1975 70 HP Johnson Fuel issue?

[Paddy60]

Hello,

First time poster. Long time looker.

I just recently bought a 1975 70 hP, 70ESL 75E

At the time of purchase, we could get it to start but only for a few seconds and with a bit of hand throtle 30 sec. Checked compression and all 3 were 125 psi. So me thinks, rebuild the carbs and fuel pump. I did just that and replaced all fuel lines and the tank hose. When I was in the carbs, they looked clean, but in any case I cleaned away. same for fuel pump, nothing a miss. So when she was all back together, I was hoping she just fire up and run oh so fine. NO luck. pretty much the same!

Any checks I should do at this point? I thought I could check to see if the pump is working by disconnecting the line to the carbs and see if aI get fuel while cranking. I can see if the remaining few items in the fuel system are clear, Drop tube into tank, fuel hard fittings at tank and motor. I should add, choaking does hot appear to change any thing.

any ideas?

Thank you

Patrick T

 

[busted-bayliner]

Re: 1975 70 HP Johnson Fuel issue?

Hello,

First time poster. Long time looker.

I just recently bought a 1975 70 hP, 70ESL 75E

At the time of purchase, we could get it to start but only for a few seconds and with a bit of hand throtle 30 sec. Checked compression and all 3 were 125 psi. So me thinks, rebuild the carbs and fuel pump. I did just that and replaced all fuel lines and the tank hose. When I was in the carbs, they looked clean, but in any case I cleaned away. same for fuel pump, nothing a miss. So when she was all back together, I was hoping she just fire up and run oh so fine. NO luck. pretty much the same!

Any checks I should do at this point? I thought I could check to see if the pump is working by disconnecting the line to the carbs and see if aI get fuel while cranking. I can see if the remaining few items in the fuel system are clear, Drop tube into tank, fuel hard fittings at tank and motor. I should add, choaking does hot appear to change any thing.

any ideas?

Thank you

Patrick T

try checking the pump as you said make sure you havent got the hoses on the pump mixed up

 

[Paddy60]

Re: 1975 70 HP Johnson Fuel issue?

Busted,

I did just that. Disconnected to out flow and hooked an old hose. Tryed the squease bulb but that shot gas 2 feet up. Gently primmed the bulb and then cranked. It had a good flow of gas. It even started for a few seconds

What I did notice is that if I attempt to start it, it will run for a few seconds. If I imediatlely try again, nothing, even with choke. But if I wait a few min, she will start again....for a few seconds. Basically no choke needed, just time between trys.

To me this sounds like a dry bowl? sucks the fuel out and in time fills?

Patrick T

 

[busted-bayliner]

Re: 1975 70 HP Johnson Fuel issue?

Busted,

I did just that. Disconnected to out flow and hooked an old hose. Tryed the squease bulb but that shot gas 2 feet up. Gently primmed the bulb and then cranked. It had a good flow of gas. It even started for a few seconds

What I did notice is that if I attempt to start it, it will run for a few seconds. If I imediatlely try again, nothing, even with choke. But if I wait a few min, she will start again....for a few seconds. Basically no choke needed, just time between trys.

To me this sounds like a dry bowl? sucks the fuel out and in time fills?

Patrick T

have u checked the float level with the carb bottom off sound like it starving for fuel i would double check the floats an needle

 

[busted-bayliner]

Re: 1975 70 HP Johnson Fuel issue?

when u get the not start issue have you checked for spark ?

 

[Paddy60]

Re: 1975 70 HP Johnson Fuel issue?

Busted,

I have not. I did pull the carb bowl drain and fuel came out. I guess I could shoot a small qty of fuel mix at the point it's dieing to see if that revives it

thanks for the feed back.

 

[mrcj001]

Re: 1975 70 HP Johnson Fuel issue?

Check the quality of the spark. Get a $10 spark tester and see if you are getting a blue spark that will jump 7/16- 1/2 "....if not the power pack could be the culprit if as not been replaced. They get weak in time and fail.

 

[boobie]

Re: 1975 70 HP Johnson Fuel issue?

Three things to make a mtr run, compression, ignition and fuel.

 

[Paddy60]

Re: 1975 70 HP Johnson Fuel issue?

Boobie,

Compression is good, rebuilt the carbs and entire fuel system. Tricky part is there is spark to get it started for a few seconds. I need to check the quality of the spark. Using the CDI diagnostic, I pull the rectifier off and noticed the red wire was rotted and touching the metal housing. All the other wiring is in good condition. As instructed by CDI, I pulled the two yellow wires. The result was I was able to get it to run a few seconds again but did this three times in a row. Where as before, after it ran in the short burst, it would have to sit a few mins before I could get it to repeat.
Logic tells me if I really want a dependable motor, I should just replace; the power pack, all tree coils and the Rectifier. My only fear is that it could be the stator and or the timer base. how common is it that it could be the stator or timer base?




Thanks for all the help

 

[eavega]

Re: 1975 70 HP Johnson Fuel issue?

Not to step in, but CDI has a full diagnostic for the ignition system, that will tell you if your stator, timer base, etc. have gone bad. I would suggest that you get yourself a multimeter with DVA adapter, or a multimeter that reads peak voltage and run those tests. If you already have a good multimeter, the adapter is less than $30. That is a heck of a lot cheaper than replacing the stator and timer base, which IIRC for your motor is over $100 for each.

Rgds

 

[Paddy60]

Re: 1975 70 HP Johnson Fuel issue?

Eric,

I'm in the process of making a DVA adapter. I will not replace the stator or timer base unless confirmed bad. Really two reason, they are under the flywheel and they are pricey. What does IIRC stand for?

Patrick t

 

[StickyWidget]

Re: 1975 70 HP Johnson Fuel issue?

Eric,

I'm in the process of making a DVA adapter. I will not replace the stator or timer base unless confirmed bad. Really two reason, they are under the flywheel and they are pricey. What does IIRC stand for?

Patrick t

IIRC = If I remember correctly

 

[Paddy60]

Re: 1975 70 HP Johnson Fuel issue?

I did the DVA reading on the stator, connected and disconected to Power Pack. It was suposed to be in the 150-450 range connected and un connected. It was 129 connected and 450+ disconnected. That tells me the Power Pack was bad. I replaced the Rectifier, all 3 coils and the Power pack. I will reconfirm all wires and give it a try. hopefully with the new ignition and refurbed fuel system, all will be fine.

I'll keep you undated, Thank you for you help

 

[Paddy60]

Re: 1975 70 HP Johnson Fuel issue?

She started and ran very smoothly. Thanks for all your help.