How high can you safely spin them?

[Bullet 20cc]

I haven't had this big OX 250 long enough to cut the fun limiter yet...still working on perfecting set-up. But it will be getting cut when I get the two gelled together...just a click or 2 away now. I was a 2.5 Merc guy previously and used to spin those to the moon!

I've been doing alot of reading about it but would like to get you guy's opinions and/or experiences with max rpm on the 3.1...without having to buy a new cowling. Most I've read/seen so far is 6700...

[ClarkBird]

6700 is awful tight. I was told 5800 should be about it.

[Bullet 20cc]

I agree with 6700 being up there for a large (3.0+) displacement motor. But the Merc 3.2 'stroker' 300xs factory rev limits at 6400 and will continue to make power all the way to it. Paul Nichols even cuts the factory rev limiter on the Yamaha 3.1 and runs it up to 6450...turning very large wheels too 32/33 pitches! I don't think the 3.1 is even breaking a sweat at 5800. Not trying to offend any Merc owners cuz I have always been one myself. But this Yamaha seems to be engineered to a higher degree than any Mercs I've had. So if the biggest Mercs are turning 6400...seems logical that the big Yamaha could at least spin that with even some more potential above that.

Reason why I'm asking is because limits on prop pitch and lower unit gearing can be maxed out fairly easily on the Yamaha 3.1...especially if it has been Hydrotec'd. Sure a 34 pitch can be ran to bring rpm's back in line with factory specs...but that's bordering ridiculous. This leaves only rpms to be increased to get more. Just how much more rpm can safely be had? Already spin a 30 pitch on the rev limiter (6150) without even being matted...there's more pedal to be had. I have read of the 3.1's being spun to 6700 regularly to with no problem...looking for somebody to confirm that?

[ClarkBird]

I would call Wayne at Hyrdotec for his insight.

[Bullet 20cc]

Good call Clark...If anybody would know it has to be those guys.

[HaulinBass]

Was told by HT that they can be spun >6150 with the wire cut and still produce hp.

[StrokerSmoker]

The 3.1 s will go to 6700 but its really not much use 6400 is about peak hp

[Bullet 20cc]

The 3.1 s will go to 6700 but its really not much use 6400 is about peak hp

Thank you StrokerSmoker! Exactly what I needed...sweet Stroker btw! Looks awesome with the Hammer/Sporty back there!

[ClarkBird]

The 3.1 s will go to 6700 but its really not much use 6400 is about peak hp

Is that with different heads or just the rev limit cut? Mine is bone stock and I like to run it about 4900-5k cruising. Seems I can spin it a bit tighter if that's the case.

[StrokerSmoker]

factory is 6150 cut the rev limiter and they will turn some more rpms..,,,I prop them as close to the limiter as possible....lugging a 2 stroke isn't good

[harleyrs]

Which wire do you cut, is it the gray jumper on ecu.

[ClarkBird]

Which wire do you cut, is it the gray jumper on ecu.

Yessir

[harleyrs]

Thanks Clark, 5800 rpm is all mine will turn, I have the Phase III kit in the OX66 250HP.

[ClarkBird]

What boat and prop?

[harleyrs]

Skeeter ZX250 tried 27T1 and 26 Tempest Plus

[ClarkBird]

If it won’t pull a 26 drop down one more. Ought to scream with the ph3 kit.