1990 Johnson 200 - won't idle after 20 minutes of running

[groundloop]

This is an engine I purchased on ebay (NEVER AGAIN !!!) to put on a boat I was rebuilding. It's had multiple issues which I've fixed one at a time, but this latest has me stumped.

It's done the same thing to me the last two trips to the lake - starts up ok, idles out of the no-wake zone ok, run around for 15 or 20 minutes with multiple stops and starts including a few WOT runs - still ok, and then all of a sudden it won't stay running at idle and bogs coming out of the hole. To keep it running at idle I have to keep my foot in the throttle, and even then it idles really rough and frequently dies out (make it real fun putting the boat on a trailer at a crowded ramp!).

It has a new CDI power pack and new CDI timer base (which I re-tested this weekend per OMC service manual procedures and they check out ok). The stator charge coil resistances are 734 and 767 Ohms (spec. is 985 +- 25 but I'm thinking the difference may be because I'm using a Fluke and not an analog meter - feel free to disagree with me), and the charge coil cranking outputs are 183 and 188 volts (measured with DVA adapter), spec. is 130 volts minimum. All 6 coils check out ok on the resistance test.

edit to add: I put in all new spark plugs before the last trip to the lake and pulled them when I got home. They all looked the same, insulators were slightly brown - about what you'd expect.

What am I overlooking? Thanks in advance for any and all expert advice.




Modified by groundloop at 8:13 AM 5/2/2011

[toddgot5fish]

sounds like an issue that only occurs when motor is at running temp. did you take all your measurements when the motor was to operating temp???

[groundloop]

No, all the tests were done with the engine cold. It's definitely worth a try.

[ChampioNman]

Did you ever try and hit the choke to see if it helps? If the motor picks up at the time of the fault then you have a fuel delivery issue. If not then it is electrical. You may want to pull the pickup tube out of the tank and see if it is clear and not some debris getting sucked up then when the motor conks out it falls away from the pickup. You could always hook up a portable tank and try that too.

[groundloop]

Yes, tried hitting the choke once or twice, no help. There are several reasons I don't think this is fuel related (anyone that has a different opinion please feel free to tell me I'm wrong). First off I totally rebuilt this boat last year - the aluminum fuel tank was pristine inside, I installed a new pickup tube, I've got all new fuel lines, and a new Racor filter/separtor (and there's zero sediment or water in the bowl).

Now, with that being said, I can't rule out the fuel pump because I've never actually tested that, but even when it's acting up once I get the boat up on plane it seems to run more or less ok.

[ChampioNman]

Let's try some steps here: Is the idle timing set correctly? Have you tested the recirc valves? Clogged or bad recirc valves will give poor idle characteristics. Idle timing improperly set will also give you fits. The timing needs to be set in the water with a timing light. Is the sync n link correct? Throttle plates opening and closing fully?

[groundloop]

I did the link-n-sync exactly per the factory shop manual. Recirc valves are all nearly new - someone before me had just installed plain hose barbs so I removed those and put in 6 brand new recirc valves, that's been about 2 months ago now (like I said, this engine's had a lot of issues).

Idle timing is pretty darned close, as close as I could get it with the engine in a tank. The thing is - it seems to run fairly decent for a while, if the timing were off wouldn't it run crappy right from the get-go (at least after it warmed up and came off of fast-start)?

[red devil]

Not that I'm expert but my motor was running almost the same way you describe. You might wanna take a look at the main jets. Mine had been drilled out. They had the proper numbers on them but when checked with go-no go pins it showed they had been drilled out quite alot. A new set of jets from BRP and now it seems to be lots better.

[groundloop]

I've been busier ther past few days than I thought (wife had minor surgery, since she was down for a few days I was busy running kids around etc.) so I haven't had a chance to do any more work on this engine. Also, thanks everyone for responding - I've learned a good bit in the course of getting this engine going but will readily admit that I've still got a lot to learn.

ChampioNman, I'll definitely check over every last detail of the link-n-sync, engine timing, etc. I'd be thrilled to find out that the entire issue is my screw-up on a simple adjustment. Is it possible though for one of those problems to only cause problems after 20 minutes or so of running? I'm not arguing, just hoping to maybe learn something.

Red, are you saying that with your messed up jets that it ran ok for awhile first and then acted up? I'll take a look at that if I don't find anything else.

Todd (how come you only caught 5 fish? ), thanks for the suggestion (I probably should have thought of that but sometimes in the heat of battle I overlook the obvious).

Here's my plan of attack. I've got a small tank I can dunk the lower unit in to get pretty close to actual operating depth. While the engine runs at a fast idle, every few minutes I'll take DVA measurements of the coil primary voltages (orange wires), check spark on each cylinder with my timing light, and also keep an eye on engine timing. While that's going on I plan to also add some heat to the coils one at a time with a hair dryer to see if I can get one to act up. After 20 or so minutes of this I'll shut it down and repeat the ignition system tests from the service manual.

Have I missed anything?

[toddgot5fish]

one tool i do suggest you purchase is a piston stop tool . they have them on ebay for 15 shipped to your door. my reading of TDC was off. the tool showed my messed up reading to be about 3 degrees off, which makes a big difference at idle.

[groundloop]

I checked the timing pointer, it was only off by 1/2 degree.

This ordeal is getting frustrating . Sunday evening I ran the engine in a tank at a fast idle for about 20 minutes then did all of the ignition system checks and everything tested good. I put it all back together, ran the engine some more once it got dark and looked for any sparks between coils or plug wires and a ground, nothing.

Last night I re-re-checked the timing and link-n-sync and it was all still ok. I looked for any sign of fuel/air mixture being spit out of the carbs to indicate a bad reed, didn't see anything. Then I tried adjusting the idle screws on the carbs, but it was really difficlut to see any difference just idling in a tank while trying to read the dash mounted tach. Right as I was making the decision to hang it up for the night the engine quit. I restarted it and as soon as fast-start turned off it died again. Restarted, and it took a lot of throttle to keep it running, that's exactly what's been happening at the lake. So.... I guess that might be viewed as progress.

One thing that has me scratching my head - I'd mentioned that prior to my last trip to the lake I put in new spark plugs, and that they all looked the same when I checked them back at home. Sunday night after sitting there idling for 20 minutes I checked the plugs again, all the plugs from the starboard bank were very clean, and all the plugs from the port bank were black. (I've measured head temperatures with an IR thermometer and they're all between 140 and 150 at idle, right where they belong.)

As always, if anyone has suggestions or expert advice I'm all ears.

[groundloop]

OK, I was workig on it more last night, ran it at fast idle 'till it started running very poorly again and checked spark on all cylinders, everything was ok there, so not an ignition problem after all. I finally happened to notice flame from a backfire in #6 carb. It didn't happen often, just very intermittently.

Anyway, it's progress, right? As mentioned previously this engine had a lot of problems when I got it, so a lot's been done to it. It has rebuilt carbs from a '96 200, so I'm not thinking a carb problem is very likely. I drained all the carbs just to see what I could see, they all had an equal amount of fuel and it took a good 3 - 4 seconds for each one to drain (so I believe all the carbs are getting enough fuel and that float level's not an issue).

No amount of adjusting idle screws made it any better. Also, while it seems to run more or less ok when first started, it's still not what I'd call a smooth idle.

So now what possibilities are left? Here's what I see as options:

Air leak somewhere after the carbs

Bad lower crankshaft seal If this were the case would there be anything else to look for? (I've already replaced the upper seal because I noticed it was leaking fuel/oil).

Reeds (???)

Thanks.




Modified by groundloop at 11:28 AM 5/12/2011

[THE WITCHDOCTOR]

My money is on the reeds..... Probably when you get it tore down you will find the rubber coating is charred or broke reed.....:)

[Melton Jason]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by groundloop &raquo;</td></tr><tr><td class="quote"> I finally happened to notice flame from a backfire in #6 carb. It didn't happen often, just very intermittently.[/i]</td></tr></table>

That really sounds like a reed issue. You should be able to just pull the carbs off individually, open the throttle bodies and see most of the reed cages to inspect them.

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by groundloop &raquo;</td></tr><tr><td class="quote"> It has rebuilt carbs from a '96 200, No amount of adjusting idle screws made it any better. [/i]</td></tr></table>

Does the 96 model have idle screws? cause the 90 model doesn't. They are fixed jets.

[groundloop]

I pulled the reeds last night. On nearly all of them I can see a sliver of light around the edges, and on one individual reed on #6 there's a gap that's maybe the thickness of a couple of business cards. There are no visible signs of damage on any of the reeds.

Yes, the '96 carbs have one idle screw to adjust.

[THE WITCHDOCTOR]

They should all be flat... No cracks?

[groundloop]

I've read about guys just flipping over these steel reeds, is that truly a fix or is it time to just bite the bullet and get new ones? (I'm just as cheap as the next guy).

Also, if I do really need to get new ones, are aftermarket reeds (Boysen or Chris Carson Marine for example) going to be give a noticeable improvement over stock steel reeds? I honestly don't NEED more top end (though I'd never complain about more speed), what I'd like is to have a really smooth idle and better hole shot.

Finally, does anybody know the factory part number for these reeds? All I can find is a part number for the complete reed box assembly (at over $100 each x 6 - OUCH).


Thanks

[THE WITCHDOCTOR]

I think you will have to replace the whole box, but dont quote me on that. As far as the aftermarket, no speed gain, and if it leans spits sooner or later you will be putting a reed in it. Not for sure on the flipping upside down part.

[Melton Jason]

I have read not to flip them over that they will stress and break, sending lovely metal parts through your engine, From what I have been reading most are putting CCM reeds in them.

[groundloop]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by 89 hydrasport &raquo;</td></tr><tr><td class="quote">I have read not to flip them over that they will stress and break, sending lovely metal parts through your engine... </td></tr></table>

That makes sense.

Guess I'll get some CCM reeds. I'm still trying to wrap my head around the fact that what appears to be a small issue with the reeds can cause the engine to run so horribly.


EDIT to add:

I disassembled a couple of the reed blocks and it looks like a previous owner (probably the moron I bought the engine from) did exactly what we talked about - flipped the reeds. Every one was bowed up in the middle, and when I flipped them (presumably back to their original position) they all had a gentle curve and the end of each reed was between 1/32 and 1/16 off the reed block. ALSO, the #6 block had a couple of small (maybe 1/16 by 1/16) gouges in the area where the reeds seat.




Modified by groundloop at 5:38 PM 5/13/2011