Problem with Yamaha Mariner 40HP Engine?

amoore658

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Joined
20 Dec 2009
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Northern Ireland, GB, UK
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Hi,
I have a Two-Stroke 40HP Yamaha Mariner outboard engine and recently, I've noticed when it's on cruising speed the engine shudders - its speed decreases slightly, but there is a bad shudder of it. The way I've found to correct this is reduce speed, and gradually increase again - this gets rid of the shudder, but only temporarily and then it comes back.
What could be the possible cause for this?
I've checked the water cooler flow out of the engine, and it's normal.
Thanks for your help
 
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