Prop for a 15hp 2 stroke yam (prob early to mid 1990s)

[dgpw]

I am after a 4 blade or three blade with more cupping / lower pitch as the boat is heavy and there is a small amount of ventilation and possibly some cavertation. Any one know where I can get one this small?

[Fenlander]

By small do you mean low pitch and is it for a displacement boat or SIB that planes?

On Ebay alone there are loads of props for your motor from the £40 Chinese types to Solas brand around £60 and then Yamaha OE usually £85 or so.

If by chance it was a displacement boat this is a bargain...

https://www.ebay.co.uk/itm/Yamaha-Ge...gAAOSwiqFaT61N

Even if not worth messaging that seller as he mostly has several props for your motor.

[xpertski]

I might have one that fits the 15hp, will check. It’s a genuine Yam one which hasn’t been used

[Locozodiac]

You need to fix firstly the boat/motor aeration, ventilation issue before venturing blindy swaping other prop. A les prop pitch will ventilate worse as will up the wot rpm more than before.

If pushing a heavy boat prop should not ventilate unles the motor sits way up on transom. Will need to go for a OEM Yam prop for motor to rev at its full wot rpm range factory stated for that motor once the aeration issue has been fixed.

What need to do is : inflate boat well, set trim to 90 deg, distribute deck load evenly, go for a wot spin on flat calm water cond if possible, pull head out middle transom and check at which lower leg height is water flow passing by at speed/plane.

If it's passing around the lower AC plate, there's your prop aeration issue, need to lower the motor for flow to skim right under the upper plate which is the hotspot height for any given motor brand with large plates distance as found in the lower leg area.

This is the ideal lower leg height for top boating, along excellent prop thrust at all water cond, that's from flat calm to choppy/windy ones, not extremely though.

http://www.youtube.com/watch?v=oBeZj...ature=youtu.be

Happy Boating

[Fenlander]

Just an extra bit of info...

In the 15hp size (and possibly for other hp motors) Yamaha had two prop ranges... one the standard and the other often described as a cupped or high thrust type.

In the image below are two of my props for our 15hp 2-stroke.. the right hand one is the standard with the more swept style blades and a part number starting 683 of the J type... and on the left is the high thrust type with more petal shape blades and part number starting 63V having the J1 designation.

The standard type is Yamaha OE and the higher thrust a Polaris aftermarket but that doesn't affect the info above.

[dgpw]

Originally Posted by Fenlander

By small do you mean low pitch and is it for a displacement boat or SIB that planes?

On Ebay alone there are loads of props for your motor from the £40 Chinese types to Solas brand around £60 and then Yamaha OE usually £85 or so.

If by chance it was a displacement boat this is a bargain...

https://www.ebay.co.uk/itm/Yamaha-Ge...gAAOSwiqFaT61N

Even if not worth messaging that seller as he mostly has several props for your motor.

It is on a 13 ft pioneer so planing hull but heavy and won’t quite plane with this engine. It should be a long shaft but the engine is short shaft (I already have it and it fits in the car) to be honest the ventilation is only at wot when turning so not an issue. Cupping on the prop would stop this but I am finding it hard to find a 4 blade or a prop with cupping that is so small.

[Fenlander]

Oh a shaft mismatch is always going to add issues to a normal optimised setup... but looking the Pioneer 13ft is spec'd for a short shaft... well the current model is.

Again I'd ask what you mean by a small prop... and what is the current pitch?

[dgpw]

Originally Posted by Fenlander

Oh a shaft mismatch is always going to add issues to a normal optimised setup... but looking the Pioneer 13ft is spec'd for a short shaft... well the current model is.

Again I'd ask what you mean by a small prop... and what is the current pitch?

:-) thank you, I mean it is much smaller than the one on my 225hp or my zapcat where I have hundreds of options :-) the pioneer 13 I have is an early one and is spected for a long shaft but actually the cav plate is only about 1 inch to high so it is only when semi planning that there is a problem, and it only just manages to do that with the 15hp

[dgpw]

Originally Posted by Fenlander

Just an extra bit of info...



In the 15hp size (and possibly for other hp motors) Yamaha had two prop ranges... one the standard and the other often described as a cupped or high thrust type.



In the image below are two of my props for our 15hp 2-stroke.. the right hand one is the standard with the more swept style blades and a part number starting 683 of the J type... and on the left is the high thrust type with more petal shape blades and part number starting 63V having the J1 designation.



The standard type is Yamaha OE and the higher thrust a Polaris aftermarket but that doesn't affect the info above.

That is very usefully it is the high thrust I need, do you know where I can get one?

[Fenlander]

Many sellers do not accurately describe these Yamaha 15hp props so you need to be very sure they are going to send what you want.

As I said above the higher thrust type seems to usually have a J1 designation but often only if an OE... the aftermarket types usually just have the part number forgetting the J or J1... again as mentioned above as far as I've experienced part number starts with a 63V for the higher thrust type.

Here is just an example...

This visually looks a high thrust type and the part number starting 63V looks right... but then the designation is given as a J which from those I've bought would be a standard thrust type. The link is to an 8" pitch aftermarket... I'm sure you know it's important you check the existing pitch before you can start working out any changes.

These motors usually run a 9" or 9.75" pitch on a SIB so I'm guessing you need to drop pitch??

https://www.ebay.co.uk/itm/Yamaha-Ou...sAAOSwbDZaw1ys

[dgpw]

Originally Posted by dgpw

That is very usefully it is the high thrust I need, do you know where I can get one?

Better still would be a 4 blade with cupping if they exist :-)

[Fenlander]

If you are failing to plane surely you first need to consider what your existing pitch is and depending on that then consider pitching down??

[Locozodiac]

Need to buy an induction tach, install it properly and tach the prop you've gone after at max throttle to check its max wot rpm achieved to know if inside its factory stated wot rpm range. If way under will be lugging extremely the motor which is No Bueno..

Unless it's an old Yam model, there should be a varied prop selection to choose from regarding newer 15 HP Yam models..

Happy Boating

[dgpw]

Originally Posted by Fenlander

Many sellers do not accurately describe these Yamaha 15hp props so you need to be very sure they are going to send what you want.

As I said above the higher thrust type seems to usually have a J1 designation but often only if an OE... the aftermarket types usually just have the part number forgetting the J or J1... again as mentioned above as far as I've experienced part number starts with a 63V for the higher thrust type.

Here is just an example...

This visually looks a high thrust type and the part number starting 63V looks right... but then the designation is given as a J which from those I've bought would be a standard thrust type. The link is to an 8" pitch aftermarket... I'm sure you know it's important you check the existing pitch before you can start working out any changes.

These motors usually run a 9" or 9.75" pitch on a SIB so I'm guessing you need to drop pitch??

https://www.ebay.co.uk/itm/Yamaha-Ou...sAAOSwbDZaw1ys

Thank you, very useful