# 1974 Johnson 9.9 hp won't start



## Scott06z71 (Nov 5, 2013)

I have a 1974 Johnson 9.9 hp. I cranked it yesterday it ran for a few minutes then it quite. I could not get it started again. I pulled the gas line off the carb that comes from full pump. I pumped the primer bulb and it squirted gas out of this gas line. I pulled the pull rope and a little gas came out of the gas line. I checked the screen in the fuel pump, it was ok. I connected the gas lines back and wiped up the spilled gas. I pulled spark plugs out one at time connected plug wire to it and held plug end (with insulated pliers) to the block and had wife pull the pull rope. It was dark by this time so I could see the blue spark, had spark on both plugs. The gas hoses look ok. My primer bulb gets hard when I pump it and it stays hard the whole time. I have had this boat a couple of months and it has never really run perfectly. It has acted like it was not getting enough fuel, the motor would bog when giving it full throttle. I had replaced gas hose/primer bulb from tank to motor. Yesterday I put on a new plastic gas tank, the old tank had a split in it and I thought that might be my problem. I had my wife keeps pumping primer bulb while I tried to start motor and no luck. I tried again today and no luck. I cleaned the spark plugs with gas before I cranked it the first time. I checked them when I pulled them out to check spark. Can anybody gives me any ideas what to check or try?


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## stevesecotec02 (Nov 6, 2013)

Could be a problem with the carb. Do you usually either drain gas from carb or run it till it runs dry at end of day? Doesn't take long for ethanol to gum up a carb. If you don't know how long its been since carb was taken off and cleaned or rebuilt I would start there.


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## SumDumGuy (Nov 6, 2013)

shoot some premix through the carb. If the motor starts, then you indeed have a delivery problem.

you could bypass the pump with a raised tank going to the carb inlet (gravity feed). This would tell you if the pump is actually functioning. Although it sounds like it is if repeated pumping of the bulb did not work.

and like Steve mentioned it could be a carb issue.

Here's a kit:
https://www.ebay.com/itm/Carburetor..._Accessories_Gear&hash=item3f24615a1f&vxp=mtr

Might check this one, too:
https://www.ebay.com/itm/398452-043..._Accessories_Gear&hash=item439c9fbfc9&vxp=mtr


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## Scott06z71 (Nov 6, 2013)

Today I fooled around with it a little. I pulled the starter rope about 5 or 6 times, still would not start. I pumped the primer bulb first. I then pulled both plugs out and they were dry. I would think they would normally be wet with gas. I'm thinking about buying a carb kit and full pump kit and rebuild them both and replace the gas hoses on the motor. I was reading on a link that I found on this site an article that lee Roy winser wrote that has a lot of info for these old Johnson motors. Due to my work schedule it may be next week before I can work on it again. I will post an update after I get the both of them rebuilt. If anybody has any other suggestions please post them.


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## sr71 (Nov 6, 2013)

How is the compression?


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## cajuncook1 (Nov 6, 2013)

- should really check your ignition using a spark checker but for now if you saw blue spark on both then you can call good for now.

- Your motor uses a points and condenser ignition and it uses a low tension system. Driver coil, points, and condenser under the flywheel. There are two external ignition coils mounded externally that connect to the spark plugs.


Here is 2 youtube videos that will help you remove the carburetor and perform carburetor maintenance and cleaning and reinstall.

video 1

https://www.youtube.com/watch?v=IKVckfUYTEM

video 2

https://www.youtube.com/watch?v=DeN2cd-4MgU


Make sure you have fresh 87 octane gas mixed with TC-W3 2 cycle oil mixed at 50:1 fuel oil ratio. If you are uncertain the age of the fuel in the tank, replace with fresh fuel mix.

-- Make sure your throttle is set to start and make sure your vent screw on your tank is open. Don't forget to pull the chock when you first start it and push it in when it starts.


*Part diagram of the carburetor*

https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1974&hp=9.9&model=10424G&manufacturer=Evinrude&section=Carburetor
*
carburetor kit with new float*

https://www.marineengine.com/newparts/part_details.php?pnum=OMC0439072
*

Here is diagram of your ignition system.*


https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1974&hp=9.9&model=10424G&manufacturer=Evinrude&section=Magneto


Make sure your kill switch wires are not damaged and causing a short.


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## Scott06z71 (Nov 7, 2013)

Thanks for the info Cajuncook1. I don't know the age or mix ratio of gas it was in the old tank from previous owner. That tank had a crack in it. I poured that gas to the new tank. The new tank is a plastic self venting Attwood tank from Academy Sports. The previous owner told me that he had replaced spark plugs and rebuilt carb. I'm going to do it myself so that I know for sure it was done. I will check out the links you posted.i will have to google a spark tester and see if I can buy one. I was not sure about checking the points and condenser.


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## Scott06z71 (Nov 8, 2013)

I ordered a service manual from eBay today. I should have it by next weekend when I start back working on my motor.


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## SumDumGuy (Nov 8, 2013)

Here is a worthwhile link if you have not seen it...

https://www.leeroysramblings.com/Johnson 9.9_15.htm


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## pafree (Nov 8, 2013)

my new to me 20 hp johnson had the same issues. i put a carb kit in it because it was missing the rubber gasket/weird shape o-ring around the idle adjust screw but still didn't help. the engine would run for a couple of minutes and then stop. i would pull the fuel line off the carb from the pump and get the same results you were getting. i rebuilt the pump and it solved the issues.

does it have a real choke or a primer choke?


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## Scott06z71 (Nov 9, 2013)

Hey thanks for the great feedback guys. Sumdumguy thanks for the link. I have been reading info from the link. That is a lot of good info. And pafee I was thinking of rebuilding the fuel pump first because it is the easiest then carb next. I'm going to try one thing at a time so if something else goes wrong I will know what I just changed and go back to that. I will post the fix once I get it going.


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## frankc (Nov 10, 2013)

You may have a leaky crankcase seal. 

If anyone closed the low speed needle too tight, it could have been damaged against the seat.

If you have been running with alcohol in the gas, it may have damaged some elastomer parts also. That is common today.

I believe that year model came with a carb which was replaced due to running problems also.


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## Scott06z71 (Nov 12, 2013)

I did a compression check today and had 125 on both cylinders after 3 pulls. Next step I will rebuild fuel pump and carb and replace gas lines. It will be the weekend before I can get to that.


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## Scott06z71 (Nov 12, 2013)

I found some more info in my research today. This may be contributing to my problem. I got a new 6 gallon Attwood gas tank. My old tank has a leak in it is why I got a new tank. It sayes that for protection from the effects of pressure within your fuel system, add Attwood Fuel Demand Valve (9300FDV7) to keep pressurized fuel from flooding your enging and to prevent fuel leaks. I have a new fuel line & primer bulb too and now looks like I will have to cut it to splice this in between tank and prime bulb. (nice) I'm going to order one and put it on too I guess. 
Has anybody else used one of these with the newer style gas tanks?

Here is a link to read about it: https://www.attwoodmarine.com/store/product/portable-fuel/fuel-demand-valve

I have found it online at several places ranging from $18 at Amazon up to $30.


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## SumDumGuy (Nov 13, 2013)

I have an attwood tank and do not run one of those high speed valves they sell.

I think you would be better served using the coins to rebuild/replace the fuel pump and rebuilding the carb. Both are extremely easy and straight forward.

$.02


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## cajuncook1 (Nov 13, 2013)

.


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## cajuncook1 (Nov 13, 2013)

.


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## Scott06z71 (Dec 26, 2013)

Well it has been awhile but I finally was able to work on my motor today. I rebuilt the fuel pump & carb with OMC kits. I dumped the old gas from tank and put fresh gas with 50:1 mix of oil. I put new gas lines and hoes clamps. I also got one of the Attwood fuel demand valves to add to the gas line on tank, it sayes to install it between tank and primer bulb. It was too late to try it when I finished this evening. I will crank it in the yard tomorrow with test tank, if it runs well then I will be taking it out for a test run at the lake. Hopefully now it will plane the boat off. The carb was not gummed up but in the float bowl it was orange, I will attach pictures. Looked like rust. It is gone now.


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