87 Mariner 60 hp running on 1 cylinder

[Tylerevenhuis]

Hello all. I just bought a pontoon with a 1987 60 hp Mariner outboard on it and it's not running well. Basically it's only running on the #1 (top) cylinder, misfiring on the #2 (middle) cylinder, and not firing at all on the #3 (bottom) cylinder. This motor is a three cylinder two carb motor, so I pulled the carbs and completely cleaned the bottom carb. It was quite clean to start with. But this didn't change how it runs at all. I checked spark and all the plugs are sparking well when held against the block. Wondering if anyone has any ideas to try next. I feel like this is ignition related because while it was running I adjusted the idle jet on the bottom carb and that didn't change how it was running at all either. Any help you have would be appreciated, thanks!

 

[Tylerevenhuis]

I should also note it has good compression on all 3 cylinders, between 145 and 150 on all 3.

 

[danalex]

If you have good spark and compression the the problem is fuel and/or timing. Top cylinder runs so maybe timing is ok. Are you getting fuel to the bottom plugs? The top carb feeds the top cyl and partially the bottom, based on my experience. Either the bottom carb is not letting fuel feed through or something else is preventing it. If you pull the drain plug out of the bottom carb, does fuel run out of it? If not, pretty sure you have a sticky needle valve/float problem.

 

[jimmbo]

Well the 2 carb into 3 cylinder is usually a real pain, but in your case it is yeilding an important clue, both carbs feed the 2nd cylinder. #1 is fine, #2 is so-so(misfiring), and #3 is dead. That means #2 is getting some gas and air from the top carb but only air from the bottom carb and is lean, and #3 is also starved. Pull bottom carb and give it a thorough cleaning, and float adjustment.
Fuel line to bottom carb might be blocked/kinked/internal deterioration, prevent fuel from getting to carb

 

[Tylerevenhuis]

Thanks for the replies! I think I found the problem. I was messing around with it and after pulling the carbs off cleaning them and not having any luck I thought I would pull the idle jet out and spray carb clean in that port to make sure it was open. I sprayed it in there and saw it coming into the throat of the carb like it was supposed to, then I noticed it dripping from the bottom of the throttle shaft that the butterfly connects to. So I think the seal on the bottom of the carb is bad and is in turn causing a massive vacuum leak. I ordered a new seal that should be here next week so I will let you know if that solves the problem. Thanks again for your help guys!

 

[Tylerevenhuis]

No dice.... I replaced that bottom seal and completely cleaned the the bottom carb again and replaced fuel lines and filter. Still have the same problem. I'm wondering if there is something in the ignition that is throwing timing out? Like it's ok on #1 a little off on #2 and way off on #3. Is that even possible? Is there a way I can test those components? I'm to the point I will have very little hair left in a short amount of time. Thanks again for your help fellas.

 

[danalex]

Is the bottom cylinder getting fuel? Pull the plug and look at it. Maybe the spark could be messed up on one cylinder like you said, but I that is a long shot. I am dealing with a 3 cylinder 60 hp merc myself, and getting fuel to the bottom cylinder was a massive pain. Pulling the plug is easy. If it is dry, then you need to check
the Float in the bottom carb to make sure it is opening. Can turn carb upside down and blow into fuel hose, should be closed, then turn right side up and blow, should open. Float can catch on gasket or bowl in this model motor! (wm-13, 18 carb)
Is the bowl leaking? that will let fuel drip off the throttle spring on the bottom of the carb, and will cut down on fuel to the bottom cylinder
If you have one of the same carbs I have, they come from the factory with a screen at the bottom fitting. Make sure fuel can get into the bowl. The manual recommends not replacing that screen during a rebuild, may get plugged up.
The trigger is round, inside the flywheel. The flywheel has magnets on it. When a magnet passes a trigger coil it generates electricity that feeds to the switchbox. Timing is set based on the relationship of the trigger to the spinning flywheel, is difficult for just part of the timing to be off. Your problem sounds like the same sort of thing I have been dealing with and so far it has all be fuel and air. I cleaned my bottom carb 5 times and replaced the jets and seats to get the bottom carb flowing well. I still have problems and I am replacing both carbs.

 

[Tylerevenhuis]

Hey Dana thanks for getting back to me so quick. I checked the plugs. The tops one was a bit wet but looked like it was firing. (It takes a lot of cranking and messing around to even get it to start) the middle plug was black and sooty and fairly dry. The bottom one was wet and clean. Didn't look like it was firing. The last time I cleaned the carb the only thing I didn't take apart was the fuel inlet fitting. I tried to take it out but it seemed stuck and I didn't want to break it. Do you know how that comes out? Is it threaded in there? Also I think that bottom seal is supposed to leak. It's sort of a cupped shape so I think when there is vacuum on the carb it pulls the seal tight, but if there is any volume of liquid in the throat of the carb it leaks out as to not hydro lock the motor. Have you been able to find a replacement carb for that motor? In my limited searching all I could find were a couple used ones on eBay. The other thing I noticed was on my stator there are 2 wires that were cut off. Like maybe that stator was for a v6 or something. I have no idea what the guys who had the motor before me did to it. When I picked it up most of the ignition components were loose or had been taken off.
I did resistance tests on the stator and trigger according to my repair manual and the trigger passed those tests. But for the stator one of the tests was border line. The range was 4. something k ohms to 6.2 k ohms and mine tested at 6.25 k ohms. I'm not sure if that means it's bad or that it's just way at the top of the range and is still ok. I also question if a bad stator could cause the problems I'm having. Sorry for the long winded post and thanks again for the help!

 

[danalex]

After runng my bottom cylinder had a brand new looking plug that was wet, the top and middle exactly like yours. I took the wire off the top coil which, if I remember right, feeds the bottom cylinder, and swapped it to the middle coil which goes to the top cyl. I did not swap the ground, just the hot wire that fires the coil. I put the plug wires on the right cylinders for the way they were wired and started it back up. There was no change in the plugs or the way it was ran, which told me it was not the fire. After that, I found a speck in the lower carb idle adjust (Had cleaned the carb at least twice). I cleaned the carbs again and replaced the jets and the seats, cleaned the hold the seat came out of with a que-tip on a cordless drill, and cleaned anything else I could find or take apart. I recognize that throttle shaft seal, I had the same experience with it. After the last clean the bottom cylinder fired off and ran. Now the motor idles at 1500 rpm and is running on all cylinders. I cannot get it to idle down....

 

[Tylerevenhuis]

Well I'm a little embarrassed to admit it but I found my problem. I had the wires from the switch box to the coils in the wrong order. When I put it together (it was all apart when I got it) I assumed the wires went strait across to the coils, top to top middle to middle bottom to bottom. That's not the way they are supposed to go. Top goes to middle coil middle goes to top coil bottom goes to bottom coil. I found a wiring diagram online and hooked it up the way it should be and it runs like a champ. Dana your high idle has me some what baffled. I'm pretty new to this but if you want to bounce ideas off of me I'd be happy to try to help. Again guys thanks for all your help!

 

[danalex]

If you come back and look, I am just happy you got fixed and running. Enjoy. I'm waiting on the mail to deliver my carbs.

 

[Tylerevenhuis]

Hey Dana you mentioned you replaced the jets in your carbs, I was wondering if you got the right size. I think on those there isn't a high speed adjustment, you just change jet size depending on sea level elevation. so maybe if you got the wrong size you are getting fuel from the high speed jet while you are trying to idle. Maybe that is giving you your high idle issue. Not sure if that's even possible just thinking out loud.

 

[danalex]

I put the old jets back in at one point, this is from my memory so might be wrong, I believe they are supposed to be .092. I checked jet size based on the parts list and it is the same. Might be .072. I have it written down on my desk somewhere, I followed the same train of thought. Thanks for thinking about me!