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Stupid question but are Yamaha 4.2L 300s underrated??

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Stupid question but are Yamaha 4.2L 300s underrated??

Old 06-06-2019, 01:56 PM
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Default Stupid question but are Yamaha 4.2L 300s underrated??

Sorry for the dumb question. A couple of capts, at different times and different places, told me their Yamaha rep said the 4.2L 300s are underrated and actually put out closer to 350 to 375 HP at the top end of their power band. I know that some auto manufacturers, like Porsche, underrate performance and power values. Is this also the case with Yamaha and other marine motor manufacturers? Nothing on the Yamaha site supports these comments and I've seen the power band report on this motor showing no more than 300 HP. So I figured someone here would have info on this rumor.
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Old 06-06-2019, 02:20 PM
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A Rep would never lie.
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Old 06-06-2019, 02:28 PM
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ummmmmmmm no!
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Old 06-06-2019, 02:37 PM
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A rep will not have a clue. All that a rep here in the US knows is what Yamaha Japan is telling him.

Yamaha Japan does not disclose that type of information.

Try and get a HP or torque curve from Yamaha or Mercury.
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Old 06-06-2019, 02:52 PM
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False, it's well known that only Mercury engines put out more HP than their stickers say.......
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Old 06-06-2019, 05:58 PM
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A few years ago, not long after the 4.2's first came out, there was a school of thought that the F250 was more like about 265hp and the 300 was about 290. I have nothing solid to support this, only that a couple of reputable dealers I know were steering customers to the 250 because the extra coin for the 300 just wasn't worth it for about 25hp gain.
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Old 06-06-2019, 06:13 PM
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Originally Posted by OBX351 View Post
Sorry for the dumb question. A couple of capts, at different times and different places, told me their Yamaha rep said the 4.2L 300s are underrated and actually put out closer to 350 to 375 HP
No such thing as dumb questions, just sales reps full of BS.
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Last edited by BiloxiGuy; 06-06-2019 at 06:18 PM.
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Old 06-06-2019, 07:12 PM
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F 300= a great reliable motor with a proven track record with great fuel economy. That being said, My Ox66 can keep up with My same hull with older F250s and the newer F300s. I think the heavier 4 strokes just weigh down the stern to much. Again, just my hull and my experience. I just cant pass the fuel dock.
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Old 06-06-2019, 10:46 PM
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Absolutely not... they are overrated. 221 kw= 296 HP
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Old 06-06-2019, 11:56 PM
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Rodngun762 has the real truth. The rep did not just stretch the truth, but claiming 375 out of a 300, he absolutely destroyed it.
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Old 06-07-2019, 01:00 AM
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A commercial cat owned by a friend swapped out a pair of f250s for f300s on the 8m cat.

Picked up 3kn up top burning 10% more fuel.

Side note. When it was originally bought, the boat had Suzuki 300s. Then he fitted the F250 4.2s. That combo was 1-2kn slower than the Suzukis.... So the Suzuki combo wasnt exactly night and day compared to the yams.

250/300 on this particular heavy cat hull makes little difference.
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Old 06-07-2019, 03:19 AM
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The rep was a fool. Anyone that has been on a boat with an f300 or f300’s knows that at best the engine is 300hp and honestly they are probably missing a few ponies off that 300hp sticker. I too would believe closer to 290.
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Old 06-07-2019, 03:24 AM
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Originally Posted by EMC Pursuit View Post
F 300= a great reliable motor with a proven track record with great fuel economy. That being said, My Ox66 can keep up with My same hull with older F250s and the newer F300s. I think the heavier 4 strokes just weigh down the stern to much. Again, just my hull and my experience. I just cant pass the fuel dock.
I know we have talked about my repowering with F250's in the past. The weight difference from the OX66's has had no effect on capacity or performance. In fact the boat sits the same at the dock as it did with the two strokes on her.

I too defended my OX66's till the day I hung the 250's on the back. I loved my reliable, easy to work on, smelly, shaky and noisy two strokes.

You know what.....I love my 4 strokes even more! The Pursuit is a totally different boat with them on the back. Cmon over to the no smoke side, you will not regret it!
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Old 06-07-2019, 04:11 AM
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Winter, spring, summer, fall, same thread topic, same posters, different OP.
Yet the F300/F290/F296/F310/F370 still purrs along.
Don't ya'll have fish to catch somewhere?
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Old 06-07-2019, 05:19 AM
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Originally Posted by BiloxiGuy View Post
No such thing as dumb questions, just sales reps full of BS.
You have been here for a while. Pay attention. There are many many stupid questions that get posed here.

Is this place the exception to the "no such thing as a stupid question" rule?
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Old 06-07-2019, 05:21 AM
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Originally Posted by Rodngun762 View Post
Absolutely not... they are overrated. 221 kw= 296 HP
What does this have to do with the output of outboard motors that out are in the field?
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Old 06-07-2019, 05:22 AM
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Originally Posted by Parker Yacht View Post
Winter, spring, summer, fall, same thread topic, same posters, different OP.
Yet the F300/F290/F296/F310/F370 still purrs along.
Don't ya'll have fish to catch somewhere?
There is no present or future here on THT.
There is only the past. Being repeated over and over again.
Now.
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Old 06-07-2019, 05:45 AM
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Think logically...if it put out 375, they would call it a 375. In the current war for more HP, why would they underrate the motor?
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