1978 johnson 9.9 stalling on top end

stratos201s

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I just bought a 1978 johnson 9.9 outboard and it starts and runs great. I have had great luck before on this forum and you guys are awesome!! I appreciate every bit of your knowledge of these outboards! Engine is Pull start. I ran it out on a 12 ft jon boat and runs 5.1 mph gps and I am about half throttle. As i open the throttle from there it bogs real bad and will die unless I lower the throttle back to half or less. It seems to run wide open in neutral if I open throttle but not with in forward gear. I am confused as to whether it is carb, fuel line, ignition maybe....seems to run good down low. Any help would be greatly appreciated!! I just wanna fish!
 

Daviet

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Re: 1978 johnson 9.9 stalling on top end

Start with a compression and spark. If they check out OK, it ssounds like you have a fuel problem. Try squeezing the primer bulb while at high speed under load, if that helps you have a fuel pump problem, you have checked the filter screen in the fuel pump? If that does not help, it's time to overhaul the carb.
 

dradford78

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Re: 1978 johnson 9.9 stalling on top end

Check that both of your core plugs are there. I had the same problem on my 64 johnson and it turned out that one of the core plugs was missing and if I held my finger over the hole it would run great at full throttle.
 

stratos201s

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Re: 1978 johnson 9.9 stalling on top end

Thanks! Your help is always timely. I will check all these today. I'm pretty mechanically inclined just no experience on these outboards. I am not sure I know what a core plug is. Thanks again!
 

AlTn

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Re: 1978 johnson 9.9 stalling on top end

if you'll google..Leeroy's Ramblings...outboard repair articles....this is the most extensive amount of information on the 9.9-15 hp. at a single site that I am aware of...a real benefit for the diy person...many folks here have worked on and owned these models as well...marineengine.com..boats.net...shop.evinrude.com....all have diagrams of your motor's various components
 

stratos201s

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Re: 1978 johnson 9.9 stalling on top end

ok so update....turns out the engine has a rev limiter while in neutral that only allows half throttle unless in gear to prevent harming the engine. That said, I rebuilt the carb using the sierra kit and changed the plugs with new NGK's and still the same story. I also replaced the fuel lines with new ones. I can put half throttle and the boat runs about 6 mph and as soon as I go full throttle it starts to stall. I checked the core plugs and they have actually been leaded in so no leakage there I'm assuming. The engine starts first pull most of the time and runs great up to half throttle. Mixture screw is 1.5 turns out. I'm so confused. Please help! Thanks again for all the great advice!!!
 

Rick.

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Re: 1978 johnson 9.9 stalling on top end

Bummer. Did you try pumping the bulb as suggested? You should take a timing light and check for consistent spark on both plugs when you hit over 1/2 throttle. Hate to say it but you might need to clean the carb. again. Have you done a link and sync.? Check to see position of your throttle plate at full throttle. It should be wide open. Your a little wrong about it having a rev. limiter, it doesn't. What it does have is a device to not allow it to be started at too high a throttle while in gear. You need to look back at Daviet's post. It has CDI ignition so you may need to trouble shoot CDI components so checking for consistent spark is vital. Hang in there, you will get it eventually. In the mean time you can still use it to troll. Best of luck. Rick.
 

stratos201s

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Re: 1978 johnson 9.9 stalling on top end

Absolutely I will use it to troll! I still enjoy it very much for trolling......just would like to get places a little faster sometimes haha. Pumping the primer bulb does nothing at all. I tried it at all different throttle positions to no avail. You're right, teh device is to keep it from starting in too high a gear. Also it keeps the throttle from moving past half tho while in neutral. A link off the gear selector keeps the timing plate, which is directly connected to the throttle, from moving past about half. I will try to reclean the carb and verify the throttle plate position as well as double checking the cdi components. Just coil and wires right? Thanks again for the help!!
 

Rick.

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Re: 1978 johnson 9.9 stalling on top end

I'm not even suggesting checking the coils and wires at this point (although it's never a bad idea). These small OMC's run very smooth on only one cylinder. Spark is what you need to check. Spark on both cylinders. The normal complaint of a running on one cylinder engine is that it lacks power and top end speed, not that it is rough running. A timing light will prove spark consistency through out the throttle range. If spark is the problem there are things you can do to fix it but first you need to verify spark. Rick.
 

stratos201s

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Re: 1978 johnson 9.9 stalling on top end

Will do. I checked the spark plugs initially, but don't think I checked for spark specifically....just the condition of the plugs and replaced. The problem that leads me astray is that the motor literally bogs out completely as soon as you open the throttle past half or so...it shows no signs of loss of power....just like you gave it too much fuel all at once or something and it flooded out. Pulling the choke just stalls it even quicker. One thing I did try is spraying a spurt of carb cleaner in it at half throttle one the line where it's stalling and it picked up like crazy and ran full throttle for a few seconds then stalled. Primer bulb seems to be normal. Vent is open on fuel tank. 50:1 fuel/oil ratio. I will check spark and get back for sure. Also will check compression to verify readings. Thanks again for your persistance and patience!
 

OptsyEagle

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Re: 1978 johnson 9.9 stalling on top end

Well I would look at what differences there are between slow speed and high speed. Compression is needed for both, so rule it out. Spark is needed for both, so you can sort of rule it out for now. I would suspect the carb cleaner spray test (don't do that again by the way unless you mix some oil in it) would tell me the spark is working just fine and that leads me to what must be the problem. Fuel. Your carburetor has a slow speed jet and a high speed jet. You said you cleaned it out. Did you install a new jet and did you spray the high speed jet area with carb cleaner and blow it out with a lot of compressed air? Does the butterfly valve seem to be opening and closing correctly?

The next thing is did you align the carb to the timing plate? Does the cam follower (little round ball controlling the carb throttle) touch the throttle cam when the arrow on the thottle cam is in the middle of the cam follower?
 

stratos201s

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Re: 1978 johnson 9.9 stalling on top end

Thanks for jumping in on this! I can't thank you guys enough for all your help! I have such limited time with my job that I barely get to spend time with family/ do a little fishing so every minute I am working on the motor is eating away at both! I do love tinkering tho...but yes I did clean out the carb with cleaner and blow out all the jets with 110 # air. Couldn't hurt to do it again I suppose. The kit came with a new high speed jet which I installed. Butterfly is opening and closing fully. Also the choke operates normally too....kinda hard to mess that one up though. Very simple choke. I'm only somewhat familiar with the throttle cam. I believe that is the flat sorta shaped metal piece that rotates around the crankshaft area as the throttle is moved?? There is an arrow on it that points to what I assume to be the cam follower and it does in fact contact ( a plastic roller) that is connected to the butterfly and the arrow aligns when the throttle handle is at the start position....assuming that's the correct position. Is that what you mean by align the carb to the timing plate? Not really sure how to set up timing on it tho. I really hope this helps! Thanks again!
 

OptsyEagle

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Re: 1978 johnson 9.9 stalling on top end

That's it, all OK then. Hmmm quite a mystery.

The timing is set by the powerpack and timing plate where that cam is attached that moves the throttle. The alignment I mentioned just aligns your carb throttle level to the proper spark timing and it looks like yours is set well.

I have to assume your spark, along with its proper timing is working well because I assume that when you sprayed carb cleaner into the carb, at half to full thottle, that gave your motor the fuel it was missing and since the spark and compression were working well, off she went ... until this new fuel ran out. That is my opinion on that test and what it told. Maybe others will read it differently.

I have to assume it must be something with your high speed jet but with a brand new one in there and all the cleaning I am suspicious of that theory as well.

I am stumped. Perhaps reed valves or crankcase seals but I would be surprised that a failure of those would not cause you problems at idle and slow speed as well, so I am sceptical of them being the culprits, as well. Plus with crankcase seals, both have to be toast or you would probably only lose one cylinder, not both.

I'll have to think about this one, hopefully others will be able to zero in on it quicker for you. Good luck.
 

Haffiman

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Re: 1978 johnson 9.9 stalling on top end

..... I'm only somewhat familiar with the throttle cam. I believe that is the flat sorta shaped metal piece that rotates around the crankshaft area as the throttle is moved?? There is an arrow on it that points to what I assume to be the cam follower and it does in fact contact ( a plastic roller) that is connected to the butterfly and the arrow aligns when the throttle handle is at the start position....assuming that's the correct position. Is that what you mean by align the carb to the timing plate? Not really sure how to set up timing on it tho. I really hope this helps! Thanks again!

The arrow on the cam is the point where the roller(carb) should start touching and the carb should start to open. The cam itself is 'adjustable' to get this right.
A somewhat danger with older versions of this engine is that previous owners may have changed bits and pieces that does not quite match. That goes for cams and carb rollers mainly.
Be sure you have the matching parts:

http://www.marineengine.com/parts/j...=10854M&manufacturer=Evinrude&section=Magneto

http://www.marineengine.com/parts/j...er=Evinrude&section=Carburetor+&+Manifold
 

outlaw241

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Re: 1978 johnson 9.9 stalling on top end

is it possible you have the float upside down [not allowing enough fuel in at wot]
 

OptsyEagle

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Re: 1978 johnson 9.9 stalling on top end

I just thought of something. Probably not it but an easy test to rule it out. Have you tried running it without the hood on? If you have an exhaust leak, perhaps there is enough air to run at idle and lower speeds but as you run it harder the exhaust that may be leaking into the hood is starving your motor of air.

The next time you are out, run it without the hood and if it does the same thing, forget about this and if it runs fine come back and we can help you fix the problem.
 

stratos201s

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Re: 1978 johnson 9.9 stalling on top end

i installed the float like it came out which was how the picture showed...(thick side up) with the carb upside down and level with carb body
 

Will Bark

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Re: 1978 johnson 9.9 stalling on top end

I have a 1977 15hp Evinrude that was doing the same thing you are describing, bogging down at WOT; turns out that I had to set the float drop to the full 1 1/2 inch drop to keep enough fuel in the carb bowl. Will now run all day at WOT; maybe that's your problem. Good Luck!
 

kbait

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Re: 1978 johnson 9.9 stalling on top end

By spraying carb cleaner in the carb it took off (use mixed fuel as noted above). It's not getting proper fuel flow after 1/2 throttle. Pull the carb and remove the jet and inspect for debris. If clean, it really sounds like the float valve is closing too soon, and the fuel level in the carb bowl is too low to run solely on the main jet. Perhaps you have an extra washer on the 'seat' part of the float valve? Perhaps debris in the seat? If it's not obvious, pull the new sierra float valve you installed (needle and seat) and replace w/original (if you still have it), or a brp replacement and see if that helps. Sounds like you have the 'float is level w/inverted carb body' setting. Perhaps adjust the float so the non-tab side is lower to the inverted carb body, effectively increasing the fuel level in the bowl. Sounds like you're close.. hang in there! Good luck.
 

jmendoza

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Re: 1978 johnson 9.9 stalling on top end

To eliminate the carb, hook up an external fuel source to it, thereby bypassing the fuel pum, ansd see if that cures it. Of course, you will have to gravity feed, or pressure feed by continually squeezing the fuel bulb.

Anyway, you could have a bad fuel line, a leaky fuel pump(dried out diaphragms) hard and leaking fuel line at connector(sucks air) or the o rings in the fuel line connectors are bad. With an air leak in the fuel lines, it will deliver enough fuel to run at lower speeds, but starve for fuel when you try and go full speed.
 
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