1987 Classic 50 Misfire

[Navy ESWS Chief]

I'm sure this has been beat to death here, please forgive me!

My Classic 50 appears to be running on 2 cylinders. Very little power on the water. When doing the drop cylinder test on 1&2, RPMs do not change. Timing light visibly drops out when connected to #1 at lower speeds. Appears fine at higher RPM. Strangely though, the light appears to be on almost continually while other cylinders are still "strobing" for lack of a better word. Stator, Trigger Ohm out OK and DVA OK as well according to CDI specs. Coils Ohm out fine, spark appears good as well. Plugs are wet and oily. Also, the water in my cooling bucket (is there a word for that tank you stick the prop into?) is quite oily. Wonder if my gas is mixed wrong...help!

 

[Navy ESWS Chief]

Small update. I swapped positions of the trigger coil and the ignition coils at the power pack. The problem moved to the bottom cylinders. That exonerates switch box, right? I suspect it must be the trigger coil that is bad. Even though it ohms out OK. That is puzzling...it's just a coil of wire. I haven't pulled the flywheel. Could the magnet be at fault?

 

[Navy ESWS Chief]

OK, looks like I'm here alone, but I'll keep going for the lurkers! Ordered a trigger unit and a flywheel puller. Let's see what happens!

 

[Kelvin1]

Try this helped me

 

[Navy ESWS Chief]

Thanks Kelvin1. Yes, I have that memorized. All my DVA readings and Ohm readings are OK. I have a trigger on order because of the problem I mentioned above. Should arrive tomorrow. We'll see!

 

[Navy ESWS Chief]

Replaced trigger. It really doesn't run any better, except it appears that the #1 cylinder misfire indicated by the timing light has been fixed. I now suspect too rich a mixture. Closing the idle screw all the way down has no effect on engine. Top plugs are oily and clean, like no combustion. Next step - set float level. Already replace needle and did a vacuum/pressure holding test, which looked reasonable, though there's not much out there about it. Also, new gas (not that other was very old, but I think waaay too much oil judging by the smoke cloud the neighbor hood is clouded in when I run it!

 

[racerone]

When idling the motor should slow down / stall when you turn slow speed needle all the way in.----Revisit carburetor work.----Post the compression test numbers too.

 

[Navy ESWS Chief]

Thanks racerone
Compression was 120 PSI +/- 5 on all cylinders, thank goodness. I'm going after the carbs, for the 3rd time. I suspect float level. Last time I worked on these, I couldn't find any decent info on the float level. Should they be "level" with the carb body? (when upside down?) Or is there some distance / spacing I need to ensure?

Could this be an exhaust blockage? Or reeds? The donor motor I've been "practicing" on had the exhaust tube about 75% blocked and chunks of carbon in the power head.

 

[racerone]

The reeds are quite reliable.----They are way inside the engine around the crankshaft.------But critters / mouse nest / seagull feathers could get in and hold them open.-----Who knows what happens to motors these days.-----Simple trouble shooting finds the problems.

 

[Navy ESWS Chief]

racerone Good to know. I'm lucky enough to have use of an inspection camera. I'll poke it in there when I have the carbs off. I'm sure an inspection mirror would work as well. Should I buy the service manual? I mean, for 90 bucks, I might be able to fix the motor! I guess it ups the re-sale!?

 

[Navy ESWS Chief]

I adjusted the float levels and this made no difference whatsoever. Won't seem to idle. The engine runs (poorly) even with the idle jet screws turned all the way in. The timing just to run is somewhere between 9 and 32 (where there are no markings) It won't stay running if I hold the timing at about 2 degrees.

Summary: Replaced: Trigger, #1 Coil, float needles, plugs. Cleaned Carbs. Rebuilt fuel pump (was missing engine side gasket). Fresh ethanol free gas mixed 50:1 exactly!. Swapped switch box with used switch box - no change. Drop cylinder test no change with #1 & #2. Good (?) spark. Plugs oily. (all)

New unrelated problems seem to be leaking lower unit shaft seals, which explains the oil slick in my cooling water tank. Yay.

Time for a pro?!

 

[217andy]

My experience with using a timing light to troubleshoot spark is that it is very unreliable. I have better luck in a situation like yours to pull off one spark plug wire at a time (with the engine running) to see if it makes a difference. It is a sure way to find out which cylinders they are running on. If, for example you pull the top two wires off and it makes no difference, try giving it a shot of carb cleaner in the top carburetor to see if it perks up (after reinstalling the spark plug wires of course) If you don't have a plastic wire puller, you can use any metal pliers as long as you connect a wire from the pliers to engine ground, it will keep you from getting bitten.
If you have good spark you will be able to hear it snapping when you pull the wire off.

On the carbs, one important note is that the throttle plates in the carburetors MUST be completely closed in the idle position, otherwise it cannot run on the idle circuit. Make sure your throttle plates are synchronised to both open at the exact same time. Good luck

 

[Navy ESWS Chief]

217andy Thanks for the tips. I did the drop cylinder test and it is clearly the top two cylinders. Spark is present on all cylinders. Right now I'm leaning toward a weak stator or possibly misaligned stator, but there seems to be controversy on whether it matters if your stator is lined up. I don't understand why the timing has to be so advanced for it to even run. That's got to be a clue and the only culprit would seem to be stator problems or alignment. Ugh.

 

[The Force power]

I adjusted the float levels and this made no difference whatsoever. Won't seem to idle. The engine runs (poorly) even with the idle jet screws turned all the way in. The timing just to run is somewhere between 9 and 32 (where there are no markings) It won't stay running if I hold the timing at about 2 degrees.

Summary: Replaced: Trigger, #1 Coil, float needles, plugs. Cleaned Carbs. Rebuilt fuel pump (was missing engine side gasket). Fresh ethanol free gas mixed 50:1 exactly!. Swapped switch box with used switch box - no change. Drop cylinder test no change with #1 & #2. Good (?) spark. Plugs oily. (all)

New unrelated problems seem to be leaking lower unit shaft seals, which explains the oil slick in my cooling water tank. Yay.

Time for a pro?!

As Racerone already said; it will stall when air/fuel-mixture screw is screwed in!
unscrew this about 1 turn & 1/2 out

The oil slick in the cooling tank is just the unburned oil/fuel mixture coming out of the exhaust, even when it does run proper; the re-circulation system does not kick-in until the motor runs at higher RPM's (3000+)

Get a sparkplug tester and check the gap it can jump (min.3/8")

Inspect the Stator wires they tend to break inside the insulation, pull the ends firmly to see if the insulation stretch or not? Check the ground wires if clean & tied

Keep us posted

 

[Navy ESWS Chief]

Even though it makes little sense to me, and I'm on my last bit of enthusiasm for this beast, I rotated the stator one bolt hole clockwise as viewed from the top. This did place the wires in a slightly better position than before. They appeared to be rubbing against the throttle actuator arm. No wear detected, though. The motor actually ran better than ever. I was able to actually run the motor with 2 degrees ATDC timing and adjust the idle. Now, seems that all cylinders are firing. Still runs kind of rough, however.

There seemed to be very little on how to install the stator. Other than "install exactly the same way it came out". Well, that's great if you're the first guy! Others said "wires come out on starboard side next to "split case"". I don't get that. I do know starboard is the right side, however!

Maybe I do have a bad stator and just fiddling with it "fixed" it. The rubber boots on the terminal ends are deteriorating, so I'm guessing it is quite old. It's a CDI replacement. Who knows when.

Comments or philosophy on stator indexing? As an EE, I can only reason that the pulse from the hi/low speed coils is phase shifted maybe 15 degrees. Why that matters is a mystery. Not knowing how the switch box handles this doesn't help, and apart from reverse engineering the switch box(pr finding a schematic!), it's all speculation.

If I can get it back together before the sun goes down, maybe I'll get it on the water tomorrow!

 

[Navy ESWS Chief]

So, I got it out on the water today. Imagine my family's reaction when it wouldn't start. Kind of hard to work on bobbong up and down leaning over the transom, so I didn't get far. Good spark as far as I can tell. Good gas. What the heck!? It ran in my driveway! Going to Mercury Mechanic tomorrow! I give up!

 

[racerone]

Very good decision I say.

 

[Navy ESWS Chief]

It was a loose plug. Still runs like crap. Still going to mechanic. I'll post the post mortem report here!

 

[Navy ESWS Chief]

Sadly, the mechanic, a very nice guy, but perhaps overloaded, did not fix my problem. It appeared to actually run well on the trailer when I picked it up. Full throttle revealed what sounded like a slight miss, which he admitted to. In any event, the switch box was bad and I had screwed up the timing. He did not take it on the lake. If he had, as I did with my family the next week, he would have discovered that top speed was about 10 Mph, and we are not that fat. (but winter is not over yet!). So, back through the carbs and some other maintenance this winter. (at least the trailer doesn't have an engine!) I did knock a giant carbon plug out of the exhaust that blocked probably 75% of the tube (while replacing water pump). Perhaps that will unleash the lost horses. I plan to rebuild the carbs again, this time with all new jets, etc, instead of just needles. FWIW, the seats did seem to leak, but I was able to polish them out and they do hold a few PSI of air indefinately, now. Will try with gas when I get them off next time.