'75 Johnson 9.9, need help determining problem!

[mp_2008]

Motor: '75 Johnson 9.9 hp pull start. Model #: 10R75C Well a couple weeks I bought this outboard motor. For the first week it ran flawlessly, started first pull, idled great and never stalled, and cruised up to speed without a hitch. Just recently I noticed that when getting up to speed, in the mid rpms it would, idk how to say it, make a muffle sound and then get right back on track as accelerating. Sometimes its quite noticeable and sometimes just barely. Now it will also make the same noise on occasion when it is first started. It still starts first pull and idles great and cruises and sounds great at full speed. When I first bought it, the guy said he cleaned the carb and it had new plugs so i tend to believe the carb needs rebuilt. Thoughts? Also, if i rebuild the carb, what else should I think about replacing since i have the carb off? The motor is in great shape for the year, original prop and like I said starts easy, idles great, and cruises at full speed. That muffle sound mid rpms just bugs me a bit. Any advice will be appreciated!

 

[mp_2008]

If need be, i could post a video/audio of what im talking about.

 

[OptsyEagle]

I wish I could help since my 1975 9.9Hp does the exact same thing. It starts great, idles and trolls fine but as I accelerate, about mid-throttle you get this, what I call, missing. As I accelerate more it smooths out. This miss happens at the same point whether I am accelerating or decelerating through it.

All I can tell you is what I know. I bought this motor about 8 years ago and I don't remember it initially having any problem mid-throttle. About 3 years ago I decided to pop the flywheel and give it a good tune up. I put on new points and condensers and adjusted the point gap to 0.022" (0.002" more since they were new points). Presto, I now have a mid-throttle miss. I popped the flywheel again and put on the old points, cleaned them up good and set their gap to 0.020". Mid-throttle miss was still there. I gave it a really good carb clean with a new rebuild kit and the mid-throttle miss remains.

Since the miss does not stall the motor and I have even ran it at that miss point for 60 seconds or so, to see if it will eventually stall the motor or go away, and it didn't, I decided to not worry about it. I have used this motor for a couple of years now with no problems except I don't like running at that mid-throttle speed, since as you said, it bugs me.

My going theory is this. When first popped the flywheel I checked the point gap on my points before I removed them. One was about 0.014" and the other was lucky to be at 0.002". It opened, but not by much. When I last used this motor I never really noticed any problem and it did not have a mid-throttle miss. As I said, I re-set the point to the specified gap and now I have a miss. So what I think might be happening is this. Over almost 40 years of use I have heard that these motor's flywheels can develop a small warping. This warping can effect the timing of when the spark fires in the cylinders. I suspect that when my points were at the 0.002" and 0.014" gaps, the retardation of the timing of my spark that this produced, overcame the warping of the flywheel or timing advance plate. When I then set them to the correct amount of gap, I did not have this amount of retardation of spark timing and hence at mid-throttle, one or both of my cylinders is now firing just a little before the piston is at top dead center (TDC) and creating the complaining noise or what I call a mis-fire. I have tried to correct this by adjusting my timing advance a little, where the throttle cam arrow will hit my carb'a roller a little before or after the proper spot. Maybe an 1/8" off the correct spot. This did not change anything with the mid-throttle miss. It does kind of tell me that my warped flywheel theory may not be correct, but I do not know how much 1/8" difference in setting my timing advance with the throttle cam might make, in comparison to my point gap being off by 0.006" and much more on the other cylinder. My guess is that the point gap change makes a bigger difference in when my spark fires then the throttle cam adjustment does and I can't adjust the throttle cam anymore or I might never have enough gas to get it started.

So for now, I am too lazy to pop the flywheel and reset the point gaps lower to test my theory. I did notice a much higher top end performance when the gaps were set at the specified 0.020" and I like that, so I figure, over-time the point gaps should slowly decrease on their own (as the rub bar wears down) and maybe someday I will notice that the mid-throttle miss went away. Until then the motor seems to work OK. If my theory is correct and one of my cylinders is firing before TDC, I am sure that is not good for it, but I don't run it at that throttle range for very long and I have 2 other motors like this one, all old and cheap.

Please let me know if you come up with some new information about this. I would love to get rid of the miss on mine if I new for sure what was causing it. My theory, like a few others I have had on this, is probably wrong. Good luck.

 

[mp_2008]

Hmmmm. Thanks for the info. What I dont get is why didnt it do it when I first bought the motor? Did it do it when the previous owner had it and he did something to temporarily delay it from reoccurring until after he sold it. If so what could he have done. Because like I said it didnt do it for the first week and I didnt touch the motor so these are question that are going through my head. Since he said he just cleaned the carb. Im thinking it needs a rebuild kit. Im relatively new to outboards but i get the feeling im going to know all about them while trying to figure this out.

 

[kbait]

If the armature plate (that the points ride on) has ANY lateral play, it'll directly affect point gap (and timing) and will run unpredictably. When you have the flywheel off, check for lateral play. If there's play, post back for easy fix. Once the play is gone, set points (filed up clean & shiny) at .020" and then you can test your motor, and rule out any variable spark timing issue.

If it were a warped flywheel, it would only change the magnet distance from coils.. possibly affecting spark quality, but not timing - and shouldn't change spark quality at different rpm's.

If your link/sync is correct, and your motor idles and runs wide open just fine, I'd rule out a fuel delivery issue for now, and focus on spark/timing. Use NGK B7HS plugs gapped to .030 as 9.9/15 Johnson/Evinrude '74-'76 (points motors) seem to foul champions rather quickly.

Good luck!

 

[OptsyEagle]

I am sure it is the armature plate's lateral play that I am talking about and not the flywheel itself. I can't remember if I gave it a good push to see if it had any play or not when I had the flywheel off. What is the easy fix if it does have lateral play?

 

[kbait]

Ok. First, pull up the schematic for your ignition system at boats dot net (where the 'dot' is a period). Check the schematic and read the following, and you'll be ready to go.

Armature plate is held onto the retainer (below armature plate bearing and support ring) by 5 phillips head screws. Loosen all of 'em and pull their threads up into the armature plate itself, which un-hooks it from the retainer. Lift the armature plate off the 'boss' at it's center (boss is on top of powerhead w/crankshaft going through it). Now, pull that plastic armature plate bearing off of it's holder (support ring) and set it aside. Place the armature plate back onto the 'boss' and check lateral play.. turn a bit and check again. If it moves laterally, what you do next will take up the slack space. Again remove armature plate and look at the 'boss' on top of powerhead. It's round, and the bearing surface is about 1/4" in height. Take a sharp centerpunch (or a screw, nail, etc) and 'peen' 4 spots halfway up the height of the sides of the boss at the 12, 3, 6, and 9 o'clock positions. What you're doing is making a little 'wave' of metal rise up around your punch marks, and that metal will take up the slack space between the 'boss' and your armature plate's center bearing surface. Start w/small 'peens', replace armature plate and check play (also, turn the armature plate to check for too much binding). If it still has play, peen the same exact spots again, and re-check play until there's no play left. Don't peen so much as to make the armature plate bind too much when turning(creates stiff throttle).. a little resistance is fine.

Now, reassemble. *The plastic armature plate bearing ring is dry fitted.. wipe all grease/oil off of that bearing, it's support ring, and the underside of the armature plate where it rides before reassembling*. Also, you can use needle nose pliers to pinch the bearing ends together for reassembly.

The 'boss' isn't a dry fit. I use white lithium grease on the boss (sparingly).

Set points to .020". Make sure they're filed-up clean and shiny (I remove the pointsets, disassemble, place each point 'face' aiming up in a vice, and use a file to gently remove pits/dirt. I then use a dull file to make the faces shiny-new, then a points file to slightly bevel the edges before reassembly).

Now, you'll have no more lateral play in your armature plate, and your timing will not jump around w/changing point gap that it caused.

This fix will last a long time, as the peened metal you raised is lubricated, and only moves against the armature plate when you turn the throttle handle. I've used this technique several times for customers with 9.9/15hp points motors (and many times for other points motors), and never had one come back w/lateral play issue.

Hopefully this will fix your mid-range issues.. if not, at least you can be assured that your timing isn't jumping around.. and again, NGK B7HS @ .030 for these motors.

Good luck!

 

[OptsyEagle]

Thanks kbait. I will take a look at that. Is this lateral movement something that can be observed when the flywheel is still on?

 

[mp_2008]

Well. I went out last night and when I first started it, it misfired a few times before evening out to a nice idle. Earlier in the day I did go out and tinker with the fuel to air mixture nob and making it run richer than what I usually ran it at. I left it that way until after i started it last night so I dont know if that has something to do with it. But I was just looking over the carb. And there was gas a bit of gas on most of it and I noticed a decent puddle under the carb pooled up. It actually looks like the carb has been rebuilt recently and the fuel pump replaced. Gaskets on the carb. look new as does the fuel pump. Any thoughts as to the cause of the puddled up gas?

 

[kbait]

Yes, Optsy, you can check the armature plate for play w/flywheel on. Check it, turn flywheel 1/4 turn and check again etc. The flywheel magnet will pull on the charge coil when it's oriented that way, and it's harder to feel any play, that's why you turn flywheel a few times while checking.

 

[kbait]

mp.. pull the air silencer off the carb and squeeze the primer bulb to see if any fuel comes out carb or fuel connections. If not, and the inside of the silencer has fuel in it, you may have a leaf valve(reed valve) not seating and letting fuel blow back, out carb front. If that's the case, it likely would not idle well.

 

[mp_2008]

Hmmm. Ill check it out. I talked to the previous owner and he said he never had the carb rebuilt or the fuel pump replaced so im going to rebuild the carb. I was told the original float is made of cork and they tend to degrade and clog the jet but i have a feeling it has been replaced sometime in its past but im rebuilding it regardless, only 35 dollars for the kit with the two gaskets, jet and misc. Was wondering if I there is anything else I should replace that doesnt come in the kit while I have the carb off? Also, i was out in the boat tonight and noticed something else. It started first pull, had a few misses in about a 10 second span right after start up and then idled out nice. The thing I noticed though is after I took a trip across the lake, sat for a bit and started it up, it idled nice but while i was in neutral i revved it up and at high throttle it would make a quick but short knock sound like it was missing or something. A completely different sound than what I would call misses at first use of the trip start up but it sounds like a true miss. I wonder what would be causing that. I am going to check compression here soon and am going to buy a timing tester here quick. I was going to give you a link to the site with the carb kit so you could possibly let me know if there is anything else I should replace but I cant get the link to go to the specific page and I cant get rid of the link to the main page below for some reason so you can just ignore that.

 

[OptsyEagle]

Most carb kits will come with everything you need. You should note that inside the slow speed jet is a little funnel looking bushing that needs to be replaced. It is almost impossible to see when looking inside the jet, but it is there. Getting them out is always a challenge. I have used a #8 deck screw in the past and very carefully turned it in a turn to bite onto that plastic piece. The danger here is that steel screw could really do some irrepairable damage to that aluminum carburetor so don't turn it too much. I heard a better idea that I haven't tried yet where a guy took a fish hook and straightened it out and used the barb of the hook to grab onto that plastic piece. That did sound like a safer method. You also want to remove the welch plug on the top of the carb and clean in there really good. That mid-throttle miss that I have seems to happen around where the slow speed of the carb changes to the high speed and perhaps, if it is a carb problem, it might come from there. I use a small drill to drill into the welch plug. Don't let the drill bit go into it much more then the hole you make, since about 3/8" below that welch plug is carburetor that will not like a drill bit either. I then just pull the welch plug out with something that fits in the hole. I can't remember if the carb kits come with a new float or not. I would recommend changing out the old cork floats, if you can. The link you posted is to a competitors site so I think the techies here have done what they need to do to prevent you from sending them their customers.

I cannot comment on the knocking. As for the missing when first started up. That motor does not necessarily jump to attention when started up. It tends to complain about it a little more then other motors I have used, but once warmed up it is very dependable. So I wouldn't worry too much about missing in the first minute or so of running. Also, I can't remember if you have re-set the slow speed jet or if it is still 2.5 turns out. If it is still 2.5 turns out, the motor is probably going to complain a little about that. You should set it correctly with this method.

http://forums.iboats.com/forum/engin...eeves?t=167352

 

[mp_2008]

Wow, thanks for the tips and the link. Very very helpful! The kit I have coming does come with a float. Didnt know Iboats sold parts, etc. Just found this forum by researching using google. Sorry Iboats, didnt mean to post a competitors link. Feel free to remove it.

 

[OptsyEagle]

Also, they now use a small spring clip that clips the inlet needle to the float arm, that you will get in your carb kit. The new inlet needles use a rubber tip that seals off the fuel better then the old design but can sometimes stick in the inlet canal. The spring ensures that the inlet needle opens up to allow fuel to flow when the float drops and the new tips ensure the needle shuts off the fuel when the float say your carb has enough.

I mention this because, depending on how long ago your carb was last cleaned, the needle you remove from it may or may not have this clip attached. You want to ensure that you do attach the clip to the new needles. It is easy to do. One end clips onto the end of the inlet needle and the other wraps around the arm of the float.