4 bladed props?

[Adam F]

Anyone running or tried a 4 bladed prop?

 

I read that they can offer an advantage on heavy offshore boats spending a lot of time cruising?

 

Are they worth looking into?

[great white]

Yes mate 

 

I have one, in front of the three bladed one that runs in the other direction.

Bloody clever these duo props.

 

Seriously I would discuss with Volvo mate to see what they suggest. I do not know how well they work on legs.

 

On shaft drives they work very well to eliminate vibration and improve performance.

 

Charlie

[sparky]

Mines 4 bladed Adam..............and it has a lovely singing voice !!!!!!!!!!!!!  

The accelaration seems better than 3 bladed props on same boats, but the 3 bladed props seem to give a higher speed .

 

Mick

[Maverick Martin]

Adam

 

AWOL has a 4 bladed prop. Last prop I was running was a 14.25" dia by 21deg 3 blade we now have a 15.25" by 18deg pitch 4 blade prop

The main benefit for me is the ability to cruise at lower speed (yeh yeh go on you lot take the pee  ) without falling off the plane so easily.  Hole shot is much more aggresive and for me top end is higher though I would say this is because my old prop was carp. I do though suffer from more prop torque so need to use more trim tab or move some kit around.  Would I go back to three blades? definately not with this boat.

 

More information on my repropping here: http://www.worldseafishing.com/forums/boat-owning-equipment-maintenance/214044-old-chestnut-prop-selection.html

 

 

Martin

[Adam F]

Thats great Martin. I think for the type of fishing us larger boats do, the holy grail is a more economical cruise. Is there a really noticable difference, not just a slight one? When I think to what we do on JV 80% of the time, it's running around against the tide up and down drifts with alot of gear and anglers onboard, so a quicker hole shot and more economical cruise makes sense.

 

Is your Stainless Steel or is there a Ali option? Did it take much messing around with sizes to get it right?

 

Maybe I'll drop into Prop Sol on the way to work on Fri morning.

[Maverick Martin]

Hole shot for me was very noticeably better exactly as described in the wsf thread.  The ability to keep on the plane at lower speed without having to keep constantly playing with the throttle is also a boon

 

My prop is stainless steel I never even considered an ally option.  Tom at prop sols got the spec almost spot on first time although I might get the prop repitched to 17" as when the boat is fully loaded can only get 4200rpm instead of the 4500rpm.  Re pitching by 1" will give us even better hole shot and better cruising in the rough stuff

 

Martin

[Adam F]

Popped into Prop Sol on Friday - very helpful.

 

It's £480 plus VAT for a 14.25" prop for JV, in S/S - but they reckon it will show a big advtange - esp on the wide gear casing that the SX Ourdrive has.

 

Think I'll get one on order and tested ready for Alderney.

[great white]

Does that mean we will have that little race again this year Adam

 

Lol

[Maverick Martin]

Good luck Adam hope you achieve as good a result as I did

[great white]

Good luck Adam hope you achieve as good a result as I did

Are we talking about the prop, or boat racing

 

You know we do not race Awol Martin, its depressing to lose that often  

[Adam F]

I opened her up on Sat to check WOT and whilst all the extra kit we seems to accumulate had dropped the top speed we got when launched she will still touch 30 knots at 3600rpm.... I never, ever use it though - if it's flat and I'm in a rush I might run at 3000rpm which gives just over 20 knots. Most of the time I sit at 2600-2800 and 16-18 knots.

 

If I can improve on the hole shot and get on the plane and cruise more efficeintly it will be worth it. The worst conditions for me are like we had coming back over the channel a few years ago in that 5-6 westerly where I was on and off the plane and throttle around 12-14 knots... it just ate the fuel. I used about 75% more than I would have on a usual channel crossing.

[niggle]

I'm interested to see you're results

I'm happy with my performance but if I can gain something it might be worth the hassle of a few lifts.

Now she's nice and clean I get 22/24 knots cruising and 30/34 knots wot

But I have to run with my tabs right down to sit on plane nicely.

Nige

[great white]

Nice to read that the 4 blade makes a big improvement and is therefore a good investment.

 

That is the reason I went for the Duo Prop during build.

 

Its never been about the WOT, although it is fun to have a blast at 30 knots occasionally.

Especially when sports boats wave at the fishingboat as they go by, then look a bit shocked with our acceleration and speed.    

 

Its sustained cruising at reasonable consumption that is our main concern.

 

If we can not plane it affects our fuel consumption , but not as badly as Adam describes.

 

Charlie

[Steve S]

4 blade props are better than 3 blade props for hole shot punch and mid range efficiency, but worse for top end speed. I think for us fishermen they are spot on.

 

Also very important is getting the boat to run to maximum revs, it sounds simple enough however you need to consider loading and for boats on a mooring the fouling build up over the season.

 

A boat pulling max revs with a clean bottom and lightly loaded with be pulling well below that at the end of the season and when loaded up, not a good thing to do, it bogs the engine and some engine get real unhappy about running overloaded. I would suggest aim to permit max revs under your max normal load and about 3 months fouling.

 

My old MF 805 used to over rev by 350 rpm (4250) early in the season on my max normal loading of the boat (4 people, full tanks). The next year I got the prop repitched so that it still over reved by 150 rpm early season but was about on max (3900) by July and down to 3700 in Dec. Max revs for a volvo tamd41 is given as 3700 to 3900. The improvement for me was over a knot at normal cruising revs and a corresponding fuel saving.

[Adam F]

Went to Prop Sol today to order the prop up, but he wasn't confident of the improvement I'd see? He said he was 80% sure but spending £600 on a prop that I couldn't change or return was too much of a risk.

 

Martin, shame yours wouldn't fit my leg as he recommended a 15.25x18 for me.

[Rob]

Seems crazy that the manufacturers don't have loan ones / exchange systems. A £75 prop is one thing....multiple £100's is another!

[Rob]

How much are they in the US Adam? Maybe someone you know is going there soon! ;o)

[Adam F]

About £150-£200 in the US... It's the postage to the Uk which kills it. If you are going that could be an option?

[Rob]

Let's talk. I'm off in June, how big will it be and heavy?

[Sinbad]

14.25" prop

   

 

+trim tabs ???

 

At least you can pack the box with braid and other goodies!!

[Maverick Martin]

Adam my prop is on a bravo 1 leg do these not fit VP?  If they do you are more than welcome to try it

[Adam F]

Hi martin,

 

The prop you have is what we reckon would work for me - I dont think the fitting is the same though. If it was a Mercruiser prop they do a hub kit - but not for the Powertech props.

 

The Volvo is 19 spline.

[Adam F]

Wow - I am confused!

 

My current prop is 14.25x21"

 

Prop Sol advised to go down a size in pitch to 19" and then up in diameter to 15"

 

Ive just spoken to Steel Developments: http://www.steeldevelopments.net/125-300-hp-propellers-approx-13-to-16-diameter-with-4-3-4-gearcase-1/4-blade-stainless-steel-hr4-e-series.html

 

They advised that if I am getting the right revs currently to stick with what I have - and they advised a 14.25x19. Thier prop option is half the price of the one Prop Sol offered too. They will re-pitch the prop for £30 if it is wrong.

 

From what Ive read from trawling the web this morning I'm convinced that 4 blades is the way to go, it's just which one and how much to pay....

[Steve S]

If they will repitch for just £30 then you have your insurance policy in case their recommendation doesn't work out quite right, a pretty good offer.

 

There are lots of opinions about pitch v diameter ask 10 people and you will get a broad spread of answers, I'm not going to add to it here by pitching in (sorry) with mine.  Sounds like you have a choice to do either, many boats don't have much option on the diameter due to other parts of the boats getting in the way of efficient operation.

 

Remember to take account of your load (people and equipment) on the boat and fouling as I mentioned in an earlier post in this thread when doing your full power run.

 

Steve

[great white]

Sounds better, with the offer of a re pitching option at least you get a bit of room for error.

 

The trials should be done with the boat loaded to normal, tanks full and some no of persons onboard. If you need an extra man for a sea trial Sam or I  may be available

 

The prop suppliers really should know the differance needed to get what you want from the prop change,

I always thought that it is the initial prop choice of a bespoke boat that was difficult.

 

Charlie