1982 Johnson 9.9 random RPM fluctuations at full throttle

[jwall55]

Hello,

First time here, not a mechanic by any means but enjoying tinkering on my outboard and have a few questions. I have a 1982 Johnson 9.9 (J10ELCNS) with electric start and remote steering console setup on a 15 ft. Gregor, boat starts right up nice and easy but I am having a couple different issues that I think are most likely related to the same root problem, hoping for some advice on best places to start digging around in the engine.


1. When running at full speed, it always seems as though (just a gut feeling) that the engine is not putting out 100% of its power. I feel like there should be more there, but giving it full throttle it seems to underperform.
2. Sometimes (completely at random) when running at full speed and without me doing anything at all, the engine will fluctuate in RPMs as if I was moving the throttle up and down. It fluctuates up and down rather quickly, about a second between each fluctuation - up, down, up down. And will eventually land back into a smooth (regular) running RPM. This happens completely randomly. I could cruise around the lake for an hour no problem, then all the sudden up, down, up, down, etc., and then it goes back to normal. As a note to point #1 above, even when I have the boat in full throttle and when the fluctuations have started, the RPMs have even gone up from where I already was (was already at full throttle), hence that leads me to believe there is more power available somewhere, but something is preventing that from being fully realized.
3. Almost same as above, except for it will be running just fine, and then all the sudden sound like it flooded and/or gas was shut off and kind of putter out and die. I'll have to wait a few minutes before trying to fire it back up. But once I do, fires up and runs.

Reading up on this today it seems a couple things that may be causing these issues probably fuel/carb related. I took a look at my engine and noticed a couple things -
1. My carb seems to have a couple spots on it where it appears to be gunked up, maybe seeping through? Not sure what it could be but it doesn't not look right to me. See the pictures where the two spots have like grease/oil on them. Right to the left of the choke lever in the picture you can see grease/oil/gas spot or something, and the same thing in the top left of the picture.
2. The serial number stamped on my carb I cannot find anywhere. Not sure if that is something to be concerned with or not. Number on there is 390049. You can see this in the picture also - it?s very light but I can assure you those numbers are 390049, and it?s not listed on the parts for this engine or any that I could find really.
3. I noticed the cam follower and cam follower roller has some grooves worn in it, and had read online that that could be causing some of the throttle/full power issues.
4. I also read that there could be a small hole/leak in the fuel line somewhere which would cause it to sometimes get too much air and die out as mentioned above.
Anyways these are the issues I am having I welcome any and all thoughts as I work these out, thanks so much!
Jake

 

[racerone]

Run with a timing light hooked up and see if there is an ignition problem / miss.

 

[jwall55]

Thanks, how would I go about this if the fluctuations occur at completely random times? I'm new to the more "advanced" things like timing lights, etc. Thanks again

 

[oldboat1]

sounds like a carb rebuild might solve the problem, and probably due anyway. Lots of discussion about 9.9 vs. 15 hp carbs, but good idea to just rebuild the one you have on it (same kit for either hp).

 

[jwall55]

Thanks, I was probably going to do that anyways, for peace of mind and to learn how to do it. Also, just now thinking that it could possibly be an altitude thing? Live at about 500ft above sea level, and the lake I am cruising on is at about 5,000 ft elevation and from what I am reading engine would run rich at that elevation and would expect to lose power, about 20% (maybe has to do with point #1 above?). Could this be the reason for the engine stalling out/low performance?

 

[oldboat1]

interesting. Think altitude wouldn't give you fluctuations, though. More like running smoothly but lack of power. (The experience I had with our old Oldsmobile, anyway....)

 

[tomhath]

Are you sure the vent on the tank is open?

 

[jwall55]

Oldboat, the lack of power is just a gut thing... And I know my buddy has mentioned changing pitch at different altitudes but not sure for a 9.9 that really matters. I might try and take it out at sea level this weekend and see if there is a noticeable difference just for peace of mind on the topic of altitude/prop. But the fluctuations are a different story.

Tomhath yes the vent is open for sure, I know because it's missing

 

[oldboat1]

Well, think there is a good chance that solving the fluctuation problem will also resolve power questions. I?m more comfortable quickly going through fuel system repairs, as opposed to CD system troubleshooting, and that?s probably why I think of ruling out fuel issues first. But you may end up doing both ? and getting a good running motor at the end.

I bought an ?83 Yachtwin for use this summer, and a couple of 9.9 parts motors as well (?84 Yachtwin and ?91 9.9 electric). Turns out they are all good runners now, so I got a little lucky. I did a lot of switching CD components (including a flywheel) along the way, mostly trying to troubleshoot the ?84 ignition. I ended up replacing a flywheel (dead magnet), a sensor and charge coil. I was working from a no spark issue (lower cylinder), then weak spark. The bad flywheel magnet caused the no-spark, and the sensor/charge coil was apparently the cause of the weak spark (not sure which, finally ? replaced them both). I also rebuilt all three carbs along the way.
So based on what I found, I guess I would check for a strong spark first. The CD system puts out a powerful spark when working right ? easily a half inch plus on a tester. If you don?t find a problem, look for fuel issues (cracked hoses first). Check the fuel pump output at the carb, and rebuild or replace the pump if necessary. If the pump is OK, rebuild the carb ? or maybe just rebuild the carb anyway while you are at it. (You probably know all this stuff.)

If you still have problems, you might indeed have a stator or power pack issue affecting, say, timing at higher rpms ? or perhaps a coil cutting out when the motor is hot. I think the stator for your model is expensive, although you might be able to substitute. Power packs aren?t all that expensive, along with mid-?80s stators (or coils) ? worth it, in my estimation, if your motor is otherwise in good shape.

It?s nice to have parts motors for testing components. I managed to do some analysis using info from a couple of internet sites (e.g., ebasic). But finally I was switching out components.

 

[jwall55]

Thanks for the details oldboat, really appreciate it. Actually I don't know all that stuff already - I pick up quick but never worked on these much before, having said that couple questions back for you. How do I go about checking for strong spark? I will check all hoses and fuel pump, pump looks rather new however. I was thinking of rebuilding the carb anyhow for my own knowledge/peace of mind - plus as it looks in the pictures I don't think that gunk coming out of the top of it looks right anyways hahah. Ill check the spark, fuel lines, carb and see what that does for me.

 

[oldboat1]

Buy an adjustable spark tester at AutoZone or NAPA and set it for a half inch gap or a little more. Pull both plug wires, and plug in the tester like you would a plug. Clamp the other end of the tester to an engine ground -- needs to be securely clamped, and a spot where you can view the tester. I don't ground the other plug lead, but I've seen others advise that. On my 9.9s, I use the electric starter to crank. Repeat with the other plug lead. If no spark, or light spark, reduce the gap and test again. If you get down to, say, 1/4 inch or so before you get spark, you have a weak spark (good news and bad. have spark, but too weak). There is a lot of expert advice here on ignition issues (CD troubleshooting too if you get to that).

Can work backwards from the carb when working on the fuel system (fuel line cracks on old hoses are typically around pump or carb nipples, base of clamps, etc. ) need to bend the hose a little at clamps to make sure it's flexible, and to reveal any cracks. If it breaks, it was probably ready for replacement anyway. Check that large line going around the back of the pan to make sure its not kinked or jammed.
BTW, the t.stat is a bugger to get at as it sits down at the bottom rear of the pan, blocked by the latch. It's just really tight. If you get to that, remove the cylinder head, then [FONT=Helvetica, Arial, Verdana, sans-serif]unbolt the t.stat cover. To put it back together you will need a head gasket and a gasket for the t.stat cover. I have some difficulty getting a good seal on the t.stat gaskets. The bolt pattern was improved in ?84 and that helped. Putting the t.stat at the top (as in the ?91 I have) is a major improvement. Guess I would suggest not fixing it if it ain?t broke (i.e., cooling OK).[/FONT]

[FONT=Helvetica, Arial, Verdana, sans-serif]just happened to have tinkered with a couple of those recently -- getting wordy. sorry. [/FONT]

Get some parts diagrams either in a manual or online, and go from there.

 

[jwall55]

Thanks so much really appreciate the help. I'll check spark, fuel lines and carb and let you know what I come up with!

 

[jwall55]

Oldboat, ordered my fuel pump and carb repair kits, will probably get to that this week. When setting back up, would you recommend a fuel filter as well on the line before coming into the fuel pump? I can see on the fuel pump diagram for my engine it lists a fuel filter, but doesnt really show where it goes exactly. And looking around online I don't really find a lot of information on where people install them on these older outboards, or if they have them at all. I see a few of the larger canister type fuel water separators people use on larger engines, and some inline fuel filters, but info seems kind of sparse on if/how to use these.

 

[racerone]

These motors all left the factory with a fine screen in the cap that screws on to the pump.-------That is all you need.

 

[oldboat1]

+1. If a chance of water in the fuel tank, empty the tank and start over. Fresh gas.

 

[jwall55]

Just got back from quick trip this morning at near sea level, she ran great! A bit quicker, a bit faster and none of the engine issues I was mentioning. I haven't touched or checked anything yet wanted to see how it ran at sea level first. Not sure at this point if I want to mess with fuel pump and carb or leave her be. At this point it might be safe to say it was just the altitude