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LS 2000 Motor Help

Shane Ratliff

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Yamaha
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I bought a clean LS 2000 this year and it started acting up the last weekend we were on it. One motor is hard starting when cold but seems to run well once started. The 2nd motor starts fine but wont rev into the power band. Neither motor smokes much once warmed up. I had a compression test done, by a boat mechanic, and all 6 cylinders are 100-107psi with 2 different gauges and he is recommending rebuilds immediately. I am already in the process of having the carbs rebuilt and oil lines replaced with clamps. I was always told if all the cylinders psi are close and the motor seems to run ok to leave them alone. Do you guys think I need to have the motors tore down or replaced now? I was expecting to do the motors in the next year or two but I just bought the boat cash and don't have a lot of reserves left after committing to the carbs and oil lines. Thanks
 

4x15mph

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I wouldn't rebuild with those numbers as you said. Carburators should definitely be cleaned and rebuilt unless you know they were done recently and you should consider using the more expensive OEM parts.

Its hard to diagnose your issue but given it is new to you, I would start with fuel (carbs, filters, check lines) and air.

Great boat! Enjoy it
 

Shane Ratliff

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The carbs haven't been rebuilt in many years so I have already ordered the Mikuni rebuild kits for both motors along with new oil lines and clamps. Thanks for the info.
 

4x15mph

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The carbs haven't been rebuilt in many years so I have already ordered the Mikuni rebuild kits for both motors along with new oil lines and clamps. Thanks for the info.
Consider removing the OEM fuel filters and putting Sierra water/fuel filters. Easy to replace each year and they remove water from your fuel
 

Beachbummer

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With the carbed engines most power related problems...it's the carbs. Best of luck! I second the Spin On Water filter suggestion, it will lengthen the life of the carbs!
 

treeskier

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2016
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The engine that is a hard start may actually be related to your pump and impeller housing. In the OEM pump housing the tubes were lined with metal ... aluminium i'd guess. Over the years as water gets to them...particularly salt water they swell slightly and rub the impeller causing a hard start. When the engine ran a while pumping water through the housing the metal sleeve contracted enough for the engine to function close to normally when warmed up...even on subsequent non-cold starts. The replacement pump housings have a plastic sleeve rather than metal which solved the swelling issue.

On the engine that wont hit the power band but has good compression I'd look at the exhaust manifold...you may have the beginnings of a deteriorating exhaust manifold and if you've been lucky enough to catch it before your have a cooling issue you may have saved your motor. Another indication of this is if you have a weak stream from one of the pee holes but not the other...especially at low rpms. When I ultimately fixed the problem the increased flow was very noticeable.

Good luck...BTW I had both issues in my 2002 LS2000...I was not fortunate enough to figure out the exhaust manifold before I fried 2 of 3 cylinders.
 

Shane Ratliff

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I ended up rebuilding both top ends and carb kits. Everything seems to run fine so far but I will find out for sure this weekend on the lake
 

treeskier

Jetboaters Commander
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Great hopefully everything runs well for you. I graduated to a newer 24ft 4 stroke but I’m visiting the old boat this week at my girl friends son’s house so we’ll hopefully get some 2 stroke smoke for old times sake.
 
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