Going from 3 to 5 blade prop

QBhoy

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Hi
Pretty well up on the dynamics and black art of prop selection these days (or as much as one can be in this unpredictable minefield), but I'm seeking the experiences and general thoughts and even educated guesses of the forum.
I'm fortunate enough to have a really dialled in prop set up with minimum slip, but this year I'm hoping to get back into a bit of watersports, specifically wakeboarding and waterskiing.
Therefore I am looking for opinions or experienced based comments on the worth of a high 5 prop on the boat. For those not in the know, it's a 5 bladed prop specifically designed for watersports. I'm wondering how much top end I will loose and if I could ideally just use that all season as an all rounder, without too much compromise.
Any thoughts ? Would love to hear from users with sports boats or from anyone with an opinion.
Thanks.
 

wipe_out

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What issues are you having pulling water toys with the prop you already have?

On our previous boat which was a fairly heavy single engine sports cruiser we went from a 3 blade to a 4 blade for some extra traction on the water.. Dropped about 1-2kn top speed but was able to cruise better.. We didn't do any watersports so can't comment there..
 

julians

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I had the hi five prop on my old boat,it replaced a stainless steel 3 blade ,it worked really well for water sports, much quicker accleration,a lower minimum planing speed,and generally easier for the driver to hold a given speed. It cost about 3mph off the top end speed.

It was worthwhile imo for wakeboarding, i had one for about 5 years as a normal everyday prop.

However see my other post about the limitations of the alpha 1 drive
 
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MapisM

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I'm seeking the experiences and general thoughts and even educated guesses of the forum.
I can't offer 1st hand experience on the High5, because when I considered replacing the prop in my old lake toy, it was not an option for the Bravo XR shaft.
But according to hearsay - confirmed by julians post - it is indeed a great prop for watersport.

Otoh, since you are asking also for educated guesses, here's mine: from what I recall of your type/size of boat and her power, I would be surprised if you couldn't easily pull even a heavy skier with a slalom monoski (which is the worst case, when pulling anything), regardless of the prop.
And if that is the case, I for one surely would save the pretty substantial cost of the High5.
Slalom waterski is not for the fainthearted anyway, those who struggle to get out in a deepwater start with a boat like yours can as well stay on the dock...! :cool:
 

QBhoy

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Thanks again guys.
Mapism, I'm sure it wouldn't have a problem pulling deep starts, I was thinking more in the line of protecting the drive, as per other post. All be it probably a minimum measure ??
 

MapisM

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I was thinking more in the line of protecting the drive
Careful there. By fitting a prop with a higher grip upon WOT starts from standstill, you are actually putting MORE torque (hence stress) through the outdrive gear, not less.
 

TheOrs

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I had a HighFive 20P (small hub) on my Fletcher Arrowflyte/75HP Mercury. Acceleration was about the same as the previous 21P aluminium prop and top end was down from 47mph to about 42mph.
I replaced the HighFive with a 20P Laser II, modded to 19P. This gave me better acceleration than either of the two previous props and a top speed of about 45mph. An 18P Vengeance I tried gave even better acceleration but the engine was over-revving flat out.

The HighFive came with an early version of the 'Performance Vent System' (PVS). This features holes in front of the blades in order to allow the exhaust gases over the blades at idle. The idea is the blades grip less during initial acceleration, allowing the engine to spin up into it's peak power range. As the boat moves forward the water flow stops the gases escaping, the prop grips and the boat takes off. The Laser II came with the later version of PVS where you can swap out plastic plugs with different size holes (and hence gas flow). Mine came with the 'medium' plugs and worked quite well. We tried the prop with no plugs and the boat could not plane off; it just sat there 'wheel-spinning' :). I bought a bunch of various sized plugs but never got round to trying them because they are difficult to swap with the prop on the boat.

Even though the HighFive was slower on both acceleration and top end I was still loathe to swap it out because the grip it gave on cornering was phenomenal. The Laser II is almost as good and both are way better than the standard Quicksilver aluminium prop. With the HighFive I could throw the boat into a tight turn at pretty high speed and it would just grip and go round. You could feel your neck muscles tensing with the G-forces. Not much use really but great fun. The aluminium prop would just ventilate like crazy at the same speed, enough that the engine over-revved and you had to slow down.

All this is of course relating to a much smaller boat/engine than yours and although Mercury say the HighFive is suitable for 75HP and up I think it probably needs a big, torquey engine to come into it's own.
 

QBhoy

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Thanks the ors.
Useful insight.
Mapism you are ofcouse spot on with the grip the hi 5 will produce and likely action on the gearbox.
Mmm. Not sure whether to crack on with the water sports this year or not.
I suppose boats are there to be enjoyed and if we worried about every inch of our actions on them....we most likely wouldn't use them. Haha.
On another note, I managed to throw the boat in this afternoon (after just he mechanical servicing and no cleaning). Was a beautiful day out on the Loch and could be forgiven for thinking it was almost summer !
 

Freeloader

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Hi QBhoy,
You don't say what boat / engine / drive / propeller combination that you are currently running, so I hope that what follows is relevant to your circumstances. However, I have had a bit of experience with High-5 props on two boats, firstly a Monterey 180 Edge fitted with a 3.0L 135hp Mercruiser and a Maxum 1900 SR3 fitted with a 4.3L MPI 220hp Mercruiser.

The Monterey came (second-hand) with a 19" 3-blade aluminium prop but was under-propped and hugely over-revved to about 5,300rpm (WOT range 4,400-4,800rpm) doing about 40mph. Fitting a 21" High-5 prop brought the revs down to 4,800rpm and still achieved over 40mph. I did not use the aluminium prop enough to have any meaningful comparison with regard to acceleration but what was immediately apparent was the impressive smoothness of the High-5 and, as said above, the increased grip in turns.

The Maxum (bought new) came with a 19" Vensura 4-blade stainless prop, which seemed a good all-rounder, achieving 49.2mph at 4,800rpm (again, the recommended WOT range was 4,400-4,800rpm) and did 0-30mph in 7.5 seconds. Performance with the 21" High-5 was very similar but at lower revs, achieving 49.1mph at 4,650rpm and 0-30mph in 7.5 seconds. A 19" High-5 prop was noticeably faster out-of-the-hole but hit the rev limiter, achieving 48.5mph @ 5,000rpm and 0-30 in 7.0 seconds.

My experiences would suggest that the High-5 props run slightly higher revs than other props of the same pitch, so be careful in your selection - especially if you are already close to the rev-limit. Other than that, you will lose a bit of top speed but gain speed and acceleration in the low to mid-range. On the Loch, you have the opportunity to run at WOT over large areas, so it's your call as to whether a drop in top speed is worth the other benefits. However, in my view, the smoothness, grip in turns and acceleration for deep-water starts makes the High-5 the propeller of choice for me.

If you are looking for the Holy Grail (highest top speed and fastest acceleration), though, there is a hugely expensive alternative - an AeroStar twin-pitched prop. I tried one on the Maxum which had an effective 14" pitch until the boat came onto the plane and then dropped back to a 20" pitch up to WOT. Acceleration, by comparison, was brutal with 0-30mph in just 5.8 seconds but with an improved top end of 50.7mph at 4,850rpm. If you have got very deep pockets, nothing holds a candle to the AeroStar...
 

MapisM

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My experiences would suggest that the High-5 props run slightly higher revs than other props of the same pitch
Nope, it doesn't.
What you are implying with this statement is that the H5 slip is higher, but your numbers tell a different story.
Based on them, the only conclusion that can be drawn is that there was something wrong with the H5 19" used in your tests.
In fact, its slip is more than double compared to the H5 21" - something which, when comparing props of the same type and on the same boat, can't be justified just by production variances.
A 20 or even 30 percent plus/minus, yes. But 139%?!? No way.
 

Freeloader

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I perhaps did not word that correctly - I'm not implying that the slip is higher with a High-5 but that they seem to be of a lower pitch than their nominal sizing. For example, for any given revs across the range, the 19" High-5 gives lower speeds than the 19" Vensura and the High-5 tops out at higher revs - hence the apparent lower gearing for the same nominal pitch. Put another way, to maintain a set speed for skiing / wakeboarding etc, the High-5 will need more revs than the Vensura - hence my comment that the "High-5 props run slightly higher revs than other props of the same pitch".

In any case, it's not just me - other people have come to the same conclusion. There's not a lot in it but, as I say, if the OP is running close to the rev-limit already, it is certainly something to consider.
 

piratos

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Hi
Pretty well up on the dynamics and black art of prop selection these days (or as much as one can be in this unpredictable minefield), but I'm seeking the experiences and general thoughts and even educated guesses of the forum.
I'm fortunate enough to have a really dialled in prop set up with minimum slip, but this year I'm hoping to get back into a bit of watersports, specifically wakeboarding and waterskiing.
Therefore I am looking for opinions or experienced based comments on the worth of a high 5 prop on the boat. For those not in the know, it's a 5 bladed prop specifically designed for watersports. I'm wondering how much top end I will loose and if I could ideally just use that all season as an all rounder, without too much compromise.
Any thoughts ? Would love to hear from users with sports boats or from anyone with an opinion.
Thanks.

I have no updated experience with this as my Memory goes back to the time when the High5 was new to market. The prop came as an Option for heavy boats with gas engines, as the pitch they needed to fit max rpm and wot meant they had Problems to get on plane. The High5 lets the exhaust ventilate propblades increasing the slip during accelration.
If I remember right Merc suggested at that time to incrase the pitch with 1" if changing to High5 !

In a light boat like yours used for watersports it makes a lot more sence to have two props. By watersports highspeed is not nescessary (if I remember right competion Speed for Slalom is something ard 55 km/h and less for tricks skies or boards) - and aluprop with less pitch for deepwater starts makes more sence. With Mercs Proptools Change of prop is done in a Minute by the way.
If I remember right waterskiing behind a boat with a High5 was like being spanked under the feet, and the Aluprops were nothing like that.

One more thing I remember that when you put the gear in reverse it is like nothing happens - with the High 5 you Need more power !
One more issue - in watersports you repeatedly engange/disengange the gear - and with a heavy SS prop the Chunk from the gear is quite loud - less so and properly better for the gearbox.

Have a nice day
 

Freeloader

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I have no updated experience with this as my Memory goes back to the time when the High5 was new to market. The prop came as an Option for heavy boats with gas engines, as the pitch they needed to fit max rpm and wot meant they had Problems to get on plane. The High5 lets the exhaust ventilate propblades increasing the slip during accelration.
If I remember right Merc suggested at that time to incrase the pitch with 1" if changing to High5 !

In a light boat like yours used for watersports it makes a lot more sence to have two props. By watersports highspeed is not nescessary (if I remember right competion Speed for Slalom is something ard 55 km/h and less for tricks skies or boards) - and aluprop with less pitch for deepwater starts makes more sence. With Mercs Proptools Change of prop is done in a Minute by the way.
If I remember right waterskiing behind a boat with a High5 was like being spanked under the feet, and the Aluprops were nothing like that.

One more thing I remember that when you put the gear in reverse it is like nothing happens - with the High 5 you Need more power !
One more issue - in watersports you repeatedly engange/disengange the gear - and with a heavy SS prop the Chunk from the gear is quite loud - less so and properly better for the gearbox.

Have a nice day

Some good points made above... I have heard people complain that the High-5 is not so good in reverse, although, with a sterndrive boat, I never found it an issue. The 'clunk' into reverse, though, is definitely more pronounced - not really any more so than with any other stainless prop but certainly much more so than with a lightweight aluminium propeller.

It is interesting that you say that Mercury suggested increasing pitch by 1" if changing to a High-5 prop, as this is just what I was saying that I had noticed in my earlier post. It is generally accepted that, with sterndrive boats such as the Maxum, an increase / decrease in propeller pitch by 1" leads to a corresponding decrease / increase in revs at WOT of around 150-200rpm. Being that Mercury sells propellers sized in 2" increments, this generally leads to a 300-400rpm step at WOT with any change up or down in size. If we take the mid-point and say we expect approximately a 350rpm difference, changing up in size from the 19" Vensura to a 21" High-5 should drop the WOT revs from 4,800rpm to 4,450rpm. However, the actual revs were 200rpm higher at 4,650rpm. Similarly, changing from a 19" Vensura to a 19" High-5 should have left the revs unaltered but, in reality, the revs increased by 200rpm to nudge the rev-limiter at 5,000rpm.

Compared with each other, the 19" High-5 and the 21" High-5 behaved exactly as one would expect, with the 19" prop running exactly 350rpm higher than the 21" prop and achieving a slightly lower top speed. However, compared with the 19" Vensura, both High-5 props were running 200rpm faster than would have been expected - leading me to think that they are actually pitched around 1" lower than their nominal size. As the High-5 props compare so consistently, I have no reason to assume that either was faulty and, as the Vensura came fitted to the new boat and ran exactly to the performance specifications in the dealer's 'little black book', I have no reason to think that it was faulty either. From the above and considering Mercury's advice, it would therefore seem prudent to allow for a small increase in rpm if changing to a High-5.

With regard to the PVS plugs, you may be correct that they were aimed at boats with a heavy displacement that needed to encourage a lot of initial slip in the prop, so as to let the motor get higher up its power band and help get the boat onto the plane. The Maxum was certainly not underpowered and did not struggle to get onto the plane. Consequently, I did not notice any benefit from experimentation with the PVS plugs. With small vent holes, there was simply no noticeable difference but, with increasing size, the plugs simply encouraged a huge amount of slip with no apparent increase in acceleration. The props come with solid plugs and replacement blanks are readily available, so the easiest way to experiment is to simply drill out the blanks with ever larger holes.

From his opening comments, I took it that the OP was knowledgeable about propeller selection in general but was interested in comments regarding the High-5 in particular. In that regard, I hope all this has been helpful...!!!
 

MapisM

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I perhaps did not word that correctly - I'm not implying that the slip is higher with a High-5 but that they seem to be of a lower pitch than their nominal sizing.
Well, I never investigated the H5 in detail when I had my last outboard powered boat, because as I said I couldn't have used it in the Bravo XR drive.
But also the Bravo One which I used (4 blades s/s) is well known for being one inch shorter than its nominal pitch, so I have no reason to think that your conclusion is unrealistic, generally speaking.
Trouble is, according to your numbers there is a HUGE difference between the H5 19" and the H5 21" - the first having as I said a slip 139% higher than the latter.
Now, of course if I would do the same math using a 18" or 17" REAL pitch (as opposed to the 19" nominal), the slip would be much less, and this could lead to the conclusion you are drawing.
Otoh, the H5 21" has a much lower slip, calculated with your numbers and its nominal pitch - even lower than the 19" Vensura!
And that would lead to exactly the opposite conclusion, hence the comment in my previous post... :confused:
 

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Hi MapisM,
I'm probably missing something here but, from my calculations, the slip of the two High-5 props seem to be about the same? See the table below:

Prop Max Gearbox Potential Actual Prop
Pitch Revs Ratio mph mph Slip
19 5000 1.62 55.53 48.5 0.87
19 4800 1.62 53.31 49.2 0.92
21 4650 1.62 57.08 49.1 0.86

It is notable, though, that the 4-blade Vensura appears to suffer less slip. However, dropping 1" off the nominal sizings in the calculations produces a virtually even result:

Prop Max Gearbox Potential Actual Prop
Pitch Revs Ratio mph mph Slip
18 5000 1.62 52.61 48.5 0.92
19 4800 1.62 53.31 49.2 0.92
20 4650 1.62 54.36 49.1 0.90

As I say, I'm not quite sure how your calculations are derived - for prop slip I'm simply calculating the ratio between the theoretical top speed and the actual top speed.
 

Hambleite

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On our 2001 150hp Mercury Optimax we settled on 19p Laser 2 (3-blades), balanced, vent plugs in. Boat is a 6.5m Scorpion RIB.

Last year we bought a new 150hp Optimax and it never really performed as well as the previous unit (1000hrs). With this in mind, we experimented with various props with the aim of dropping 2inch of pitch to get the engine back in the powerband. So my comparisons aren’t exactly like for like.

17p Vensura (4-blades) – increase in 200rpm, as expected but lower speed
17p Revolution 4 (4-blades) – increase in 200rpm, as expected but lower top speed

We’ve also experimented with a 19p Vengeance prop (3-blades) with the previous engine – rather underwhelming – not fast, no real trim authority, lose grip / cavitate in turns.

The OP is right in that prop selection can be a bit of a black art but I’m happy to share any experience thus far.

Notes on 17p Rev4 vs 19p Laser2:
The 17p Rev4 is physically much bigger than the 19p Laser2. Gearbox would clunk when selecting gears. Sometimes it would be sufficient to stall the engine. The grip in turns was better. Boat has significantly more stern lift. Boat would plane at lower speeds and be happier at ‘just about planning speeds’ – 9-12 knots or so. Boat had really keen hole-shot - but that could be the drop in pitch as much as the increase in blade area.

In the end we fixed the problem with the new engine, got the revs back and she sings with the 19p Laser2. So much so, I might treat myself to 21p Laser 2. Anyone got one to try?

Overall my experiences would suggest that more blades mean:

More stern lift
Lower top speed
Lower WOT rpm
Better grip in turns
Potentially better hole-shot
Heavier propeller
More strain on drivetrain

As with any machine that only has ‘one gear’ – that gear will need the user to compromise somewhere!
 

QBhoy

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Guys,

This is brilliant stuff. Really appreciate the responses and the extra experiences given for different props on similar boats. It's exactly the kind of response I had hoped for.
Freeloader, thanks for the input. I have since read that going up a couple of inches is the way to go from a 3 blade stainless to a hi five. I'm most occasions too. Mapism, I can see freeloaders figures look realistic, do they not ?
Thinking if I go for the 21" I may not loose too much speed and perhaps 60mph is still achievable. It's a total pain having to change props all the time and by good practice, the nylock nut should probably be replaced each time too. Could end up expensive !
Piratos. You make a good point about the loader clunk with the stainless heavy prop.
Hamblite....this is superb stuff. Just the kind of details I have been looking for in other posts before now. In particular I was interested to hear about the rev 4. I too worried it's diameter was just too big.
I can't agree more with you about the laser. I've had one on a few boats now and although they are old hat now. I haven't seen or tried better for my particular boats. Works well currently and on a ring 18 with 200merc ob years ago. Make the boat fly.
I'm running a 19" with almost perfect results. <4 % slip if I have the calcs right. I just got rid of a 21". Although it was slightly quicker (not much), the boat wasn't as happy overall and elsewhere in the rev range where the boat is mostly used.
Keep the discussion going if we can !
Thanks
 
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