96 Mariner 115 stalls going into gear

[pinellas50]

1996 Mariner 115 hp 2+2 motor.

We were able to take the boat out yesterday after the wait through Winter. It started and ran great. The only issue was it started with this stalling routine when trying to put it into gear from idle. This was most fun while trying to maneuver into and out of docking at a busy restaurant with lots of expensive boats around.

Anyway, 2 winters ago I went through the carbs and had my mechanic do a link and sync on it. Over this Winter I replaced everything in the accelerator circuit of the motor. Yesterday was the first sea trial after that repair and it ran just like it used to. The idle seemed to be around 800 in water and 1000 on the muffs in the driveway.

Am I looking at a simple adjustment to get on top of this stalling thing? Mabey an adjustment in idle mixture?

 

[James R]

Re: 96 Mariner 115 stalls going into gear

You may have one cylinder not firing well at idle. Could be many things from plugs, plug wires, poor switch box, poor carb function
Quick check. Let it idle and pull the plug connectors off one at a time and see if one is not firing. Using a spark tester check for intermittent or weak spark at all the plug wires. Corrosion in the plug wire caps can be the culprit.

 

[pinellas50]

Re: 96 Mariner 115 stalls going into gear

Interesting. I was just about to get new wires because every now and then I think I am hearing a plug wire arcing. Every now and then I also get what feels like a cylinder dropping out for a split second, randomly, while cruising. I thought that would be a separate issue and possibly related to a plug wire. I was going to replace the plugs at the same time as the wires just for good measure.

Thanks for the tips James. I'll play around with these ideas and see what happens.

 

[pinellas50]

Re: 96 Mariner 115 stalls going into gear

Update: I went to my mechanic's shop to buy new wires which he was very against. He said he rarely sees an actual marine spark plug wire go bad. He said normally problems arise with cracked boots. I wasn't able to get the wires that day because I didn't know what type of coils were on the motor...apparently there are 2 types for this year. I went back once I knew the answer but the mechanic wasn't there so I talked to his assistant. His assistant had the same reaction when I said I wanted to get new wires. The assistant said mabey I just had the idle too low.

So I took it out this Tuesday for a day of fishing without doing anything to the motor. The motor idles at 1K normally....sometimes dropping down to around 800 rpm. It had the same symptoms of frequently stalling out when I put it in gear and I normally had to juice it to keep it from stalling. It also had what sounds like a high speed miss come and go while under way. The miss sound was there last year but not as frequent. The stalling is new this season. The only exception to all of this is last year, if I was pulling a tube for a long time, the motor would start doing this stalling thing. But it would clear up once we were done and we cruised a bit.....like the motor had been loading up with fuel but then cleared out at cruise?

What was new on Tuesday is if I tried to troll at 1K the motor would frequently shut off. In the past if it was in gear and the motor didn't like the low rpm it would start to chug for a bit before stalling. Tuesday it was running smooth at 1K and it would just quite. It would always refire immediately and did fine running for long periods of time at 1200 rpm.

So tonight I pulled the plugs and wires. All the wires looked fine with no signs of corrosion anywhere. The wires are a mis matched bunch as if the previous owner only replaced 2 of 4 at some point. The boots and everything else about the wires looked good. No corrosion on the tops of the coils or plugs.

I pulled the plugs and all but 1 look fine. The cylinder down one from the top had a plug that seemed to be much richer than the rest and it still had a fuel/oil residue on it which the others did not.

Am I most likely looking at a carb or ignition issue here? I will have to find the tool to check for a weak spark so I can't answer that question right now. I'm just looking for guidance towards the most likely culprit.

Sorry for the long post.

 

[oldman570]

Re: 96 Mariner 115 stalls going into gear

I would replace the plugs as iot sounds like the wet/fould plug was not fireing all the time. Run some Sea Foam with the gas to help clean up the fuel system an carbs and see if that makes any improvement in the low RPM running of the motor. A spark tester can usally be bought at most auto stores to test the spark, and is alot cheaper than throwing parts at it and not fixing the real trouble. JMO
Oldman570

 

[pinellas50]

Re: 96 Mariner 115 stalls going into gear

I have a copy of the Merc manual for the motor now and I see all the testing that can be done. It talks about using a Direct Voltage Adapter(DVA) meter to test certain things.

Do I really need to spend $100 for one of these meters or can common sense be substituted with a reasonable certainty of success? I am really having trouble justifying buying something at this price that I might only use once. Can one be found cheaper somewhere?

 

[oldman570]

Re: 96 Mariner 115 stalls going into gear

Here is a link as how to make a DVA adapter to do testing on your motor.
http://forums.iboats.com/mercury-ma...talls-going-into-gear-596614.html#post4164456
You will have to read the post and you can thank Laddies for the info .
Oldman570

 

[pinellas50]

Re: 96 Mariner 115 stalls going into gear

Your link comes back to this thread oldman. I'm anxious to see how you build one of these even though I hope I don't have to use it.

And I appreciate your help oldman. I have been here for a few years and have yet to figure out how to get the search function of this site to work to my advantage.

 

[pinellas50]

Re: 96 Mariner 115 stalls going into gear

Which 2 cylinders does this motor idle on? The top 2 or the bottom 2?

 

[oldman570]

Re: 96 Mariner 115 stalls going into gear

Let me see if the link will take you back to a thread by Sutior about a 1989 115 Merc that stalls when going to WOT.

http://forums.iboats.com/mercury-mariner-outboards/1989-mercury-115-acting-funny-idle-590590.html
This should be the place to find out how to make a DVA adapter as Laddies has posted .
Oldman570

 

[Faztbullet]

Re: 96 Mariner 115 stalls going into gear

Which 2 cylinders does this motor idle on?

Top 2... also a flooding carb can cause this.

 

[pinellas50]

Re: 96 Mariner 115 stalls going into gear

Thanks to the both of you! Common sense is leading me towards an ignition issue based upon that high speed miss. But I am used to cars so mabey my common sense is way off. I'll play around with it and see what I come up with. Thanks again!

 

[CharlieB]

Re: 96 Mariner 115 stalls going into gear

You might also check the coils grounding point, make sure connections are clean and tight.

 

[pinellas50]

Re: 96 Mariner 115 stalls going into gear

An update. What I didn't say about my April outing was on 2 occassions the tach stopped working for a short amount of time as if the rectifier died. But then the tach came back and worked fine the rest of the day. I don't know if that might be connected to what I have going on.

Since April I put in new plugs and new plug wires. I swapped the coils between cylinder number 1 and 2 to see if the evidence on the spark plugs of a poor cylinder moved. I took the boat out Saturday and it started easier than I ever remember. It ran well at first but then started back into the miss fires at low and high speed(they would come and go...ie intermittent) and the stalling when going into gear. We had the boat out for about an hour ride in total.

I pulled the plugs after I got back and the plug on cylinder number 2 is still showing that it is trying to foul. So I have narrowed this down to the switch box, trigger, or the carb. Everything in me says this is an ignition issue and I think I have had an ignition issue since I bought the boat. Here is another thread from my past which I now think are related if anyone cars to read all this:

http://forums.iboats.com/mercury-mariner-outboards/fluctuating-rpm-96-mariner-115-a-444313.html This post deals with fluctuating rpm under load which a full rebuild of the entire fuel system did not correct. That symptom went away for no apparent reason and has not resurfaced with my current issues.

Anyway, I am at the point of just going ahead and replacing parts. Yeah throwing parts at it is another way to say it. Is it safe to say the switchbox is the most likely culprit? That is what I am coming up with. I'm OK with replacing it and it isn't the problem.....I will then have a known good part for testing in the future. I'm just trying to see if others concur a switch box is more likely than a trigger with my symptoms.

 

[CharlieB]

Re: 96 Mariner 115 stalls going into gear

Throwing parts at it is the most expensive method of repair.

Troubleshooting will sort this out within 30 minutes.

Tools needed are a spark tester, remote starter button, or a friend, and a DVA meter or a DVA Adaptor for use with any Volt/Ohm meter

Disconnect the throttle cable so you can move the throttle by hand while testing the trigger output using the DVA. It is entirely possible that a trigger wire is broken but still have the ends touching part time and firing the cyl but when moved they come apart and the cyl doesn't fire any more.

Verify trigger output at all throttle positions, once you have proven the trigger good/bad you can move on to the switchbox output to the coils.

 

[pinellas50]

Re: 96 Mariner 115 stalls going into gear

Do you know of some sort of tutorial I can read/watch which will explain exactly how these tests are supposed to be done? I haven't seen anything yet that really explains what I am supposed to do to perform these tests.

 

[CharlieB]

Re: 96 Mariner 115 stalls going into gear

Read the section on the 4 cyl Merc ADI, you will see the tests spelled out

CDI Electronics Practical Outboard Ignition Troubleshooting

I haven't looked, but I bet youtube will pull up any # of stator tests or trigger tests, a # of people take the time to record and post

You can build a DVA adaptor very easy and very cheaply

Simple, easy to make DVA adapter for standard Multimeter?/ 374544

 

[pinellas50]

Re: 96 Mariner 115 stalls going into gear

It really doesn't spell out how to run a DVA or resistance test. Only the numbers you should see. But I do appreciate you trying to help me and make me do the right thing.

 

[CharlieB]

Re: 96 Mariner 115 stalls going into gear

The DVA adaptor connects to the two leads from your vol/ohm meter, two leads from the other side of the DVA adaptor then become your two leads to connect to the item being tested.

Meter must be set to DC Volts of a range high enough for the expected voltage.

The resister in the adaptor places a load on the item causing the voltage generated to do work, the capacitor stores the voltage long enough for the needle to 'hover' so as to get an accurate reading. Without the resistor there would be no load, no real current flow,, a broken winding with the ends abutted will generate a voltage but the moment any load is placed on the circuit the voltage will drop to zero, LOAD is key to getting a reading. Without a cap to stabilize the voltage, the needle would swing up then immediately back to zero, no time for a meaningful reading.

 

[pinellas50]

Re: 96 Mariner 115 stalls going into gear

I found instructions in a Seloc book I have which somewhat made sense so I started following those directions starting with checking the resistance on the trigger and stator. On the trigger it said I should be between something like 700 and 1200. My meter said something like .85 which I am assuming is 850. The resistance on the stator was lower that spec on the red to red/white. The blue to blue/white was supposed to be something very high and my meter didn't have anything close. I had unbolted all leads from the switch box to do these resistance tests, wrote everything down as I took them off, then put them back on the exact same way. Verified against a wiring diagram.

I was going to try and figure out the DVA tests, testing with the motor running. But now I have no spark on any hole. The exception is when I let off the key it looks like I might get one spark on occasion which leads to what sounds like a back fire when it happens. So the DVA tests didn't happen.

I noticed a redish brown powder like substance on the engine block underneath the flywheel. I don't know if that is pertinent.

So now I am at more of a loss than before. The troubleshooting guide has the switch box as suspect with a complete no spark and intermittent spark on only one cylinder like before.

I don't know what I could have damaged with a simple resistance test.