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  1. #1
    Join Date
    Oct 2010
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    Charlotte, NC, USA
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    Default 1987 Mariner 115 hp In Line 6

    Been having problems with WOT, it will run about 15 minutes or so and then starts cutting in and out. I first thought starving for fuel but have eliminated all possible fuel problems. It starts up easy and will idle all day long if you want. I feel now it has to be ignition. I checked the ohm readings on the stator, trigger and switchboxes and they all check good, but since the problem is intermitant I guess they would check good.

    What would be the first item to replace or check? I'm thinking the switchboxes since they control three cylinders each. This would make sense when it boggs down as if losing half the cylinders and then they come back on line.

    Any help would be appriciated.

  2. #2
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    May 2007
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    Default Re: 1987 Mariner 115 In Line 6

    Did you check the stator warm? Sometimes there may be a crack in the windings which while cold will give a good reading but when it heats up it opens the crack and continuity is lost switchboxes are the last on my test list,the expense frightens the hell out of my wallet

  3. #3
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    Default Re: 1987 Mariner 115 In Line 6

    Have not checked it warm, but will do that today. Stator is about $160.00, switchbox is $130.00, but I see your point there are two of the switchboxes. I've been told to always replace both together if one is bad, is that true?

  4. #4
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    Oct 2010
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    Default Re: 1987 Mariner 115 In Line 6

    Thanks Haventaclue, I checked the stator leads with the engine cold and it checked 5.6 Ohms between one set (blue and red) and 5.7 between the other set. After warming the engine one set of leads checked 4.0 the other set stayed at 5.7. Mariner manuals says between 5.4 - 6.2 is okay. Will a difference of 1.4 cause this problem? Sounds like a bad stator, it does not show it signs of cracks, but I know this doesn't mean it's good.

  5. #5
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    Default Re: 1987 Mariner 115 In Line 6

    Stator is defiantly on the way out and yes it would cause this problem.You may not see the break if it is micro fine but the warmer it gets the wider the crack gets.Graham on this site has a wee test and it works,heat the stator with a hairdryer,it mimics the effect of the motor running and see if the #'s drop any further. And it is recommended to change both switchboxes if one is bad.

  6. #6
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    Oct 2010
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    Charlotte, NC, USA
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    Default Re: 1987 Mariner 115 In Line 6

    Just for curiousity, I heated the stator up a bit warmer with your hair dryer method. One set of leads stayed the same 5.7, but the other set was all over the place. Actually went up to 16.2, a few minutes later 15.0 and dropped more as it cooled off. I wouldn't have thought of the ohms climbing. Thanks for the help, and great response time. I've already order a new stator.

    Dave

  7. #7
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    Default Re: 1987 Mariner 115 In Line 6

    The stator needs a certain amount of resistance to work,hence you should get a reading of between 5.4-6.2. Less than 5.4 is too little,allowing the current to travel to fast for the stator to function properly,over 6.2 = too much resistance and the currant can't get there fast enough to operate properly
    " In circuits like plug wires where a set range of resistance is necessary for them to work properly, any reading other than the proper range indicates bad wires that need to be replaced."
    This explains it better than I can

  8. #8
    Join Date
    Oct 2010
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    Charlotte, NC, USA
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    Default Re: 1987 Mariner 115hp In Line 6

    Thanks Havenaclue, I do understand electrical resistance, I'm an electrician by trade, just was surprised at the resistance climbing rather than falling. I have the new stator but was thinking since the trigger is right there with it and a bit of work to get to, would you replace the tigger while the flywheel is off? It's only another $140.00? Or just let it ride since it checks good right now.

  9. #9
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    Default Re: 1987 Mariner 115hp In Line 6

    There was me trying to teach granny to suck eggs.Me been a bit of a skinflint I would put it back.Or put in the new one and put the old one on ebay to offset the cost of the new

  10. #10
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    Oct 2010
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    Default Re: 1987 Mariner 115hp In Line 6

    Teaching granny to suck eggs, haven't heard that one in a while. Been informative and a pleasure chatting with you. If I can help you with electrical work anytime, just let me know, I'm on year 28 as a commericial electrician. And by the way, the new stator took care of the problem , she's running like a dream. (I got cheap too and left the old trigger on.)

    Dave

  11. #11
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    Thumbs up Re: 1987 Mariner 115hp In Line 6

    Glad to hear it, happy boating

  12. #12
    Join Date
    Oct 2010
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    Charlotte, NC, USA
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    Default Re: 1987 Mariner 115hp In Line 6

    Well Haventaclue, thought the problem was solved but after about a 45 minute ride to the dam, it started cutting up again just as before. Replacing the stator wasn't in vain, because the alternator is working now and it hasn't charged in several years. I suspect the switchboxes but a marine mechanic here in town says it sounds more like a trigger to him. He said he's had lots more bad triggers over the years than switchboxes. The trigger tests within spec, but it he says doesn't matter since it's cutting in and out. What's your take, your advice has been sound so far.

    Thanks,
    Dave

  13. #13
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    Default Re: 1987 Mariner 115hp In Line 6

    Ok,retest the stator,unlikely but that's where I would start.On the off chance the stator is gone again,I would hope not,the question is,if it is gone, what's taking it out.Did you check out or replace the rectifier?I hadn't figured on the stator been out so long.Charge into the rectifier needs to go somewhere and if it's blown eventually the stator will burn. Then my next thought would have been the trigger,can you borrow one to try?.If it's checking out OK,test the coils and if they check out, then it's on to the switchboxes.
    This is where patience comes in,a buddy and a crate of beer required. An induction timing light is also required,go for a run and when the problem appears hook on the timing light to each plug to see which one(s) are dropping spark,then switch boxes,go for another run and see if the spark drop has switched to different plug(s).If that's the case switchbox gone and it is recommended to replace both.The easier option,is to borrow two known to be good and try them.Then replace both If it's not the case go back to the coil on the plug that's dropping.
    Last edited by haventaclue; 10-19-2010 at 08:23 PM.

  14. #14
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    Oct 2010
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    Default Re: 1987 Mariner 115hp In Line 6

    Yes the recitifier is new also and the charging system is working well. I have a timing light so I can perform the test you spoke of. I'm going to go ahead and install a new trigger, with the $$ already invested what's another $120.00, still MUCH cheaper than replacing the outboard or taking it to a real mechanic, if the problem still exists I'll go thru the test you spoke of. May take you up on the crate of beer either way. I really appriciate the help and advice. I'll let you know how it goes when the new trigger arrives.

    Some more information that may be helpful, the engine never dies just boggs down from WOT, I can idle along for a bit and it will open up again until it reaches max rpm and then the cycle starts all over again. Purrs like a kitten at low speed all day long if you want it too.

    By the way, I checked compression early on and it's perfect so I'm sure it's worth repairing.

  15. #15
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    Default Re: 1987 Mariner 115hp In Line 6

    I think you may be able to use a DVA meter to check the coil,I don't think it is either the trigger or switchboxes,if one of the switchboxes were gone I think she would be running a lot rougher or not at all.If the trigger was done she would be dropping spark at idle as well as wot.
    So that leads me to thinking about losing vacuum in the crankcase,a bottom seal going,a crankcase gasket or sucking air somewhere on the crankcase.There is a tube from top of the crankcase to the bottom,crack or hole in it

  16. #16
    Join Date
    Oct 2010
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    Charlotte, NC, USA
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    Default Re: 1987 Mariner 115hp In Line 6

    Now that is a different line of thinking. I understand a 2 cycle engine crankcase must be sealed to create it's negative pressure to run, however I can't see how this would alow it to run for the first 30 minutes or so until it gets hot. I've had smaller engines (chainsaws, weedeaters, etc) with leaking seals and they usually won't rev up or sometimes, even start if leaking bad enough. I don't mean to dispute your advice, but have you seen a leak showing up only after the engine has been run for a while? I will certainly pursue that avenue it you've seen this. Need to get her fixed up.

    The tube you are referring to has been replaced, I replaced all the rubber early on, ie fuel lines, vaccum lines, primer lines, and also the cross tubing, even replaced the one that shows the water pump is working on the side of the engine cowling. I suspected an air leak first off, but have ran it and sprayed starting fuild around all seal areas (which should effect the running if leaking) but found no problems there.

    This type of brainstorming will solve the problem, lets keep it up. Thanks

  17. #17
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    Default Re: 1987 Mariner 115hp In Line 6

    You're correct in saying that it wouldn't run at idle and it would be difficult to start,back to the drawing board

  18. #18
    Join Date
    Sep 2010
    Location
    ontario
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    9,848

    Default Re: 1987 Mariner 115hp In Line 6

    What about the " bleed inserts "--------------- found inside the transfer covers???????

  19. #19
    Join Date
    Oct 2010
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    Charlotte, NC, USA
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    Default Re: 1987 Mariner 115hp In Line 6

    You're referring to the two check valves (top and bottom) that the bleeder hose connects to??

  20. #20
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    Default Re: 1987 Mariner 115hp In Line 6

    Nope, racerone is referring to the small plastic insert found in here,five in your motor http://www.themarinedoctor.com/cgi-b...num=1254675223 they drain excess fuel down through the block and lubricate the lower and upper end bearings.They have a habit of getting sucked in or blown out of their place

  21. #21
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    Default Re: 1987 Mariner 115hp In Line 6

    Idle curiosity,are the plug leads the original? If they are,I wonder if the have a copper core or carbon?

  22. #22
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    Oct 2010
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    Charlotte, NC, USA
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    Default Re: 1987 Mariner 115hp In Line 6

    They are not the orginals, I replaced them during a regular tune up several years ago with copper wires, not carbon and all the spark plugs are new (guess you assumed that) replace the easy stuff first kinda thing.

  23. #23
    Join Date
    Oct 2010
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    Charlotte, NC, USA
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    Default Re: 1987 Mariner 115hp In Line 6

    Since your being so helpful, let me fill you in on the past history, I bought it new in 1987 in 1998 the wonderful autoblend system failed and locked up the power head, the entire powerhead was replaced then (done by the dealer it was bought from) Two years ago it developed a leak (water) around the exhaust plate so I replaced the inner and outer gaskets and properly torqued all the bolts, no more leaks. Has ran fine ever since till now. When this bogging down problem started I suspected fuel delivery, cleaned and rebuilt carbs, replaced the fuel pump and all related fuel lines all the way to the tank (autoblend no longer exists). This brings us to today, you know the rest. New stator and new recifier and 6 new spark plugs, but the problem is still here. I fish tournaments regularly so the outboard has some hours, I wish my outboard mechanic skills were as good as my bass fishing skills, I do okay at wiegh ins. Hope that helps some. When we get this problem solved I'll buy the crate of beer.

  24. #24
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    Default Re: 1987 Mariner 115hp In Line 6

    You can count the fish that I have caught in single digits.I was fishing of the port side,caught four.Brother-in-law on the other side,caught twenty,we were both using the same bait??????????.But that's not solving your problem.
    This is why I don't think it's the switch box.If one switchbox has gone,you would only be running on three cyls,I think it would run very rough if at all at idle on three and you say she runs sweet at idle.
    Here's my thinking on what's happening.You're boating along,motor warms up,something expands,whether it's a wire or component,until motor bogs,you back off to idle for a while,expanded part cools enough to allow you to go wot for another little while then repeats.
    When you replace the trigger and it solves the problem,I hope it does,if it doesn't it's time to start looking for bare wires,daft question,running premix 50:1?

  25. #25
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    Oct 2010
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    Charlotte, NC, USA
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    Default Re: 1987 Mariner 115hp In Line 6

    Yes have been premixing since the autoblend failed back in 1998, 50:1 sometimes a smidge rich but never lean. And yes idle is sweet as can be and will idle all the way to the dam and back if you want (about a 7 mile trip), Starts up easy too. Trigger tracking number says it will be here tomorrow, I'll install and hit the water. Hope to give you good news tomorrow evening.

    Oh and even if using the same bait you have to hold your mouth right (my papa always said that) : )

  26. #26
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    Default Re: 1987 Mariner 115hp In Line 6

    Must try that

  27. #27
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    Oct 2010
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    Default Re: 1987 Mariner 115hp In Line 6

    Thought I'd give the old trigger a test, manual says ohm readings are between 11- 14 between each of the three sets of leads, they all check good. I used your "heat it up" trick and two of them still check good the other set goes to 17, so I'm hoping this is the trouble. I don't have any specs for the switchboxes, manual says can only be checked with a Mercury analizer. I'll keep you updated tomorrow. Keep your fingers crossed. What part of the world are you in?

  28. #28
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    Default Re: 1987 Mariner 115hp In Line 6

    If everything else checks out it's the switchboxes
    Ireland,God's country. It's after midnight,goodnight

  29. #29
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    Default Re: 1987 Mariner 115hp In Line 6

    Ok, well the trigger was no help, problem still exisits. However, I suspected fuel problems from day one, but have replaced fuel pump all fuel lines, filters, etc. Even checked the pick-up tube in the tank and all is okay. With that said, it still just acts like it's starving for fuel to me. What's your thought on getting a portable tank (we call them a johnny tank) and taking with me. When the problem starts connect the johnny tank and see if the problem goes away???. Today when it started bogging down the primer bulb was collasped, and I've never had a boat do that, as if it was "sucking" so hard it collasped.

    My next item is the swithboxes on the ignition side, but I'm hard pressed to think they are the culprit here.

    I ready to ship it to Ireland and see what you can do with it.

  30. #30
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    Default Re: 1987 Mariner 115hp In Line 6

    Do Do Do .Fuel. OK.Defiantly try the portable tank. When the primer collapsed that is a sign of a blockage between the pick up and the primer,the pump is sucking but nothing coming through.Have another look at the diaphragms on the fuel pump.Did you the same bore of fuel line?Bigger is better.I speak from experience on this,new line,smaller bore by .120th/2mm ,one and half miles out in the Atlantic,give her all she got and started to starve,eased of the throttle and back to normal.One very pale ever patient wife.
    I would clean the tank, check the pick up and put in a new primer.And put the old trigger on ebay.I still think that she would not idle sweet if one of the switchboxes were out.Though I have been known to be wrong before.

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