Volvo Penta C Series Duoprops

Is there a particular reason that you have the C-series props?
We used to have a Fairline Targa 35 with twin KAD42’s and she had B5 props, which is what your boat had out of the factory. Notwithstanding the possible turbo issue perhaps the B5 were better suited?
 
You could very well be right, I got the boat with C3's on and moved to C4 as a natural progression. Truth is I didn't really give much thought to going back to B's after speaking to Formula. B5 just seemed a stock choice. If I had to give a reason I didn't go back to B series is, longevity of the prop and the fact that according to Volvo the recommendation for moving from B's to C's in terms of Hp showed B's being marginal (IIRC it was 230Hp or 35knts) with blurb about the rear prop having to have a fine blade on the duoprop (i.e. they cant beef it up) A friend who is on B series but admittedly on KAD44's chews through props every couple years. If C5's dont pan out I might give it a try but would rather have a constructive approach to prop selection than shoot from the hip by starting on a new series.
 
After many years with the C4 and having them checked/refurbished every 2yrs I concluded it was better to get the more "disposable alternative" in the new J series and simply buy new ones when needed. It seemed there would always be something finding its way to the props and messing them up. There were also constant issues with making sure the galvanic isolation was still intact, you will find that the anodes last much longer without the c series.
The main reason though was to protect the drive if hitting something solid at high speed, the C series are very strong and its better/less costly that the props break vs the drive, happened to me and for the same cost I could buy a lot of J series props.
In general I think the C series is only needed/recommended for the KAD44 or 300 and boats doing 38+ knots.
 
'C' series are stainless steel and are required for engines producing more than 240hp (I believe). That's why they are standard for for KAD44's.

If your engine is less powerful then I would have thought that cheaper 'A', 'B' or 'J' series props would be adequate.

But I agree wholeheartedly with the comments above. Get the engine working correctly (particularly superchargers and turbos) before messing about with different props.
 
I may have this wrong. But when you say the boat was supplied with B5 Props out the factory...is this 100% ? I thought the B series were ally Props for petrol engines, both with 3 blades. And the A series was for diesel, one with 4 blades and the other with three.
C series obviously Stainless versions of both ?
 
Other way round. B for diesels. Yes really, I spoke with Formula TAG. Credit where it's due, they were fantastic and not only supplied prop data etc but also supplied every CAD drawing, wiring diagrams, plumbing you name it of the boat including photos of the build when I asked for original engine room layout. 26 years old mind, their records are meticulous.
 
Some diesels did or could also, take A according to the 2006 prop charts. KAD32 being one. I'm surprised, learnt something new. But no, mine were B5
 
QBhoy said:
I may have this wrong. But when you say the boat was supplied with B5 Props out the factory...is this 100% ? I thought the B series were ally Props for petrol engines, both with 3 blades. And the A series was for diesel, one with 4 blades and the other with three.
C series obviously Stainless versions of both ?
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Prop guide said:
A-Series: AD31, AD41, KAD32 etc.
B-Series: Petrol Engines plus KAD42, KAD43, KAD44
 
BruceK said:
Other way round. B for diesels. Yes really, I spoke with Formula TAG. Credit where it's due, they were fantastic and not only supplied prop data etc but also supplied every CAD drawing, wiring diagrams, plumbing you name it of the boat including photos of the build when I asked for original engine room layout. 26 years old mind, their records are meticulous.
Click to expand...

Bruce I had B5’s on my 4.3 VP petrol Sealine. My friends still has. Other friend had a cruisers 224 with a VP ad31 and had A4’s
 
BruceK said:
For reference in case anybody else has the same question. I got these measurements from pattern props of the C series so may not be 100%

Diameter does not change from C3-C6 they are a constant 15" front 13" rear

Pitch changes
C3 17 19
C4 19 19
C5 19 21
C6 21 21
Click to expand...
BruceK said:
to add. The boat was supplied with B5's straight out the factory which I am led to believe equates to a C4, however I understand that the rear prop on a B5 set is 3 inch coarser than the C4 equivalent.
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Hello BruceK, just came across this forum, as I'm looking for a piece of advice from more knowledgeable sailors here. My boat was equipped with B4 set when I got it, donnow what was an original prop set, but last winter I got a set of C5s and installed them. The time weather was permitting I have the boat on the water and found out that the prop set is too heavy ( too coarse ) for my application. Its getting on the plane very hard and WOT is 3100 rpm top with speed around 30 miles/hr. With B4 it was going around 40 miles/hr with WOT 4000 rpm. Should I replace it with C3 to get faster on the plane and to have top-end speed like with B4? Thank you in advance.
 
Yeah, looks like it should fit well. Well, thought C5 will be good as well but turned out it's not, a bit confused.
 
C3 is finer than B4 by about 250 rpm at least on my boat. Getting on the plane was almost instantaneous but cruise revs was dismal. I had to push WOT to make any decent cruise speed. Nice thing about C3 for me was you could travel any speed within its range without lugging the engine. KAD42 x2 on 34ft 8 ton sports cruiser
 
However, B4 is about 150 rpm finer than C4. Between the C series on my boat I found that there is close to 400 rpm difference between sets. If you are UK based and want to try a set of C4 I have two pairs for sale that you can try on buy or return basis. C series have much more bite and will get you to plane quicker, not like C3 obviously, but more than B4. PM me if you wish to try C4s
 
Thank you, Bruce, Im in Canada, on Lake Simcoe, a bit far from UK, but thank you for your offer. So, what I understand from your message, the boat, mine is Wellcraft Prima243, powered by Volvo Penta 5.7 GL w DP outdrive. So, between C4 and C3 the C4 looks like a better choice . From the pitch table
Pitch changes
C3 17 19
C4 19 19
C5 19 21
C6 21 21 going down from C5 to C3 im changing the pitch on both props, for C4 I only change the pitch on rear prop. With C5 the engine was lagging very bad 3100rpm top on max open throttle, even boat being on the plane. It won't go any faster than 30m/hr. I have to add basically at least 1100-1300 rpm. It seems like C3 would be a better choice in this case. I donnow, totally confused.
Btw, how much you selling those C4s for?
Thanks, Kepin
 
If my math correct, going from C5 WOT = 3100-3200 to C3 two inches on each prop equal 4 inches will give me roughly + 800 rpm, which will bring me to about 3900-4000rpm on full throttle. Am I correct on my calculation?, or its not linear correlation?
 
I think I have solved the mystery of my C5 prop. Just got off the phone with the prop guy from Florida, he said that most likely the props were repitched to much the engine, which was a high-performance 500hp engine on the boat that those propellers were off. The guy who sold me those props didn't mention the repitching, but he said the engine in a crate that was sitting in his garage was a high-power unit and the props meant to be fitted on it. Now it just makes sense, why such a drop to 3100 in just one step from B4 to C5, it most likely is C6 or even C7 in reality. wow, something new to learn every day.
 
I think your prop guy is right and the blades cupped. Id certainly find it odd for you to be running C3 given your boat, power and speed. But then again, when it comes to props I am constantly surprised at what gives best performance. Everytime I think I have a handle on it something comes along to make me rethink things.
 
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