Mercury 115 CT missing

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Post Options Post Options   Likes (0) Likes(0)   Quote Mc Tool Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2025 at 9:40am
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Originally posted by Keith C Keith C wrote:

Might need some popcorn while we "spectate". 😄
yeah I was just thinkin this might be worth watching ( and I was also thinkin FFS ! put  new plugs in it , or even just one and move it round the cylinders to eliminate any faulty one  ).
  And whoever said about the crack on the lead opening up when its hot ...........lemmie tell ya Smile, as a retired EST  , if there is a crack or pin hole in the HT lead temperature wont make a 5hit of difference.Smile
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Just a question is the fuel bulb still hard when it starts to miss. Might be a fuel pump issue.

Just another thing don’t go playing around with the HT leads while the engine is running or you’ll find out the hard way why they are called HT leads.

When I was working full time on outboards, I had a spark plug with a big alligator clip welded in it so when I was trying to diagnose engines with misses I could drive along the the cowling off stop when it started missing, switch the motor off and pull the HT lead of the cylinder I thought was missing plug it onto my spark plug clipped on to the engine somewhere and start the engine to see if there was spark at the plug

That leads me to another question what happens if you switch the engine off wait a few minutes then start it back up, does it still miss.
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Post Options Post Options   Likes (0) Likes(0)   Quote Mc Tool Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2025 at 12:50pm
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Are  all the injector plugs on tight , had a car once with the clip broken off the injector plug , had to give it a wiggle every now and then .... even showed the Mrs how to do it LOL , ungrateful  cow seemed to think I should just fix it .
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Post Options Post Options   Likes (0) Likes(0)   Quote smudge Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2025 at 2:55pm
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Originally posted by Mc Tool Mc Tool wrote:

Are  all the injector plugs on tight , had a car once with the clip broken off the injector plug , had to give it a wiggle every now and then .... even showed the Mrs how to do it LOL , ungrateful  cow seemed to think I should just fix it .

How rude of her! It reminds me of the time(s) I showed my wife how to diagnose and replace a faulty coil on her Honda Accord. Apparently all the answers on facebook said it was 'something else'. Big smile
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Post Options Post Options   Likes (0) Likes(0)   Quote smudge Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2025 at 2:57pm
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Originally posted by Kandrew Kandrew wrote:

Just a question is the fuel bulb still hard when it starts to miss. Might be a fuel pump issue.

Just another thing don’t go playing around with the HT leads while the engine is running or you’ll find out the hard way why they are called HT leads.

When I was working full time on outboards, I had a spark plug with a big alligator clip welded in it so when I was trying to diagnose engines with misses I could drive along the the cowling off stop when it started missing, switch the motor off and pull the HT lead of the cylinder I thought was missing plug it onto my spark plug clipped on to the engine somewhere and start the engine to see if there was spark at the plug

That leads me to another question what happens if you switch the engine off wait a few minutes then start it back up, does it still miss.

Great question Kandrew
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Post Options Post Options   Likes (1) Likes(1)   Quote kimber7wsm Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jan 2025 at 6:11am
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Mc Tool, if you read my reply, you see I specifically said that I had experienced this. So your experience is very different to mine. And I know mine is correct because it happened. I did miss saying turn off when removing lead, something I am remiss for. My advise stands.
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Post Options Post Options   Likes (0) Likes(0)   Quote Mc Tool Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jan 2025 at 8:35am
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Originally posted by kimber7wsm kimber7wsm wrote:

Mc Tool, if you read my reply, you see I specifically said that I had experienced this. So your experience is very different to mine. And I know mine is correct because it happened. I did miss saying turn off when removing lead, something I am remiss for. My advise stands.
   Once you have a crack or pin hole that goes from the inner core to the outer surface  of the insulation ( wether its pinched closed or pulled open )  the insulation is completely perforated  and there is no dielectric strength, all you have left is air gap  , regardless of temp . We are talking 10's of thousands of volts   and if you provide an alternate path to earth via said perforation ......like put your finger on it  ..... it aint going to matter if its hot or cold .Smile 
Its like a hose  with a pin hole thats closed over . If you put 10psi into that hose it may well not leak at all  but if you put 40,000 psi ( like 40,000v )  it will .
 I dont doubt for a second that this happened as you said , all Im sayin is that temp is pretty much irrelevant in this instance .Smile 
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Post Options Post Options   Likes (0) Likes(0)   Quote smudge Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jan 2025 at 10:00am
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Humidity and temperature are kind of related so it is certainly possible
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Mine had an issue with missing about 200 hours into its warranty. The gear position sensor died, and when watching the forward, neutral , reverse display on the Vessel View, it was intermittently changing from forward to neutral to reverse, often doing at trolling speed. So it was thing I was trying to change from forward to neutral or even revs at too high a revs. So the engine limiter was kicking in. As the Sesnor got worse the issue would happen at run speeds. It turned out to be a bad batch of sensors, and I know of a number of boats that had the same issue about the same time. 

Your engine is a couple of years younger than mine, and I didn't have the issue with it in idle. so may not be connected. You're just going to have to visit a dealer I'm afraid.
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Post Options Post Options   Likes (0) Likes(0)   Quote kimber7wsm Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jan 2025 at 6:36am
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It is also possible for the conductor in the lead to crack without the insulating layers to crack. Thermal expansion and contraction can happen in that case. Say what you like. I've see it physically happen.
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Originally posted by kimber7wsm kimber7wsm wrote:

It is also possible for the conductor in the lead to crack without the insulating layers to crack. Thermal expansion and contraction can happen in that case. Say what you like. I've see it physically happen.
Had a motor that ran perfectly for 20 minutes at fast running then would stop,cool down and go for 20 minutes,resistor/capiuctor was heating up and connection breaking. Even took the mechanic awhile to figure out was happening.

Joys of technology. Big call for younger people in industry as trhey have caught up on new technology.A lot of the older people still stuck in theirs ways. Just dont understand how new stuff works. Hence why boy is off to kiwirail to work on hybrids,old farts dont understands cambus! Even outboards have itr.
"Times up"
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Post Options Post Options   Likes (0) Likes(0)   Quote Mc Tool Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jan 2025 at 8:49am
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Yes  individual components on a circuit board  like capacitors , resistors  , triac's  , diodes  bla bla bla can fail as they come up to working temp  or overheat . Symptoms as you describe , and given time to cool will often work again . We used to refer to these parts as "wounded "
This applies to any circuit board  be it outboard , TV  or whiteware.
 Now days we are expected to cough up hundreds of dollars to replace a whole circuit board  when there may only be a 50c  part thats actually failing . By spraying  instant freeze  on the whole board the thing will often start working  and if so  wait till it heats up and fails  and then give each individual component  a wee squirt of instant freeze  and you can often identify either a faulty component or a dry joint , and that component can be replaced  ( using appropriate heat sink and static protection  )
kimber7wsm , sounds like your inviting me to call you a liar  , but I dont think you are ( and I have no wish to offend you either ). I didnt come here to win arguments   or be smarter than everyone else.........  so I dont mind if you think Im wrong here . Lets just get on with helping each other  where we can Smile.
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Post Options Post Options   Likes (1) Likes(1)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jan 2025 at 10:31am
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The problem is the cost of tracking those failed components vs the cost of the unit.
My Banax 1000 elec reel failed last yr. It has done a lot of work, could not really complain. But I figured there had to be a reason. It would light up etc but not respond to the wind instruction.
Finally decided to rip it apart, nothing to loose. It had a sealed circuit board which I finally got to and tested various components. Bingo. Failed Mosfet. Once located, was a $10 part. Works great again. But it took some time to get there. So this stuff gets dumped for lack of ability to repair and cost of someones service time - prob in the order of $100+/hr? If I charged my hrs out to myself, would have been cheaper to buy another Banax.
Working on a mates 911 right now. High rpm miss. Fuel or spark. Not sure - going thru various tests. The answer will be there to be found. But it is the time it takes. Mine is free, for my mate.  I may, or may not, be slower than a certified garage (I know these things inside out), but you can clock some big bills up pretty quick at over $100 hr to find a fault in something..
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Post Options Post Options   Likes (1) Likes(1)   Quote Kandrew Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jan 2025 at 11:33am
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Alan to work on a Porsche you’re talking more like $500 plus an hour.

When you look at my original trade as an auto electrician in the old days we had to fix everything as there were not a lot of replacement parts around, we rewound some armatures for wiper motors. Re taped field coils even changed bulb holders in brake and tail lights.

Lots of replacement parts around nowadays and they are cheap, computers have made engines more reliable and the basics easier to diagnose. There will always be problems that are a bit out of the box but a good marine tech will be able to isolate the problem through trial and error and normal find the fault.

I worked on outbounds and motorcycle for many years and there’s a completely different thought pattern between 2 stroke and 4 stroke. Different fuel systems, ignition systems fuel pump diapharms on 2 strokes are the cause of many problems and get it wrong and you will damage the engine.

Misses are relatively easy, is the problem electrical or fuel, when it’s missing what’s the fuel bulb doing. If it’s soft then the problem is normally on the supply side. If it stays hard then it’s on the input side.

Another good indicator of where the problem is checking which cylinders are running hot. If one cylinder is cold then to me that indicates an electrical problem. next check the plugs they will will soon show you which way to keep looking. If one plug isn’t burning clean but has good spark, check the compression. Remember 2 and 4 stroke have different compression ratios. If it’s an EFI and the compression good look at the injector.


Just keep following the process through. But for me even when I was racing cars and boats the plugs are the eyes to what’s happening with the motor.
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Post Options Post Options   Likes (0) Likes(0)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jan 2025 at 12:06pm
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Totally agree with your thoughts and the fuel bulb suggestion as well. yes - cylinder temps are good indicators for misfires.
My trusty VN holden (350+km) developed a misfire acouple of weeks ago. Ran pefect when cold, when up to temp had a miss, especially under load.
Turned out to be an HT problem. They are heat sensitve systems. Never threw a multi meter at the HT leads - waste of time - didn't fit the symptoms and likely to give a misleading result.
I am still racing cars. Not sure when that will end. Hopefully not with a big crash :-).
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Yeah , I keep forgetting the labour costs  with these things . When I stopped working in 09 we had just started charging 80 bucks /hr  to service whiteware .That stems from  me fixing everything , I mean I got all day , look on the net , Bobs yer auntie , worth a crack Nigel,  AND its a wonderful excuse to buy....... "MORE TOOLS? " she cries   ( LOL how well do I know that face ) .
 Like your Banax reel Alan  , if you have the nouse  there is so much that can be fixed  for whoever you want to help out . Case in point my 18hp Tohatsu .... got it for free coz it was rooted  according to the owner  . Im going to wind up with a better than new  ( every bush , bearing , bolt, seal , short block electrix and a proper paint job ) outboard for well under a grand . My stupid rich lawyer brother Big smile paid way more that that just to get his boat serviced .
Done a few cam belts  and oil changes  for friends  , box of beer dozen eggs sort of thing  Smile 
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Post Options Post Options   Likes (0) Likes(0)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jan 2025 at 5:21pm
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The problem with the later Gen stuff - like the Merc 115 is you need the laptop diagnostic programmes. Yes - there is some stuff you can do, and yes, there is some it won't tell you - as was mentioned earlier - no sensors for the HT leads. But some of them can pick up a HT miss.
But you are left with just a few basics to check. An HT lead breaking down under heat would be a pig to diagnose, and some hrs (ss clocked up).
I just ordered today a Yam 70 4S to replace one of my trusty reliable Merc 90 2 S. Reluctant to say goodbye to it - but at 2500 hrs, I need to do something. Never missed a days fishing with it. The 4S with a black box does worry me. I guess I will cope.
The 911 is sorted - coil.
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Post Options Post Options   Likes (0) Likes(0)   Quote Got-ya Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jan 2025 at 6:02pm
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Thats a pretty big drop in power along with the lack of 2S grunt. Hope it works out OK.
THERE ARE TWO KINDS OF FISHERMAN, THOSE WHO FISH FOR SPORT AND THOSE THAT CATCH SOMETHING.
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Post Options Post Options   Likes (0) Likes(0)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jan 2025 at 7:16pm
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I did post a query on this forum about 6 mths back - along those lines. not too many replies but I have since run into a couple of guys running same on similar weight boat. The one reply on this forum was also very positive.
Agree it is a punt - but I really don't use my 90 HP. I never really run over 3500. And I am doing as much knts as I would want the hull to run, and most times I can't run at that speed.
I think it will work out OK. Fingers crossed. It is the same (slightly less) weight as my 90. The next step up is another 40 kg.
But I think the point is, I would be putting 40 kg extra weight on for HP I wouldn' t be using.
I have to conceed - at this point I don't know, but at some point a few months ahead I will know if it is the right call. Being a smaller motor I am quite prepared to invest in a 2nd prop and change it when the load rating changes - eg a couple of mates coming over to fish for a few weeks. otherwise, it is 90% solo.
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Post Options Post Options   Likes (0) Likes(0)   Quote Mc Tool Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jan 2025 at 7:28pm
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Mmmm 2500hrs is about 160,000kmin car years  so I spose that is getting on a bit . Just for interest sake , I get the notion that your well capable of maintaining an outboard and thusly its probly better than most its age , but other than the hrs is it showing signs of age / wear .  Just trying to get my head round this hrs thing . 
I bought a 90hp 2/ yam that I was assured by the dealer had less than 10 hrs on it , and I can remember thinking that was bugger all . I didnt have an hour meter  but I figured that at  20l/hr ( it was surprisingly consistent ) I would get 2 1/2 hrs from a litre of oil  and I reckon I put 12l of oil thru that motor . 12 times 2 1/2  is 30 ......30 hrs . That surprised me coz it felt like I was superglued to that boat ...... and I only managed 30 hrs  . Then I get you with your 2500 hrs  Big smile make me feel like a friggin amateur , but I now get a better handle .
 What sort of oil do you use ?  I always went for the TCW3 Valvoline outboard oil , and I love the smell of 2/ smoke  so I  was in nirvana there . 
I wish I was young again .... Id be heaps smarter than this time
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