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1975 Johnson 9.9HP Project

ebacon

ebacon

Contributing Member
Hello all,

I bought a 1975 Johnson 9.9 HP that needs a little work. It will go on a 12' aluminum V-hull. The engine runs and appears to have a new carb. I started this thread to document the project and look forward to getting to know you all in this sub-forum. I will attach a few photos of the engine later. I forgot how to use the forum software. :D

The engine needs:

1) a new prop shaft seal
2) a new fuel line between the filter and carb
3) realignment between the indicator mark and associated positions (START/SHIFT, etc) on the twist tiller
4) Once the engine is running fine I would like to fix its cosmetics. It's a bit rough looking.

I read through the forums and it appears that some 9.9 and 15 HP engines are the same except for the carbs. Can my engine be upgraded to 15 HP? All of the examples that I saw of 9.9 HP being upgraded to 15HP appear to be dual carb engines. My engine has a single carb.
 
1974-1976 9.9 & 15HP motors were not too well loved by some people (including me). They were notorious for fouling plugs. That's probably why it has a new carb, among other factory fixes which didn't work. Beware.
 
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https://www.apba.org/documents/999566626-04132020-JUNIOR rules4.10.20.pdf

Page 11...

see hole "P" in water tube is needed for the meg tuner aimed at the top motor mount for cooling.

See holes D1,D at mids bottom for use with the meg tuner. Turns exhaust into a "folded horn" exhaust designed by westcoast.

Use newer head, top thermos, with no cooling jacket around plugs for a no foul plugs idle. Never fouled a plug even with the energy transfer ignition on my '76

If ya want real power...Do the "D" cut behind the liner...that's where the power is at. 7450 with 4b10p prop

As always see Leeroys site.
 
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Hello ebacon! Looks like you have the same 9.9 as me. Mine is a 75 as well. I am going thru mine along the path to make it a 15hp. I am doing a few extra's just because I like to tinker and experiment. I had a few issues with mine when I picked it up last year. Figured them out by years end. I had a monkey'd up carb. Was dirty inside, plus somebody tried to remove the non-removable brass tube beneath the high speed jet. It was all bent up and such. Also I had a BO cracked fuel pump that would seal when cold, but once it got hot it would expand and the engine would run lean without the choke on.:(:(:( I can't speak for the fouling of plugs, but then again I only had it running right at the end of the year also. I have nosed around here and researched a few paths from Timguy, Sunkinmess, Racer, Flyingscott & Fdrgator, aswell as phone calls to people that build outboards for racing, to build mine up. Let the questions flow, and you will get your answers. A lot of knowledge here.:cool:
I did find from chatting with Sunkinmess that the newer Cyl heads with the t-stat up top helped with the fouling issues due to there being less cooling water around the spark plugs and helped change the t-stat if you ever needed. Will probly change mine when I get to parts shopping. I do have a thread going about my 15hp adventure. Is maybe 1-2 weeks old. "Hot rod 9.9 build up". ok, enuf, I won't snipe your thread.:cool:
 
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Mods, could you delete just this post? It double posted along with a bunch of background script.
 
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Gator, yes they have their weak points, but I have learned to love the "breaker points" models. To prolong life, reduce carbon, clean up operation overall, I have ALWAYS used Amsoil 100:1 premix at ratios between 64:1 and 100:1. I never, ever condone or allow ANY of my motors to use ethanol, or any alcohol additives. Most readers here know my story. I have operated 2 remote camps in NW Ontario on pristine oligotrophic "drinking water" lakes. Customers come here and don't want to breathe smoke from their outboards. I was introduced to Amsoil by its founder, Al Amatuzio, who was a good friend of my parents. He gave us a case of the 100:1 to try at our camp on Lower Manitou. This was in the late 70's. The marks on the tiny bottles are one unit per gallon, with each bottle to lubricate a 6 gallon fuel supply. We had a few 15 horse OMC's and several other motors from the 50's and 60's. It has now been 45 years and all but one of these motors are still in my possession and still run beautifully. I sold the 16 horse Evinrude Fastwin, maybe 20 years ago, and it still ran great......so I'm not just "blowing smoke".
A huge problem with this series of 9.9/15's has been too much oil......resulting in motor mount failure and excessive carbon buildup.....including fouling of spark plugs. Ethanol fuel has also contributed to the deterioration of the motor mounts, as well as any rubber components like hoses, diaphragms, and seals. Your motor has had a newer style, longer tiller handle swapped, which is a nice mod for certain boats. The prop seal may not be the source of that leak we see, but it could well be the drainage from the exhaust housing of old oil/gas, and carbon. Overall it appears to be in very good shape, except for the cosmetics.
First do a compression test, then drain and pressure test the lower unit. Don't forget to turn shafts, and operate the shifter while 13 psi is applied. This will mimic real operating conditions. If more equipment is available to you, then apply a vacuum tester while operating moving parts again.
More later....gotta cut some chicken up for dinner.
 
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Life experience can be so different for 2 people. I have ran 25/1 in mine since '16 and it only has a wisp of blue at startup and is gone 100 yards from the dock. Gorden Jennings did a thing on it many years ago. Interesting study on oil mix. I did make polyurethane mounts for it so oil is a non factor.

My shift shaft oring leaks some on mine. I have been using Loctite 105 for lower lube for 3 years with magnetic plug. I am never going back.

The newer head with no water jacket over the plugs solves the plug fouling issue no matter the oil mix.
 
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We troll for hours on end at 2 mph for lake trout. 24, 40, 50:1 would kill us. 4 strokes are too heavy to carry across portage's. 15's can be carried easily on your shoulder, and still pack a punch to cover many miles in a short time. Guests love the 15's. There is no plug fouling at 100:1....one set lasts the whole season, often even 2 seasons.
 
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I have found that there is a lot of throttle per unit advance on these motors. It seems the oiling needs outpaces the combustion needs at low speed. So the motor passes a lot more fuel mix with retarded timing. So I took a crap load of ramp off the throttle cam using the 25/1 mix. So I ended up with the same oil at 50/1 with much less gas going the motor from idle to 3/4 throttle. It runs very clean at low speed but has the full 25/1 at 7450 rpm.Hence hardly any smoke with 25/1. But one cannot go back to 50/1 now....
 
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Post # 13 needs a bit more explaining.-----What does retarded timing have to do with fuel going straight from intake ports and out the exhaust ports.----Post #13 makes no sense at all.
 
look at the etecs..direct injection with oil and air through the case only. The oil mix motors at low speed have a lot of throttle opening per unit timing advance. In other words a lot of fuel at low speed with retarded timing so it will run clean without 4stroking. With 50/1 gotta be careful not to have too much advance at low speed or one can burn up the motor. So I run 25/1 with half fuel mix passing through motor until 3/4 throttle. So at 2mph my motor has more timing advance with a lot less throttle than stock and runs much less fuel cause it rums more efficiently without burning up from lack of lube.
 
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Look at the fuel delivery curve for the etec. much less fuel at low speed with a lot more timing. One cannot run that fuel curve with the oil mix motors. On the etec the combustion needs and the oiling needs are separated which is one reason why it passes epa...also direct injection the fuel amount is controlled so it does not just blow through the exhaust like on a mix motor. There is no power valve on the exhaust port to handle this.

Just don't say wow..explain yourself if I'm wrong..


Look at a drag motor with 28 degrees fixed timing. No good as a fishing motor cause with that much advance..efficiency.. there needs just a small throttle opening per power output that the oiling needs are not met at low speeds.
 
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Thanks for all the info. I ordered the factory service manual and should have it in a day or two. I want to thumb through it before I start turning wrenches.
 
Reading through the preceeding posts, there have been many concerning fixes for the early 9.9 motors to make them run. The original factory service manuals will not mention any of them. In fact, I have never heard of some of them myself. I was a tech in an Evinrude dealership at the time and my experience is limited to the motors when brand new or nearly new and would not run one weekend. AND the factory warranty fixes that did not work. I would recall the motors and install the fix kit and the owner would pick it up on Friday and bring it back on Monday morning. They left such a bad impression in my mind that remains to this day. Congratulations to you guys that figured out a way to make them run. I simply do not mess with them any more. That fixes them for me.
 
Ha.....great, Gator. The mods I suggest are very subtle.......but make a huge difference. I completely rebuilt a 1974 5 or 6 years ago, sold for $1,500...gave the guy a ten year warranty. After the first year, he only had to buy the parts, (first year was free, parts included).....my labor would be free. If anyone else worked on the motor, it would void my warranty. He had to use Amsoil 100:1 pre mix at 100:1 with non oxy fuel......I gave him a quart. Told him I wanted it back every year for free check up. Guess he musta dropped the motor in the lake.....never heard from him again. My phone number is engraved on the flywheel.
 
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Made a lot of progress the last few days.


  • Compression check is 100 PSI for both cylinders.
  • The fuel line between the pump and carb was worn through and leaking.
  • Lower unit lube was contaminated with water. Propshaft seals are shot but bearings look good and no corrosion inside.
  • Carb is a 9.9 HP model.
  • Ordered all the typical parts from MarineEngine.com. Lower unit seals, water pump kit, carb kit, ignition kit, gaskets, fuel pump parts, fuel line zip ties, and a handful of gaskets.

I have a couple of questions:

1. Do any of you know where to get Johnson green paint (1975) in a rattle can for the lower unit?
2. Does MarineEngine.com send a confirmation e-mail for an order? I did not get an e-mail. Worst case I will call on Monday to make sure they got the order.
 
Not sure on your order confirmation, but my auto body supply store mixes my paint for me. They shoot a section of old paint and mix for you. That way it will match in case I'm not painting the complete motor. I do have the formula for that OEM sea horse green. You would need a spray gun and a little compressor. You probably have a compressor already. You can get decent guns for around 50 bucks. That way you can do an epoxy clear coat afterwards.
 
Thanks for the info regarding paint. I have a compressor and spray gun but have not sprayed since the 1990s. At this point I am thinking that getting the engine mechanically sound is more important than appearance. I was hoping for a rattle-can paint source.

Back to the mechanics, all the parts have arrived. Today I washed the gearcase and noticed that I did not buy the O-ring for the shift rod. I have a small slide hammer to remove the old one. My worry is putting in a new O-ring. What is the diameter of the Bushing Installer #304515 that the Johnson manual suggests? What do hobbyists use when they don't have the tool?

The feel of the old O-ring/shift rod interface feels watertight so I don't want to replace the O-ring if I don't have to. Replacing that little bugger seems like trying to tie a knot in the bottom of a balloon.

The O-ring is #25 in the photo.

ORing25.jpg
 
Good. I have a tool that is actually a piece of small pipe, that way you can "set" the bushing while shift rod is in place. Why? If there is too much "crush" on your o-ring, it may become actually TOO tight. You should "set" the o-ring only until there is "moderate" pressure to seal onto the lubricated shift rod. If you drive the bushing too tight and "crush" the o-ring, you may damage it when pushing in the shift rod. NOTE: Make sure shift rod end has no burrs on it, that could injure your new o-ring.
 
Nice idea Tim. I woulda done the "tap and check method" back and forth till I over did it:rolleyes:. I will have to remember this.




timguy said:
Good. I have a tool that is actually a piece of small pipe, that way you can "set" the bushing while shift rod is in place. Why? If there is too much "crush" on your o-ring, it may become actually TOO tight. You should "set" the o-ring only until there is "moderate" pressure to seal onto the lubricated shift rod. If you drive the bushing too tight and "crush" the o-ring, you may damage it when pushing in the shift rod. NOTE: Make sure shift rod end has no burrs on it, that could injure your new o-ring.
Click to expand...
 
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