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Old 07-31-2020, 01:08 PM   #1
lts70
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Default Lightened crankshaft pulley

I have a SOHC EJ25 motor in a boat that I am messing with. I have another thread going on trying to tune the ECU and did not want to muddy the water in that thread with this question.

I am wanting to see if a Lightened crankshaft pulley or Undersized pulleys would be a good option for my engine.

I am only running an alternator as the other accessories were not needed in a boat.

My flywheel has been lightened and balanced.

As far as lightened pulleys I am seeing, Agency Power, Perrin, Grimmspeed as popular. But cannot find much info on undersized pulleys.

Any advise would be appreciated.
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Old 07-31-2020, 01:41 PM   #2
Jack
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Why? These components are designed to help the engine accelerate. Boats are pretty constant power, so light weight rotating parts are a waste.
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Old 07-31-2020, 01:52 PM   #3
lts70
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Old 07-31-2020, 02:03 PM   #4
Samurai Jack
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Why are you making another post about your jet boat?

And, no, you don't need a lightweight pulley.
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Old 07-31-2020, 02:36 PM   #5
lts70
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I thought I explained it above, I wanted to separate the pulley topic from ECU.

The builder had the flywheel lighted by 10lb to help performance.

I just figured another 5lb would help as well.
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Old 07-31-2020, 03:50 PM   #6
Jack
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It has zero effect.

In a car, lightened engine rotating parts help by allowing the engine to change revs quickly. If you're accelerating a 3500 pound car, losing 20 pounds means nothing. With your jet boat, I expect the water you're pushing will be a similar significant resistance.

If you do all the math, you might indeed find that all this lightening at full throttle will make 0.1% of difference in acceleration. Once at full speed, and no longer accelerating, it makes exactly zero difference.
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