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Shudder

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Bruce53

Member
Hi Guys...
After replacing my drive shaft bellows I took the boat for a sea trial. No leaks and all looked fine so I started a normal acceleration and when I passed 2000 rpm there was a rather vilant shudder in the boat that I had never felt before. I slowed the engine immediately to an idle and began increasing rpm slowly. It went up to 3500 without any shudder and operations since have never felt the shudder. The shudder was not an unbalanced prop; it was much slower than the prop speed. Can anyone guess the problem? Was there a "grabbing" in the U-joint column somehow? Many thanks for any help on this one....
Bruce
 
What docksidemarineservices has suggested could very well be the case. I have gone through 2 props already in the back bays in Cape May and Wildwood New Jersey. In other words, looks like alot of water doesn't it? Problem is this: Most of the bays during low tide are nothing short of reflection ponds and water less than two feet deep. I had drive trimmed up as far as possible and still almost got stuck in one or two spots. One prop hit was caused by trim pump acting up and the other was just operator error (lol). Don't know if you are even running in salt water but you may have hit bottom or something semi submerged without knowing it and or doing any real damage to prop until you were past the object. Could also be as kghost suggests with maybe some water passing through system and causing engine to stumble. Hard to say, could be alot of different things. jmho all the best, Tom
 
My engine had a bad shudder and it turned out to be a spark plug not working. My 6 cylinder was only firing on 5. If yours only shuddered once I have no idea what it would be. Check your plugs and see if one is partially broke or discolored from the other ones.
 
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