Mercury 90HP 2-Stroke - What is this

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    Posted: 26 May 2022 at 5:26pm
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Ok I'm stumped. 
I have the above motor and it is idling perfect but will not accelerate as it misfires badly. When I took the cover off the motor I found this 20*3mm item. The brass colour may be a cooper coil. Like a solenoid plunger, unusual fuse or similar.
Ideas?
PS. I am having trouble posting the photo. I will try again.
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Post Options Post Options   Likes (0) Likes(0)   Quote Mo-Mac1 Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 2022 at 5:28pm
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Post Options Post Options   Likes (0) Likes(0)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 2022 at 5:31pm
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Where did you find it. I have same motor - not seen that.
Could be a number of things causing problem.
Has it just happened? What has been done to motor?
Alan
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Post Options Post Options   Likes (0) Likes(0)   Quote Mo-Mac1 Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 2022 at 6:15pm
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It was sitting on the outside of the power head in the cowling on the fuel pump side of the motor.
It was running perfect 2 weeks earlier. So after the fault I have:
Striped and cleaned carbs, replaced fuel pump diaphragm.
Checked timing and carb settings.
New magneto/coil under the flywheel.
Check flywheel magnets.
Tried disconnecting sparkplug leads but all 3 have a similar effect.
2 of the 3 cylinders seem oily.
Compression test all 3 are the same, about 118 psi.
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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 May 2022 at 12:12pm
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It could be fuel starvation. Sounds like you know what you are doing.
One thing to do is fit a clear piece of line from the outlet of the engine fuel filter to the carb - about 75mm long. Run it at idle and see if any bubbles - air getting in the suction side.
Also check that filter is not blocked.
I have no idea what that piece is - I have had near everything of my motor over the years, never seen it before. maybe something loose that was rolling around for ages?
How did you check carb settings? Faulty settings can do it - hesitation under power. Usually done under load. But the book says wind in idle screws (air bleeds) until engine note changes (too rich), then back out 1/4 turn.
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Post Options Post Options   Likes (0) Likes(0)   Quote Mo-Mac1 Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2022 at 10:37pm
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Thanks Alan. I will have a play with some of your ideas. It seems odd that a picture like the one above does not trigger anyone to know what it is. 
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Post Options Post Options   Likes (0) Likes(0)   Quote smudge Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2022 at 5:22am
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It looks like a small inductor which is used as an electrical filter on something like an old tv or radio. Is the copper colour a fine copper wire wound around a ceramic spool? I can't say I've ever seen one on an outboard. If it is that then my guess is its from something else that's found it's way in there.
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Post Options Post Options   Likes (0) Likes(0)   Quote Mo-Mac1 Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2022 at 5:35am
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Yep, We think it is fine copper wire/inductor. But I don't leave the cover off the motor and cannot see how it ever got there. I will try to ignore it. Thanks guys.
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Post Options Post Options   Likes (0) Likes(0)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2022 at 1:53pm
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I have had near everything off my Merc (s) 90 over the years. I don't believe it belongs in there.
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Post Options Post Options   Likes (0) Likes(0)   Quote smudge Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2022 at 2:18pm
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Likewise I have had a Mercury 50into every conceivable piece, nothiong like that in one of those.
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Post Options Post Options   Likes (0) Likes(0)   Quote Kandrew Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2022 at 4:48pm
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Can you check your main charging fuse, the photo may not look like a normal fuse but the engine not running above idle can point to a fault in the charging system. There’s a main fuse in the regulator side and if this blows or the regulator is faulty the charging system will produce to much voltage for the coils and won’t run above idle.

On later model motors this fuse was replaced with a fusable link. Older motors had a 50 amp fuse which did look at bit like this.

Just to check you haven’t replaced the battery with the wrong type of battery like a gel cell or a house battery, this can damage the regulator as these batteries need to be changed at a lower rate than a standard start battery.
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Post Options Post Options   Likes (0) Likes(0)   Quote smudge Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2022 at 5:21pm
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Yes it could well be a fuse,20 x 5 is standard size from memory. It doesn't look like a fuse but anything could have been used. A fuse would almost always have its rating embossed on the end caps
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2022 at 6:06pm
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"On later model motors this fuse was replaced with a fusable link."

Cool that may answer a question I dont need to know, but may in the future.
I had a couple electrical issues with my Jonny tilt...Alsorted.
I followed the whole circuit diagrams around see how stuff works..
In there I rem a fusable link inside the loom. Is this what they look like?



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Post Options Post Options   Likes (0) Likes(0)   Quote Kandrew Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2022 at 7:15pm
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Originally posted by Steps Steps wrote:


"On later model motors this fuse was replaced with a fusable link."

Cool that may answer a question I dont need to know, but may in the future.
I had a couple electrical issues with my Jonny tilt...Alsorted.
I followed the whole circuit diagrams around see how stuff works..
In there I rem a fusable link inside the loom. Is this what they look like?



Steps this is not a fusable link I think it’s an early main fuse from a late 90ies motor.

A fusable link looks like a thin piece of normal plastic coated wire and normally yellow or white in colour around 150mm long. It will have a lucar spade type terminal on each end with a plastic cover or it will be crimped into the loom with heat shrink on the ends.

When you cut it, it looks like a whole lot of the old fuse wire strands, not made from copper. Fusable links are used for higher current draw areas.
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Post Options Post Options   Likes (0) Likes(0)   Quote jackel Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2022 at 8:20pm
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Hiya, I have had very similar symptoms with a 40hp ELPTO (two stroke) mercury. As soon as I put it in gear it would stall, or move forward briefly and stall. I managed to drain the carb while on the water, which was enough to get me back to the ramp. I put it down to water in the fuel or stale fuel. I got the fuel from the campground tank. Have you tried draining the carb, and connecting up a fresh tank of gas? The gizmo you found could be a red hearing, have no idea how it got there or what it is. Smudge has really good knowledge of electrical systems etc, and has stripped a similar motor so I would count that out. Worth a go anyway....
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Post Options Post Options   Likes (0) Likes(0)   Quote Foxtrot Oscar Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2022 at 3:05am
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Originally posted by Mo-Mac1 Mo-Mac1 wrote:

It was sitting on the outside of the power head in the cowling on the fuel pump side of the motor.
It was running perfect 2 weeks earlier. So after the fault I have:
Striped and cleaned carbs, replaced fuel pump diaphragm.
Checked timing and carb settings.
New magneto/coil under the flywheel.
Check flywheel magnets.
Tried disconnecting sparkplug leads but all 3 have a similar effect.
2 of the 3 cylinders seem oily.
Compression test all 3 are the same, about 118 psi.


No mention of actually 'replacing' the sparkplugs.
That can be a cause of misfiring and is an easy elimination.
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Post Options Post Options   Likes (0) Likes(0)   Quote Mo-Mac1 Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2022 at 5:48am
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Thanks guys,
I have replaced spark plugs as a trial.
I have been working crazy hours this week but will focus on these thoughts on the weekend. Battery is about a year old and is a large standard starting battery and is in great condition. I will focus around the charging system. Thanks.
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