Prop question

[printman71]

My local Yamaha dealer tried to explain why SHOs, don't have vented props, something about the SHO senses the unvented prop and advances the timing to aid in hole shot. I asked why Mercury 4 strokes still have vents. I was told Mercury makes horsepower with RPMs and the vented prop allows for the prop to spin up faster allowing adequate hole shot for a Mercury. Yamaha has more torque, so vent holes not needed.

Can someone better explain this to me or is this correct?

[bassfisher444]

Neither one comes with a prop, you install a prop based on what you need. Vents help improve hole shot if it is slow, if your hole shot is good then you don't need vents. That is the case no matter what brand motor you have.

[21XDC]

Neither one comes with a prop, you install a prop based on what you need. Vents help improve hole shot if it is slow, if your hole shot is good then you don't need vents. That is the case no matter what brand motor you have.

This is true. Many SHO owners get a better holeshot with vented props.

[bgibson]

This is true. Many SHO owners get a better holeshot with vented props.

Really? Wow, I find that interesting. I have a NON vented prop on my 250 SHO and can't imagine a faster/quicker holeshot...

[rammerjammer]

My local Yamaha dealer tried to explain why SHOs, don't have vented props, something about the SHO senses the unvented prop and advances the timing to aid in hole shot. I asked why Mercury 4 strokes still have vents. I was told Mercury makes horsepower with RPMs and the vented prop allows for the prop to spin up faster allowing adequate hole shot for a Mercury. Yamaha has more torque, so vent holes not needed.

Can someone better explain this to me or is this correct?

I had a conversation with a friend of mine this morning about this and he told me the exact same thing.

[bassfisher444]

Really? Wow, I find that interesting. I have a NON vented prop on my 250 SHO and can't imagine a faster/quicker holeshot...

Not all boats and boat setups are the same.

[21XDC]

Really? Wow, I find that interesting. I have a NON vented prop on my 250 SHO and can't imagine a faster/quicker holeshot...

[PSM207]

I have a 250 SHO spinning a Croxton Razor 4XL that has four PVS vents, all of which are open. The 4XL is very similar to the Bravo prop.
Ran it with all four closed, just two closed, then finally all open.

[ThomasD]

I run a vented T1 on my 250. Way faster holeshot then the non vented. No difference in mid range or top end.

[yam911]

Most interesting. On another forum they go on and on and on about how much more torque a two stroke has than a four stroke.

Along comes Yamaha and offers a vented VMAX propeller for their HPDI's, to help it to spool up, and then Yamaha offers a non vented VMAX propeller for the SHO model because of all of the torque that it produces.

Leaves one sorta confused.

[21XDC]

Taller pitch props like more venting. It’s like trying to peddle a bike in 10th gear up a hill. Venting acts like a lower gear, only on holeshot.

[PSM207]

Taller pitch props like more venting. It’s like trying to peddle a bike in 10th gear up a hill. Venting acts like a lower gear, only on holeshot.

I would lean towards this also.

[printman71]

Most interesting. On another forum they go on and on and on about how much more torque a two stroke has than a four stroke.

Along comes Yamaha and offers a vented VMAX propeller for their HPDI's, to help it to spool up, and then Yamaha offers a non vented VMAX propeller for the SHO model because of all of the torque that it produces.

Leaves one sorta confused.

So what is your professional opinion?
Is there a timing change (up or down) on acceleration?
Just curious.

[1ranger487vs]

Just a few years ago on this site people were saying you ran no vents on sho’s and vented on on 2 s. Well I ran a non vented on my 2 s just fine. No absolutes when it comes to prop setup. Every one is a little different

[21XDC]

The difference is 2 strokes "NEED" venting to spool up and get into the HP/Torque curve... 4 Stokes don't "NEED" venting, But can still benefit from rpms and controlled slip to achieve more thrust.

[yam911]

My opinion is that I don't know what to make of 99.999% of the stuff that I read on the innerweb.

[printman71]

My opinion is that I don't know what to make of 99.999% of the stuff that I read on the innerweb.

Right there with you!

[cwilt]

All in all...run what puts a smile on your face. Figure out your best hole shot and your best top end without lugging your motor and enjoy.

I have a 2 stroke and dont need vents my motor is full of torque.

[21XDC]

All in all...run what puts a smile on your face. Figure out your best hole shot and your best top end without lugging your motor and enjoy.

I have a 2 stroke and dont need vents my motor is full of torque.

That is because you have a 2.0:1 gear ratio. And it probably would do even better vented to 3500-4000 on holeshot.

[NHRG]

So a lot of SHO owners run a T1 of T2 unvented. What would 21XDC run if he owned a SHO?