1984 Johnson 70 Won't Run At Full Without Priming

[Straightup]

This engine usually has no problems, but I was not able to use it last summer, so it has sat for 2 years (garaged). I got it out this year and it was EXTREMELY difficult to get it running. Once running it would start and run at 1/4 throttle similar to how it normally would. I would advance the throttle to full and it would die right away, but if I pumped the prime button, the one on the key on the console, it would sputter and eventually go to full throttle - and only stay there if I held that prime on the key in. If I let off on the prime, it would die instantly and sometimes even if I was priming it would die, but fortunately we made it back to the dock.
The fuel was half 2 year old fuel and half fresh. My son in law and I looked it over for anything obvious and did not find any pinched fuel lines, leaks, or things like that.
This forum has been super helpful to me in the past and I am grateful for your responses.
Jeff - "Straightup"

 

[flyingscott]

Clean the carbs and put a good rebuild kit in them.

 

[TrueNorthist]

The poster before me has the correct solution. Hard starting and a primer Jones indicates dirty carbs, likely due to booze in the gas. Go sober (methanol free gas) and use stabil. Your motor will love you for it. Use old gas in molotov cocktails only.

 

[oldboat1]

Methanol in reasonable amounts can burn off some water (in reasonable amounts). It's found in Heet or similar products.

2-yr old gas is still 2-yr old gas, whether diluted or not. Siphon it out and use it in the lawn mower. Don't do any serious troubleshooting on the outboard until attempting to run on fresh gas.

 

[TrueNorthist]

Some other time, preferably in private OB1, I'll respectfully disagree with you. I take my liquor neat, same with gas, although in substantially lower quantities.

 

[racerone]

Outboard motors should be stored with carburetors EMPTY so that jets do not plug with fuel residue.----So clean the carburetors.-----An elegantly simple job.

 

[Straightup]

Thank you for everyone's responses. I have a busy next few weeks, then I'll get to it after that.

 

[Straightup]

I'm looking for the correct procedure to rebuild my carbs.
I saw this post by havoc_squad on a thread concerning a 115 Johnson.
Would there be anything different with my 1984 70 Johnson?
"If you want to know the proper steps for rebuilding the carb you have, I highly recommend you buy a factory/OEM service manual and follow it.

It takes three key things for a proper carb rebuild:

1. Take it completely apart per OEM service manual, including the Welsh Plugs and re-assemble correctly per service manual. Buy a geniune OMC/BRP carb rebuild kit with carb/intake manifold gaskets, not aftermarket. You take a significant gamble on many aftermarket marine carb rebuild kits.

2. Set the carb linkage correctly per OEM service manual for the link and sync procedure.

3. Verify the throttle cable linkage is set correct and you have the correct pre-load pressure to return the throttle arm back to its stop to minimum idle."

 

[racerone]

Do one carburetor at a time.------Make sure you find the high speed jet ( orifice plug ) in the carburetor bowl.----It needs to be clean..---Remove drain plug on the bowl to find that item way inside that hole.----If you work carefully you often do not need to worry about the mystery " link & sinc " procedure.

 

[Straightup]

Thank you for that information racerone.

 

[oldboat1]

Did you replace the old fuel? (Mixing with fresh fuel won't solve problems created by old fuel.) If you have water contamination in the system, Heet or similar products containing methanol (not to be confused with ethanol) can help depending on how much water you have. If you have a built in tank, best to use a portable one with fresh fuel until you can clean out the main tank. You want to avoid contaminating freshly cleaned carbs with old fuel.

 

[Straightup]

Update. I took it to a local marina. They had OEM carb kits, but the tech said he didn't do a full rebuild because he was able to free up all the blocked passages. Took it out right after I picked it up and it runs like a dream. Took it out with the kids and we had a great day on the lake! There was a couple of times that I thought the idle seemed a little low, but overall it is running like new!

 

[oldboat1]

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