New prop advice

mrangry

mrangry

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I have recently acquired a 1992 Beneteau Oceanis 440 with 50hp Yanmar inboard shaft drive. She currently has a folding 2 bladed prop and she is a nightmare when trying to go astern, even in a flat calm. It is so bad that I dont normally enter the marina in daylight so cant be seen making several attempts to berth her. I initially thought it may just be my poor technique, but many others have also tried and commented on how unresponsive she is under power.

I am lifting her out the water soon and keen to change the prop to something more responsive. Has anyone got any words of wisdom to offer before i go spending a wedge as my knowledge on this is ....well zero to be honest.
 
I know very little about props, but mine came with a 3 blade feathering prop which you would be hard pressed to tell isn't fixed. Reverses exactly as you'd expect. I've sailed with a 2 blade folding prop and had similar experience to yours.
 
You'll probbaly get lots of different views on this but here is my experience. My yacht has a long fin keel and skeg underwater profile so it will differ from your Bene in terms of stern moving. When I bought her 14 years ago she had a feathering 3 blade prop which was supposed to make her easier going astern. Every year when she was on the hard I would carry out the manufacturers greasing requirements but despite this I didn't find it great. I also had the original fixed three blade that she was built with so I put that on as an experiment. That was 10 years ago and I haven't switched back. I know which way she will kick when going astern and have learnt how to live with that. The advantage of the fixed three blade is it gives better grip in the water and I don't have to worry about whether it has flipped around / unfolded. Some will say that I have lost put to knot because it doesn't fold or feather. I'd say that I don't notice that and I also sail in the Clyde / West Coast.

So my advice would be either (i) have good look at the proper next time she's on the hard and do whatever service the maker suggests. See if that makes any difference once you are back in the water or (ii) get a three blade fixed (it will be cheaper than any folding or feathering one by along way) and give that a try for a season or two.
 
Flexofold is owned by Yanmar so you might want to start there. Like @lustyd my yacht had a three blade folding prop (Volvo saildrive in that case). It was excellent in every way apart from the initial eye watering cost of it! Reversing was totally benign; and it had loads of power and bite.

It's important to match the prop to the engine. If you are also lacking drive ahead then it may be a incorrectly-sized aftermarket prop on your boat.
 
I wonder if the keel profile was affecting your prop Stooriefit? Mine feels identical to a fixed prop in both directions on a Jeanneau 36.2. I'm assuming you're confident yours wasn't broken too :)
 
We had a Kiwi 3 blade prop on the 40 HP version of your engine with sail drive
We could sail straight out of our berth at kip and manoeuvre in reverse

There are some caveats with the Kiwi

01672564456
Check with them on HP
Your gearbox may have a different ratio in reverse and ahead
They are best serviced every year not a big job but boat needs to be out the water
We usually managed to lift and scrub service SD and prop with a lift and hold over lunch

Two bladed folders are perhaps only loved by racing fanatics with elastic bands and even then it’s questionable ?
 
I can only speak from personal experience. I fitted a Volvo three blade folding prop many years ago. It is excellent in every way with plenty of bite in both ahead and astern. I take it off every year, dismantle and clean it, and grease it carefully on re-assembly. It still looks pretty new after this.

My one grouse is it eats anodes and the're not cheap. They don't really last a year, and I change them when the boat comes out on the Sea Lift for its half year scrub. Fortunately this is a quick and easy job.
 
mrangry said:
I have recently acquired a 1992 Beneteau Oceanis 440 with 50hp Yanmar inboard shaft drive. She currently has a folding 2 bladed prop and she is a nightmare when trying to go astern, even in a flat calm. It is so bad that I dont normally enter the marina in daylight so cant be seen making several attempts to berth her. I initially thought it may just be my poor technique, but many others have also tried and commented on how unresponsive she is under power.

I am lifting her out the water soon and keen to change the prop to something more responsive. Has anyone got any words of wisdom to offer before i go spending a wedge as my knowledge on this is ....well zero to be honest.
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I've always followed the advice that the ability of a prop to deliver thrust is related to its "disc" - how much of a plate the blades fill when looking up the shaft.
So 2 blades anything will not perform as 3 blades would. Vendors of folding blades always make satisfying claims for the output of their props but I have been sceptical, and cautious as to their reliability if fouled in nets etc.

Your engine sounds right for the size of boat, so is the diameter of your prop smaller than it should be on account of the shaft running too close to the hull to allow a larger dia prop? I'm told about 3 cm is the min clearance to allow without impairing prop performance / enduring drumming on the hull / generating excessive prop walk.

A good prop supplier will size you up for a standard 3 blade fixed. thereafter you can multiply your spend several fold with folding blades. BTW - my fixed doesn't cause me probs when sailing - I let it freewheel up to F5 then lock thereafter without loss of way. For the admitted marginal advantage of a folding prop at lower sailing speeds, I'm prepared to make a small sacrifice.

PWG
 
You might like to take a look at aMax Prop. I have a 3 bladed one on my Southerly 46RS, Yanmar 4JH4E about 45bhp.
All the advantages of a 3 bladed fixed prop' but I feathers to minimise drag, installed in 2007 and no problems, but it needs servicing every winter, and that's just pumping some grease through it, which takes less than 30 mins.
You can also adjust the pitch of the prop' to optimise the performance, and you can set a different pitch for forward and reverse, if you need to, to match the different ratios in the gearbox.
Dargow are the people to talk to, they have been going for years and know what they are doing.
 
Ian_Edwards said:
You might like to take a look at aMax Prop. I have a 3 bladed one on my Southerly 46RS, Yanmar 4JH4E about 45bhp.
All the advantages of a 3 bladed fixed prop' but I feathers to minimise drag, installed in 2007 and no problems, but it needs servicing every winter, and that's just pumping some grease through it, which takes less than 30 mins.
You can also adjust the pitch of the prop' to optimise the performance, and you can set a different pitch for forward and reverse, if you need to, to match the different ratios in the gearbox.
Dargow are the people to talk to, they have been going for years and know what they are doing.
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I contacted Darglow as I believe they are a UK manufacturing company and we now have so few, but I nearly fell over at the thought of spending just over 2k on a prop. I may just have to bite the bullet if that is the cost but just wanted to get the opinions and experiences of others before I do.
 
I installed a Brunton two bladed folding prop last August. Far better than the original at forward and reverse.

Before you go and spend your cash have a chat with the prop manufacture. There has to be a reason for poor handling in reverse.
 
mrangry said:
I contacted Darglow as I believe they are a UK manufacturing company and we now have so few, but I nearly fell over at the thought of spending just over 2k on a prop. I may just have to bite the bullet if that is the cost but just wanted to get the opinions and experiences of others before I do.
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We got a feather stream prop from Darglow for our old Sadler 29. It was excellent in both forwards and reverse, and very low drag when sailing. Highly recommended, and Darglow are a great company to deal with; they really know their stuff. Sadly not cheap though.

A fixed prop will give the same motoring experience, at a lot less cash, but if you like sailing, you won't like the drag.
 
Sandy said:
I installed a Brunton two bladed folding prop last August. Far better than the original at forward and reverse.

Before you go and spend your cash have a chat with the prop manufacture. There has to be a reason for poor handling in reverse.
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The tech from Darglow said that on my boat the shaft will spin a lot slower in astern than ahead and that a folder is therefore not suitable. The boat is due out of the water on 4 Jan so will take a good look to check it is opening and closing okay.
 
Scala said:
Flexofold is owned by Yanmar so you might want to start there. Like @lustyd my yacht had a three blade folding prop (Volvo saildrive in that case). It was excellent in every way apart from the initial eye watering cost of it! Reversing was totally benign; and it had loads of power and bite.

It's important to match the prop to the engine. If you are also lacking drive ahead then it may be a incorrectly-sized aftermarket prop on your boat.
Click to expand...

I would second the Flexofold recommendation. We also have the three blade and works very well.
 
dunedin said:
I would second the Flexofold recommendation. We also have the three blade and works very well.
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PS. At 44 feet, if the boat is a “keeper” you might want to fit a bow thruster sooner rather than later, to get most value from the investment. In proper tricky conditions steering also with the thruster increases your options in tight space.
 
I have had a succession of fin keel boats of different sizes with differing props and have yet to own one that is as difficult to steer in reverse as you describe. I tend to depend on the weight and momentum of the keel and imagine the hull with prop. and rudder as an extended appendage which can be used to direct where the keel goes. I do not think a change of propellor will solve your problem. I do presume that when in gear in reverse that steering will be compromised. how much depend on direction of the turn, so tend to give it a series of blasts to gain the necessary momentum and then put it in neutral when doing the actual manouvreing. Obviously the momentum needed is greater with stronger winds and tide but the keel seems happy to drag the hull with it in the direction or arc you set it on. After a while it becomes intuitive.
Sorry if this sounds a bit like teaching your granny to suck eggs.
 
The issue isn't just loss of steerage astern, it lack of any drive/power astern....its like stopping a super tanker.
 
A different ratio in reverse is due the gearbox manufacturers choice of gearing
You will probably have 3:1 in ahead but 2:1 in reverse resulting in the wrong diameter in one or other direction which there is nothing you can do to change it however you can alter the pitch with a variable pitch propeller exactly as Darglow have said

Is your problem directional control or lack of power?
Increasing the blades may help for control but having a prop with different pitch in reverse would also make a big difference I believe
 
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