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The Boat Is A 1900xl Norriscraft With An Adjustable Duetwieller Jackplate With A 24p Throphy 4 Blade Prop. Boat Dont Seem To Miss At Wot But Wont Go Past 4800 From 3/4 To Full Throttle Rpm Doesnt Change. Seems To Run Smooth Untill Backed Off To 3500 And Has Slight Miss. The Boat Has Done This Since I Have Owned It. I Have Owned It For A Year Now. I Believe The Boat Set For A Couple Of Years Before I Got It But I Really Don't Know. Thanks Just Trying To Figure It Out Before I Tear Up Something.
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most likely need to clean and/or rebuild carbs. check if bumping choke helps. -
Compression test?
Have you done a compression test on the motor? Do you have a Yamaha service manual for it? Make sure the compression is good in all cylinders (115-125 psi...) and all the linkages are adjusted to specs, including timing. Yes if the boat has set up for a long time without being run the carbs will definitely clog up, especially the idle jets. Maybe do a shock treatment of Seafoam to decarb the motor too. The big brass bolt looking things on the bowl sides of each carb are the main jets, the small brass things are the idle jets. The main jets will have an orange O-ring seal toward the tips, make sure this O-ring is not broken or torn. They're $5 each at the dealer. But in a motor that old you may find them deteriorated. As recommended before, when in doubt, a good carb tear down never hurts. If the fuel pumps are more than 5 years old I would replace them too. If you can't pump the primer ball up firm with the motor off, the fuel pumps are probably shot.
-MikeComment
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