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Old 29 June 2019, 14:57   #1
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Mercury 15 - trouble starting - this is cracked?

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Been having trouble starting a mercury 15hp, on inspection this part is cracked... could anyone advise on what this part is called? Many thanks
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Old 29 June 2019, 15:00   #2
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They are your coils. The crack could allow the spark to leak to earth.
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Old 30 June 2019, 02:47   #3
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They are your coils. The crack could allow the spark to leak to earth.
Thank you. Iím new to outboards, any idea on where to get a replacement? Simple fix? Or would I be better taking this to a specialist.
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Old 30 June 2019, 02:53   #4
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Prety easy to change just a straightforward swap over parts should be available from any merc dealer
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Old 30 June 2019, 03:16   #5
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Looking at this again... do you mean this OB isn't a great starter or it won't start at all?

This could be your problem or it could be coincidental. You could remove the coil, clean it with a barely damp rag and dry properly it in a warm place. Then fill the cracks with silicone sealant which will insulate and see if that makes a temp repair.

Somewhere online there are electrical test figures for the Mercury 15 2-stroke ign system and you could check your coils.

There were two different colour coils fitted to this OB range. Earlier ones (say 2000 and before but just a guess) had blue coils like yours and later ones black coils. They may be electrically different but I don't know so check out before buying.

Finally note the two coils have different lead lengths. Again I'm not sure if the leads are integral to the coils or can be changed but if they are integral don't buy a short one if you need the long side... I think it is the long side to lower cylinder you are showing as cracked. You can check if the leads can be changed over I'm sure by removing the cable tie and pulling the rubber caps back.
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Old 30 June 2019, 03:34   #6
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Here's than OE repair manual online... http://www.baads.org/wp-cms/wp-conte...nual_PART1.pdf

Section 2 for ign and the coil test figures are in the spec table. I see they mention a pre/post 1999 ign system change but not clear if the coils are physically different... dealer or online parts listing for your serial number would sort that. They seem to have the same test figures across those years anyway.

Info in that manual does seem to show the coil leads can be swapped if the length were wrong.

Edit: Should have asked if you've done the basic checks... taking plugs out and earthing then pulling over looking for a spark... seeing if plugs wet or dry etc.
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Old 30 June 2019, 05:41   #7
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Originally Posted by Fenlander View Post
Looking at this again... do you mean this OB isn't a great starter or it won't start at all?

This could be your problem or it could be coincidental. You could remove the coil, clean it with a barely damp rag and dry properly it in a warm place. Then fill the cracks with silicone sealant which will insulate and see if that makes a temp repair.

Somewhere online there are electrical test figures for the Mercury 15 2-stroke ign system and you could check your coils.

There were two different colour coils fitted to this OB range. Earlier ones (say 2000 and before but just a guess) had blue coils like yours and later ones black coils. They may be electrically different but I don't know so check out before buying.

Finally note the two coils have different lead lengths. Again I'm not sure if the leads are integral to the coils or can be changed but if they are integral don't buy a short one if you need the long side... I think it is the long side to lower cylinder you are showing as cracked. You can check if the leads can be changed over I'm sure by removing the cable tie and pulling the rubber caps back.
Thank you for this, great help. Itís running fine once itís going. Some times it starts first pull. Flushing it yesterday and it ran for around 10 minutes then just cut out. Couldnít get it started after that... nothing seems seized it just canít quote get going off the pull. I canít seem to find the blue coils anywhere online, will another fit? I will take it off and try sealing it as you advised first though.
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Old 30 June 2019, 05:49   #8
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I’ve searched my serial number and nothing seems to come up... it’s 09701570 - I think I could replace the part if I knew what to order ha ha.
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Old 30 June 2019, 07:01   #9
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It may be co-incidence but if you go to the following website:

Marine Engine Parts, Spares & Repairs | Holes Bay Marine Poole, Dorset

you can select Mercury and 15 and then if you ignore the first zero, your serial number does seem to fit an available serial number range.

I've never used them but I'm looking round for a spares kit for my 15hp Mariner and happened on this website.
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Old 30 June 2019, 10:05   #10
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Had a look at the Holes bay parts listings. Seems whichever of the serial number ranges of the mid 1990s on models you try be it a 15, 9.9 or XR10 they all come up with the same coil part number at about £46 plus VAT.

As you say you will do I'd really want to try re-sealing the existing coil as a test first as I'd have expected it to cause perhaps rough running/idle or a misfire if intermittently earthing through the crack... but not cutting out totally after ten mins as it should just be capable of chugging along on one cyl.

There are so many things that could cause your problem such as heat soak failure of flywheel coil/CDI unit or the fuel system blocking (tank bleed open and OK?) or pulling in air.
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