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Old 10 September 2018, 02:46   #1
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Yamaha 200HP HPDI 2 stroke

Hi was about to go for a spin yesterday but upon firing up my engine didnt feel or sound very happy, stalled a few times on tickover, a bit more vibration than normal and sounded like it was perhaps missfiring a tad. I didnt want to tempt fate so gave up on going out that day. Very similar to an incident about 2 years ago which was diagnosed with coked up plugs/cylinder.

Apparently these engines don't like spending too much time at low speed, as I use my boat alot and as its in Holes Bay every time I venture out I spend probably a good 45mins at below 10 knots and probably half that time at 6 knots.

Last time I had the plugs changed and gave it a good blast and all was well again. I am going to change the plugs this week and see if that improves it, my question is have others experienced this with 2 strokes or this engine model and also is there any procedure for trying to prevent it happenning along the lines of when returned and at pontoon give it a good rev for a minute while in Neutral. ?
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Old 10 September 2018, 04:27   #2
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http://pacermarine.co.uk/product/qui...cleaner-355ml/

Iíve used this product before when I had a mercury Optimax
Might help remove the build up of carbon
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Old 10 September 2018, 15:35   #3
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Seems to be the way. As mine eats plugs at slow speed. There was a change to the plug on my 250 to a hotter plug, might be worth seeing if your was changed. I did a decoke about 6 months ago as per one of the USA forums, and now add some to each tank and it seems better although I always carry a set of brand new plugs.
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Old 10 September 2018, 15:38   #4
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Seafoam is the stuff I use as seems to be what they use in USA which is where most of these engines seem to be used
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Old 10 September 2018, 15:54   #5
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plugs went from 7eku to a hotter 6eku by the looks of it. Worth checking what you've got.
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Old 10 September 2018, 16:59   #6
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Don't imagine that revving at idle will help much - because half the cylinders are disabled when in neutral.
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Old 11 September 2018, 16:11   #7
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Yep, 4 of 6 work in neutral, and pretty sure if you Rev above 1400 it kills another 2. I'd start with plugs, and if you have YDS check TPS and O2 sensor. If you've not changed LP pumps in last few years I'd replace diaphragms sooner than later.
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Old 11 September 2018, 16:24   #8
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Yep, it was the plugs, inspected them and they were all black, oily and gunky. I guess thats life with a 200hp 2 stroke and time adds up going slow through the harbour every trip.

Think I will just mark my calender and change all the plugs every 6 months from now on instead of yearly. They are relatively cheap.
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Old 12 September 2018, 03:17   #9
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Quote:
Originally Posted by boristhebold View Post
Yep, it was the plugs, inspected them and they were all black, oily and gunky. I guess thats life with a 200hp 2 stroke and time adds up going slow through the harbour every trip.

Think I will just mark my calender and change all the plugs every 6 months from now on instead of yearly. They are relatively cheap.
I would definitely also us Quickleen or Sea Foam on a regular basis(every tank fill) and also do a double dose 'shock' treatment initially. I always used QK on my Opti's , renowned fro carbonising up when doing a lot of low speed rolling ... clogging injectors and fouling plugs, and never had any issues. All squeaky clean .
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Old 12 September 2018, 11:17   #10
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I would definitely also us Quickleen or Sea Foam on a regular basis(every tank fill) and also do a double dose 'shock' treatment initially. I always used QK on my Opti's , renowned fro carbonising up when doing a lot of low speed rolling ... clogging injectors and fouling plugs, and never had any issues. All squeaky clean .
Thanks I will get some
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