Duo-prop size - Sealine S34

Greg2

Greg2

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Trialled an S34 last week on the river and the KAD32s pulled around 3,300 rpm max and she did around 27knot SOG (about 24 through the water but not sure how well calibrated the log is). KAD32s should pull 3,700 to 3,900 - but she is making the right speed, or seems to be. She has A4 props fitted.

Feedback from S34 owners with KAD32s indicates that they have A4s but it has been suggested maybe we need A5.

Anyone know what the right props are for this boat please?
 
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Original props would have been A4.

You should be getting somewhere North of 3700rpm on there, not 3300rpm.

Changing to A5 is only going to make things worse.
 
FlowerPower said:
Original props would have been A4.

You should be getting somewhere North of 3700rpm on there, not 3300rpm.

Changing to A5 is only going to make things worse.
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Thanks, that is what I thought. If we did get a genuine 27 knots then boat is making expected speed but tachos not showing what RPM we would expect.
 
Start from basics , engines and drives don’t have props allocated to them.
weight of boat hull types etc?
The most important factors, how clean is the hull and how much crap (weight) on board?
 
Bandit said:
Start from basics , engines and drives don’t have props allocated to them.
weight of boat hull types etc?
The most important factors, how clean is the hull and how much crap (weight) on board?
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Fair comment. Have been working on the basis that the S34 was made in some numbers and there is a lot of experience out there and everyone is saying A4s. That said local engineers software, which appears to be working on engines, drives and boat characteristics, is saying A5

Boat hull clean and empty of kit - fuel tanks fairly full and water virtually empty.
 
If you are changing props be careful. I wanted to replace my A7's on my Targa 33 but VP don't make A's any more so had to go to the new improved J prop.

All the numbers etc were done and a J7 was due to be a direct replacement...well as son as i put a J prop on i lost 10% of speed.

So do you number carefully and buy some old stock A's if you can find them...i wish i did!!!!
 
I can never understand why people want to change the prop sizes on a mass produced boat like this. Unless there is overwhelming opinion that the original prop size was wrong the issue has to be something else (fouling, turbos, fuel, etc).
 
Sailorsam101 said:
If you are changing props be careful. I wanted to replace my A7's on my Targa 33 but VP don't make A's any more so had to go to the new improved J prop.

All the numbers etc were done and a J7 was due to be a direct replacement...well as son as i put a J prop on i lost 10% of speed.

So do you number carefully and buy some old stock A's if you can find them...i wish i did!!!!
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Interesting, I have heard that A series are a direct swap i.e. A4 to J4 and B series are one up i.e. B5 to J6. Didn’t seem to work like that for you though. Thanks for the heads up.
 
I'm watching with interest on this as just about to survey a S34 that needs new props. Pre survey sea trial showed 3400 max on one engine and 3000 on another with 21kts. Now the reason for the difference was one half of the duo props had fallen away on the trial and all 4 are being replaced prior to survey.

I have no idea what they are fitting size wise but they are J series and not A. I will check they are 4's and not 5's

On my current S28 we had new props due to an 'incident with a rock'. Previous A props before the rock problem returned 37-38 kts flat out and 3900 rpm. The new J props of the supposedly same size/pitch return 33-34kts and 3800rpm

So as above I am losing about 10% currently. This isnt an issue on a 28 as there is plenty of power and speed but I am now a bit concerned that the S34 will struggle to hit 30 with J's fitted.
 
Bbroomlea said:
I'm watching with interest on this as just about to survey a S34 that needs new props. Pre survey sea trial showed 3400 max on one engine and 3000 on another with 21kts. Now the reason for the difference was one half of the duo props had fallen away on the trial and all 4 are being replaced prior to survey.

I have no idea what they are fitting size wise but they are J series and not A. I will check they are 4's and not 5's

On my current S28 we had new props due to an 'incident with a rock'. Previous A props before the rock problem returned 37-38 kts flat out and 3900 rpm. The new J props of the supposedly same size/pitch return 33-34kts and 3800rpm

So as above I am losing about 10% currently. This isnt an issue on a 28 as there is plenty of power and speed but I am now a bit concerned that the S34 will struggle to hit 30 with J's fitted.
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Does the boat have KAD32s? From what I have been able to glean they should pull around 3,750 and 27 knots at WOT with A4 props.
 
Yes it has KAD32's, but with fairly high hours. As long as it pulls WOT at 3800 ish and around 27-30kts range I will be happy -especially given the fuel tanks are only 1/4 full. Broker is well aware that it needs to get to full revs on a survey sea trial so hopefully a new set of props will help - I just hope they are the right ones!
 
Bbroomlea said:
Yes it has KAD32's, but with fairly high hours. As long as it pulls WOT at 3800 ish and around 27-30kts range I will be happy -especially given the fuel tanks are only 1/4 full. Broker is well aware that it needs to get to full revs on a survey sea trial so hopefully a new set of props will help - I just hope they are the right ones!
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I would go with J5 on an S34.
The sizes are not quite equivalent.
 
You can still get A / B duoprops. BS.Pro make them and they are highly rated compared to other copies according to a number of prop specialists I spoke to in my own search for the best prop. You can order them from Keypart.co.uk
 
Bbroomlea said:
Yes it has KAD32's, but with fairly high hours. As long as it pulls WOT at 3800 ish and around 27-30kts range I will be happy -especially given the fuel tanks are only 1/4 full. Broker is well aware that it needs to get to full revs on a survey sea trial so hopefully a new set of props will help - I just hope they are the right ones!
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Perhaps we can keep updated on here as I will be interested to see how you get on, particularly with the J series and whether you go for 4 or 5. An owner of 10 years told me that with the KAD32 on A4 it was 3,750 rpm and 27.1 knots absolute flat out.
 
For those looking for new propellers I too can recommend Keypart. Just ordered a new set of G7s and they were well under the price offered by others without any negotiation.
 
petem said:
1999 brochure speed for an S34 with KAD32's was 30/32 knots so it's not achieving top speed.
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Greg2 said:
Thanks Pete, that is helpful.
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Having pondered this overnight, 1999 was not long after the KAD32 was launched and I wonder if the brochure speeds were proven when it went to press. A later brochure might show a lower and more accurate top speed.

But what does concern me is that 2x170hp is an not a lot of horsepower to haul around a 6 ton boat. Might be OK for the river but could struggle with some cruising gear / crew / fouling. In comparison, smallest engines for Targa 34's were unpopular twin AD41's (2x200hp) with most buyers opting for 2x260hp KAD42's or 2x300hp KAD300's.
 
Kad32's should be adequate. Assuming no other faults the props changed to A4 may well sort it out. I imagine the existing props are not A4 .
 
30/32 knts with Kad32's in the real world is not realistic. 27knts down hill with the wind behind you is just about possible. Should pull around 3800RPM. If 30knts plus is a deal breaker than an S34 with Kad 32's is not the boat for you. If on the other hand if you want a spacous practical comfortable "general purpose" cruiser then maybe it is.
 
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