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Challenge: Who can solve this?

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danalex1

New member
I have a 1986 mercury 2 stroke 60 hp outboard. It set up for some years. It would run and idle, but bottom cylinder was not working. Compression is 100 lb on all three cylinders with a harbor freight gauge.

I cleaned the carbs and replaced the main jets. I rebuilt the fuel pump. Gas is clean, filter is clean. Got all cylinders running.

The motor runs at 2700 to 3000 rpm. Throttle cable is disconnected. Butterflies are closed in the carbs. There is .020 clearance between the carb throttle roller and the throttle advance when the throttle arm is at the lowest position. I have adjusted the spark advance to retard spark as far as it will go. When I manually retard the spark by moving the lever by hand it does not slow down.

I sprayed carb cleaner around the carbs and fuel pump while the motor was running looking for where it was sucking air and found a little, pulled them all off and sealed with permatex. Now there is no change when I spray around the gaskets with the motor running. I took the new needle valve and seat out of the lower carb and put the old one back in. No change. There is a steady stream of fuel coming out of the first small pipe in the lower carb. I put my finger over it and the motor slowed a little, coughed. The motor is running smoothly. THere is a hesitation when I advance the throttle quickly to max (WOT) the first time, the second time there is no hesitation, the motor revs quickly. I do not do this a lot, I think it is bad for the motor. I got to replace the impeller again before I can restart it, but if anyone has any suggestions I will do them immediately if there is any chance of it working.

I do not have a manual, I do have information off the internet about link and sync and have followed that except where it requires a timing light. I do not have a timing light. I will get one if I have to.
 
The throttle slide on those is made to slightly open the carbs at part throttle, to reduce bogging. At idle speed, the carbs MUST be fully closed, and if you carbs are not, the slide is not far enough to the right side (of the motor). Readjust the linkage until the carbs are closed at idle.

Bogging on triples is cured by opening the idle mixture screws another 1/4 to 1/2 turn OUT (CCW) after you obtain best idle. I use an infrared temperature gun aimed at the metal of the plugs to get them all the same temperature, then add the 1/4 to 1/2 turn out.

Jeff

PS: THese are notoriously difficult to tune and poor idling motors to begin with, so hang in there.
 
My main concern is getting that high idle down to the point I can put it into the water, put it in gear, and do the final tuneup. I will go get a timing light and check the reading on each plug. Another piece of info: I suspected the flywheel might have shifted, causing advanced timing, so this morning I found approximate top dead center in the number one plug with a screwdriver. I then looked at the metal arrow timing marker next to the flywheel, it is pointing to the 464 mark on the flywheel. I think this means the flywheel has not shifted.
 
Motor still runs fast with idle as slow as it will go. Apparently, air leaks will cause the engine to run fast. So far I found leaks around the fuel enrichment valves on both carbs, replaced them (12 bucks a pop, not bad at all!). I get about 3000 rpm on the lake with that. I suspect wear around the throttle shaft is leaking air now. I rebuild the fuel pump, it was leaking, fixed that. The seal to the block does not appear to leak. I covered all the welch plugs with permatex - it might not last, but should have sealed leaks and from what testing I can do they are not leaking air. (I tested by spraying carb cleaner or now, seafoam, with the engine running. If the sound changes, there must be a leak. The enrichment valves almost killed the engine when I hit them with the spray). On the lake, running at 3000 rpm in gear, I was able to take the idle screw out of the bottom carb without changing the rpm. If I adjust it to about 1/8 to 1/4 turn open from all the way in, it runs a little better. I will pull the plugs in the morning and see what they say.
 
fastjeff said:
The throttle slide on those is made to slightly open the carbs at part throttle, to reduce bogging. At idle speed, the carbs MUST be fully closed, and if you carbs are not, the slide is not far enough to the right side (of the motor). Readjust the linkage until the carbs are closed at idle.

Bogging on triples is cured by opening the idle mixture screws another 1/4 to 1/2 turn OUT (CCW) after you obtain best idle. I use an infrared temperature gun aimed at the metal of the plugs to get them all the same temperature, then add the 1/4 to 1/2 turn out.

Jeff

PS: THese are notoriously difficult to tune and poor idling motors to begin with, so hang in there.
Click to expand...

Does that actually work? That sounds like a great idea. I have a 2005 60hp ELPTO on premix and I always have had a hell of a time getting the idle right on mine!

So you can actually tune the carbs to spark plug temp? What temps are you shooting for and what are the differences if any? I'm going to try this today. I'm always a little paranoid about running too lean.
 
I think you misread, not temp, tach -meaning timing. I am tied up and don't have the timing light yet. I do have a 1/4 gap between the carb throttle roller and the cam. The butterflies are closed. Actually, the carbs are off right now, I am replacing the bottom one, throttle shaft is so worn it wobbles and lets air in.
 
danalex said:
I think you misread, not temp, tach -meaning timing. I am tied up and don't have the timing light yet. I do have a 1/4 gap between the carb throttle roller and the cam. The butterflies are closed. Actually, the carbs are off right now, I am replacing the bottom one, throttle shaft is so worn it wobbles and lets air in.
Click to expand...

Negative.... Did you even read the second paragraph in post #2? He clearly states that he uses an infrared thermometer to check spark plug temps.
 
danalex said:
You are exactly correct, I missed that. Thank you for pointing it out. It sounds strange.
Click to expand...

It sounds interesting! Especially if it works. I have had idle issues with mine since I have owned it. I know that these engines are not exactly smooth at idle, but just a little smoother would be nice. On mine, the idle is not too rough, but I feel like it could be a tad smoother... Anything off idle is pretty much electric smooth.

Did you ever get your issue sorted out? Or are you still working on it?
 
Still working on it. While I had the carbs off I jury rigged a seal on the carbs and blew smoke into them. The lower carb was leaking around the float bowl freely. I fixed that and rechecked, there is a hole on top of the carb that leaks; I do not know if it is supposed to, it is the same on both carbs and is a factory hole. I put the carbs back on and got the motor cranked - had to work with it a little, settings changed quite a bit on idle screws and I found the top enrichment valve is sticking open. Motor still idles high, about 1500 rpm, but now not leaking fuel. While doing the link and sync I found I did not tighten the link between the top and bottom carb throttle shaft, and I cannot get to it without pulling the carbs back off. That prevents the throttle butterflies from opening to 90 degrees at WOT. Should not impact idle. With spark advance set to minimum physically possible it runs at 1500 rpm. Next step I can see is to seal carbs and pressurize them, with smoke if possible, and see if I have a seal leaking. I am not sure if that will work with the ports in the cylinders, but if I can get smoke in there it might. Any advice or suggestions welcome - I have located some new carbs, but I don't know if they would make a difference. I could be leaking around the flanges I guess....I really worked at making sure there was no leak there but I would like to check anyway. That would be much better than having to change the seals.
 
I closed the top enrichment valve, re read and discovered I left that hanging, yes that would cause and did cause problems.
 
Ok, smoke test results. Not leaking around the mounting flanges. Got back pressure on each carb at idle throttle, carbs do not appear to be leaking one into the other at idle setting on the throttle. When I advance the throttle to WOT I get smoke out of the other carb. I do not quite understand that for sure. butterflies are making some difference but there are small holes in the butterflies. Still get smoke from orifice in the top of the top carb. Did not see any smoke from the hole in the top of the bottom carb. Running smooth at 1500 rpm when I started it after the carb test. I checked and made sure the spark advance was as far in the clockwise direction as it could physically go, it hits the stator housing and will go no farther. This should be the most before top dead center, or the most retarded, the spark can be. Next step: I can buy 2 carbs. I can try to rig the spark advance so I can retard it more. I can pull the flywheel and see if there is any way to set timing, but I am pretty sure the flywheel is keyed in one way or another so it cannot be rotated in relation to the trigger and stator to set timing. Top dead center #1 cylinder is exactly, to the best of my ability to detect, at .464 on the flywheel. Which is recommended in the link and sync. I am at a loss.
 
I've ordered the tool to pull the flywheel with. I could get it through a local boat shop but it was $500 dollars. It is 11.89 off amazon or ebay (other prices too). I will see if the key is letting the flywheel rotate away from where it should be.
 
Flywheel is off. I didn't realize til after I had it off I shouldn't remove the bolts holding the flywheel to the part that sits on the shaft splines. There is no key, there is a difference in the spline pattern at one point that forces the flywheel to align. It looks ok. No broken, no sheered. So. The trigger will not physically move any further to retard the spark. I am going to assume it is ok where it is, and not use a dremel to give it more movement. So either the control box is advancing the spark a few degrees consistently or the engine is still getting excess air. I will get replacement carbs. I will go out and pressure check the engine with the flywheel off. I will try to replace the flywheel where it was when I took it off. I took the little bolts out that held the flywheel to the part that splines onto the shaft. I am going to try to figure out exactly where it should fit. I will also break down and buy a dang timing light I guess, see if there is a problem with the fire.
 
These motors are notorious for burning up their top cylinders. Get a compression check before you go any further. AutoZone will lend you one.

Jeff

PS: I too have had problems with the trigger coils on these not moving enough--in advance one time, and retard the other. Crappy quality control.
 
Hey fastjeff, I burned up a cylinder in a merc 40 I had, it can happen easy. I bought a compression gauge set from harbor freight when I was looking for a motor, I've tested compression and get 100, 100, 100. Low compression but very little variance. As much time and work as I've put into this, I am very tempted to go ahead and order rings.
 
I read some information on reed valves. Apparently if a reed valve is not closing, broken or missing pieces, I should get some blowback through the carb(s). I don't have any blowback. Also should make it idle rough and hard to start, and should have trouble getting fuel into the cylinders. My cylinders are running wet, on purpose, I am wary of a dry cylinder since it will burn up quick. This motor cranks up pretty good. You have to choke it when it's cold but it fires right up and runs pretty smooth for a merc. It just idles fast. All plugs are black and damp. I am running a little heavy on oil in the gas, so expected. If I lean the carbs out with the idle adjust it runs faster and plugs are cleaner. I did have problems getting WOT in the water in gear, running; chokes and sputters when I advance the throttle. Max 3000 rpm while tinkering. I checked for blowback while doing this by blocking the carb intake with my hand and I feel suction. Get a little fuel on my hand if I choke it down thouroughly but I think that is to be expected. Motor reacts badly to blocked air and chokes down on either carb.
I sealed the carbs while they were installed on the motor and rigged an icemaker line through the seal. I blew smoke through the icemaker line into the carbs one at a time. With the throttle at idle and butterflies closed, I get backpressure and no smoke anywhere other than a vent hole on the top of the carb. Both carbs same. With the throttle at WOT I get smoke out the other carb. Not a lot, kinda slow, but they are connected. What does that mean?
 
I got a pair of new carbs and installed them today. I had to adjust the idle mix and do a link and sync. Motor idles at 2000 rpm. Top plug black and wet, almost gummy. Middle plug has deposits on it, kinda gray and crusty. Bottom plug wet, shiny, a little black. Spark will not move any further clockwise, which should retard it. the wiring harness hits a stator bolt and stops the trigger from moving any further. At max throttle, the trigger has another inch it could move in the counterclockwise direction, advancing the spark. There is no way I can find to get the trigger slower. Could reed valves cause the high rpm at idle? could it be a bad trigger or switchbox in some way?
 
I just took the timing light and checked timing. Set top dead center on #1 on the pointer - it was dead on, I just checked it. Timing light shows pickup timing is at 13 degrees btdc. Manual says should be 7 - 9 degrees. Trigger is against the bolt housings for the stator, they do not move. Trigger has no travel left to retard timing another 4 or 5 degrees to get to 8 degrees ( 7- 9). The only way I can see to get that extra travel is to remove some of the stator bolt housing. I would really appreciate someone's input before I do that, I feel I may be missing something here. I don't know how the motor ran with this condition and I cannot see what changed. Help?
 
Thanks pin - I found a wire corroded in two where it comes out of the trigger plastic housing and ordered a replacement trigger. Maybe that was causing the problems. If not, the stator is easy to move, and I can tell where it was by the bolt holes that were used. Easy to rotate. Should not be the problem from what I understand - stator charges the capacitor, trigger tells switchbox to fire the coil, but I am willing to check it out if trigger doesn't fix it.
 
I replaced the trigger and there was no real difference. I checked the timing, marked 1, 2 and 3 top dead center on top the flywheel and checked with the timing light and it did not add up. I went to the manual, the first schematic I came to showed the wiring correct. Just for the fun of it, I checked the exact engine I have, and the @2 and #3 coils were swapped. I corrected that, the motor started, idling at 600 to 800 rpm now. It is fixed. Problem solved. I might check the timing for the link and sync, what I did was work with the carbs and throttle and spark timing while it was running to get best idle, then slow it down. It is running warmer than it has been because it is running on all cylinders. Response to throttle is instantaneous after enriching the idle adjust a little. Thanks for all the input to everyone!
 
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