon startup when it won't just start on its own...thanks for any input you may add to this...I will pick up stainless steel screw type connectors and replace the leaking ones...

...as a side note....is this common use to use zip ties to seal connectors? Seems pretty weak to me....but just curious to know if that is common practice. I will add a pic of what it looks like with the zip connectors being used, and where the fuel leak is...as well, there is still a drop of fuel at the bottom of each carb, where the screw is to release any fuel left in the carb. Just thought you might have some insight into that.

Thanks again Joe....

Patrick

 

[Saskatoon2005]

Re: Trouble with 1975 Johnson 70Hp outboard.

Here is the pics I promised of the outboard. You can see the zip ties at the connection points of the outboard. Normal?

 

[Joe Reeves]

Re: Trouble with 1975 Johnson 70Hp outboard.

The use of zip ties is a common practice. This has been a practice even of OMC for many years past, and I've used them constantly ever since they came into existence.

If a hose leaks and the tie strap is tight, the hose needs replacing. One can use the small stainless steel screw type clamps but that can exert excessive pressure on the plastic fittings...... and it really doesn't look very good.

Did you check the fuel pump for a cracked diaphram as I mentioned above?

From what you've said, it appears that the engine is flooding somehow after you shut the engine down. I can only think of the fuel pump diaphram and/or the carburetors if this is the case.

After running, then shutting the engine down to fish or whatever, the heat from the engine naturally rises, adding heat to the already hot stator under the flywheel. The stator is the beginning point of the ignition and charging system. A failing stator when cold may function fine (for awhile), but when hot the output voltage to the powerpack drops which results in weak, erratic, or no ignition...... untill it cools down somewhat.

Should this be the case, cranking the engine attempting to start it would result in excessive fuel being drawn into the crankcase. Eventually the stator cools down, supplies the powerpack with the needed voltage, the ignition energizes and the engine starts with a resulting blast of smoke as the excessive fuel is blown away (Something to consider).

Many stators when failing will crack and start to drip a sticky substance down on the powerhead.... look for that. Other than that, check the ohm readings of the stator wires as per your manual.

 

[Saskatoon2005]

Re: Trouble with 1975 Johnson 70Hp outboard.

How do you check the fuel pump for a failed diaphram? I did not see any potting material melted onto the powerhead from the stator.

 

[Saskatoon2005]

Re: Trouble with 1975 Johnson 70Hp outboard.

how do you check the fuel pump?

 

[Joe Reeves]

Re: Trouble with 1975 Johnson 70Hp outboard.

Whether the fuel pump has a third line that goes to the crankcase to operate the pump, or via a small hole in the back of it thru as thick gasket to the crankcase..... check to see that no fuel flows out of that area when the fuel primer bulb is pumped up hard. If it does, the pump diaphragm is cracked.

If a 3 line fuel pump, remove the hose that goes from the fuel pump to the crankcase. Pump the fuel primer bulb. If any fuel flows out of that pump fitting, the pump diaphragm is cracked.

If a 2 line fuel pump with a thick gasket in back of it, remove the two screws that attach the pump to the powerhead. re-insert those 2 screws in the pump and put 2 nuts on the back of them so that you can tighten the pump together and eliminate any leakage thru the sides. Pump the fuel primer bulb. If fuel flows out the small hole in the back of the fuel pump, the diaphragm is cracked.

 

[Saskatoon2005]

Re: Trouble with 1975 Johnson 70Hp outboard.

The fuel pump is fine...I took it apart and looked at the diaphram, no punctures, it is still intact. So I can rule out the fuel pump.....now what?

I can see a film of duel and oil over the whole front of the motor....do I start taking the carbs off one by one and checking them, or what?

I can't see any leaks directly, just the film...and the negative results of the motor that quit runs, when the prime bulb gets dry....so where else can the fuel leak out of?

Are the carbs flooding or something?

Please help me out!

 

[The-Machinist]

Re: Trouble with 1975 Johnson 70Hp outboard.

Do you have a friend that can loan you his small portable fuel tank and hose assembly? If it runs on another tank and hose it could point you in the right direction finding the problem.

 

[Saskatoon2005]

Re: Trouble with 1975 Johnson 70Hp outboard.

How would using another tank point me in another direction? I do not understand? I don't think that is the problem, as there is unburnt fuel all over the front of the motor! It seems like it is coming out somewhere from all the vibration during driving. I mean, until it becomes starved, it runs beautifully. I just need to repair the leak somewhere, and I am sure it will run beautifully again.

What else could cause this problem?

Patrick

P.S. thanks for the replies...

 

[The-Machinist]

Re: Trouble with 1975 Johnson 70Hp outboard.

It was the "dry bulb" comment that made me wonder if you had an air leak in a fuel line. Is it possible that the reeds are warped or rusted, letting fuel vapor escape from the carb inlets?

 

[Joe Reeves]

Re: Trouble with 1975 Johnson 70Hp outboard.

Unburnt fuel on the front portion of the engine...... When the engine is tilted, the fuel that is in the carburetors would have a tendency to flow out. If the face cover gaskets are flawed or missing, the front portion of the engine is where the fuel would be found.

If the fuel primer bulb functions properly, that is it draws fuel normally as it should and springs back to its normal inflated position quickly, and after pumping it up hard (priming the entire fuel system), there is no change in the starting problem, I would assume that the tank and hose are okay.

Pointing you in the right direction..... Say you have a friend that will loan you a tank and hose that functions properly on his engine. Your engine does not run any better with his tank and hose. That tells you that the problem DOES NOT pertain to the tank and hose. This points you in the right direction where the problem lies..... the engine. However, the previous above paragraph pretty much covers that area also.

When the engine is hot after running, shut down for a bit of fishing or whatever, then when attempting to start.... it will not start. This could be a ignition problem as I stated above in my 4th reply of May 7th. The fuel that you see around the engine could very well be throwing you a curve, leading you away from a ignition problem.

Have a spark tester handy, one where you can set a 7/16" gap. When this problem occurs, remove all of the spark plugs and do a spark test. The spark should jump that 7/16" gap with a strong blue lightning like flame, a real SNAP! The 7/16" gap is important. A test using the spark plugs is a waste of time.

 

[Saskatoon2005]

Re: Trouble with 1975 Johnson 70Hp outboard.

I am going to do a compression test this morning and a spark test as well, I'll let you know what I find....

Thanks for your help.

Patrick