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What's the Max RPM my F300 should be turning?

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What's the Max RPM my F300 should be turning?

Old 04-22-2018, 09:34 AM
  #1  
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Default What's the Max RPM my F300 should be turning?

2016 F300XCA on a Blackjack 256.

When I got it, I'm thinking it was maxing out at about 5400 rpm, about 55 mph. Since then, I've added a T-top, not sure if that makes any difference.

Now noticing that I'm maxing out at about 5200-5300 rpm, and closer to 50 mph, granted there was some wind last trip.

I'm okay with the mph reduction, but wondering if I should be gettting more rpm/mph out of it.

Running a Yamaha Saltwater Series II, 21-T, 15 prop.

The published "Full throttle range" is 5000-6000. The hp rating says 300 at 5500 rpm.
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Old 04-22-2018, 10:44 AM
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You are overpropped. You should be turning as close to 6000rpm at WOT or these engines have a tendency to make oil.

If you run overpropped for too long you might be out of the window for fixing it by getting proper pitched props and running it hard at WOT for a few hours.
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Old 04-22-2018, 01:18 PM
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Originally Posted by 565 View Post
You are overpropped. You should be turning as close to 6000rpm at WOT or these engines have a tendency to make oil.

If you run overpropped for too long you might be out of the window for fixing it by getting proper pitched props and running it hard at WOT for a few hours.
This ^^^^

You should be very near the upper end of that RPM range at WOT with a moderately loaded boat, with the engine(s) trimmed up to just below ventilating. Trim up a bit, listen, watch speed and RPM for increases. Trim up again, etc, until no gain and the sound changes. Then trim down a bit and you are there.
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Old 04-22-2018, 06:18 PM
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For some reason a t-top or hard top really slows a BJ down. Everybody I have seen on here has lost 4 to 5 mph atleast on the top end.

That 300 needs to be no less than 5800 with a decent load with motor trimmed. Making oil might be a problem if you don't get it propped right.

The SWS II 19 pitch should get you very close.
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