What props have I got? (Volvo duoprop)

alt · 24 March 2007, 22:54

Hi guys,
Currently running a Volvo KAD32 with duo props. The problem is that she should be achieving 3700 - 3900RPM WOT but i'm only getting 3000RPM, i'm obviously over pitching.

The only code I could find on my props was A5F 854778, which was on the forward prop

Can anyone shed some light on what pitch props I have? Or know a database online where I can find out??

Many thanks in advance!

alt · 24 March 2007, 23:03

Found a bit of information here: http://www.volvo.com/vce/vebiz2webau...0Volvo%20Penta

I've found the prop's that I have, but what I can't fingure is whether to move up to the A6 or move down to the A4 etc...

Any guru's out there?!

jwalker · 24 March 2007, 23:42

Alt, I can't tell you what to move to, but A4 has less pitch than A6. Can you speak to the previous owner and find out whether the engine has never reached correct revs? If it performed satisfactorily for them, there may be a different reason for the current lack of performance.

You need to find the number on the rear prop. I have seen Volvo drives fitted with props of mixed pitches and it seriously damages the performance.

Going down from A5 to just A4 is not enough to regain 800revs.

alt · 25 March 2007, 08:52

Thank's j. Unfortunately, the previous owner isin't all that well informed. Most his answers were 'I left it to the engineer'.

I asked him what RPM he was getting at WOT, he said 'Cant remember but I was hitting 33 knots". I'm getting 33knots at 3000RPM

I realise going down to A4 from A5 isin't going to give me 800RPM, i'd just love to know how much RPM difference there will be by moving each A (ie. would A5 to A4 give me an extra 200/300/400 RPM)

jwalker · 25 March 2007, 12:50

Alt, you need the power curve to find out what power you're getting at 3000rpm and then an estimation of the correct prop can be made. Volvo prop sets are not cheap, it can be an expensive buisiness. Volvo have a technical department and they will put your numbers into a computer program which will give you your props specification. However, I found it not too accurate for a rib. I felt I could guess better.

I'll see if I can find the phone number for you.

jwalker · 25 March 2007, 13:25

Here ya go.

Phone 01923 228 544 ask to speak to John Glenny for a prop calculation. My guess is A3s and 36knts if your drive is 1.95:1. Note, I did say guess....

Here are your power curves and engine perfomance data.
You can see you will get another 25hp approx by proping to 3800rpm. Presently, you are substantially overloading your engine. The data shows 136hp at the prop for 3000rpm full load but for normal use it should be only 89hp. Also your fuel consumption is way higher than it needs to be.

Mollers · 25 March 2007, 13:45

Quote:

Originally Posted by alt

Hi guys,
Currently running a Volvo KAD32 with duo props. The problem is that she should be achieving 3700 - 3900RPM WOT but i'm only getting 3000RPM, i'm obviously over pitching.

The only code I could find on my props was A5F 854778, which was on the forward prop

Can anyone shed some light on what pitch props I have? Or know a database online where I can find out??

Many thanks in advance!

I doubt whether prop pitch is your problem. If it were so over-propped as to be losing 900rpm it would struggle to even get on the plane. Surely this would have been addressed at some point in the past. I'd take a look at other reasons in the engine dept. Those things have electronic rev. limiters which are prone to playing up.
Or, possibly, the guy you bought it from has nicked the correct props off of it and put the original fitments back on. Do the props look newish?

jwalker · 25 March 2007, 13:53

Quote:

Originally Posted by Mollers

.. If it were so over-propped as to be losing 900rpm it would struggle to even get on the plane.

You would think so but when I was setting up my boat I had exactly the same problem as Alt, but worse. I could only pull 2700rpm and flat out at 27knts. but it lifted onto the plane smoothly and easily. I agree though, checking everything else before spending money is a good idea.

Mollers · 25 March 2007, 14:01

Quote:

Originally Posted by jwalker

You would think so but when I was setting up my boat I had exactly the same problem as Alt, but worse. I could only pull 2700rpm and flat out at 27knts. but it lifted onto the plane smoothly and easily. I agree though, checking everything else before spending money is a good idea.

But is Alts's labouring at 3000rpm or just refusing to rev any higher? Just to add to the confusion, those DP's run a different pitch on each prop. It may only be one that is wrong. I wonder if the previous ower is genuinely thick or being a bit cagey.

jwalker · 25 March 2007, 14:03

Quote:

Originally Posted by Mollers

Just to add to the confusion, those DP's run a different pitch on each prop. It may only be one that is wrong.

Yeh, I know, I mentioned that in my first post

but 800rpm is a lot to lose.

Mollers · 25 March 2007, 14:09

Quote:

Originally Posted by jwalker

Yeh, I know, I mentioned that in my first post.

Oh yeah, couldn't be arsed to read every detail of the thread. I leave it to you duoprop experts.

I'm more of a Mercruiser man myself.Apart from Bravo 3's.

alt · 25 March 2007, 22:07

Hi guys,
Thanks for all the info, including the power curve! (Very cool!)

To clear some things up....
The boat weighs 1900KG
She gets onto the plane VERY quickly, no problems there. Once she hits 3000RPM she stops revving on
Turbo seems OK, no dodgy smoke
The last owner has had the boat in the water for over 12 months, there was no prop changing

She is due a full service, I guess that the fuel filter could be blocked up.

I am going to give her the full service (Oil, Filter, supercharger oil, crank breather, gearoil, air filter, anodes - Anything else im missing?) next week and will report back.

I think I should be moving down to the A4 props either way, as the boat weighs 1900KG. What I can't get over is that even with that weight, the boat planes VERY quickly, even with 4 people on board

alt · 25 March 2007, 22:16

Quote:

Originally Posted by jwalker

You would think so but when I was setting up my boat I had exactly the same problem as Alt, but worse. I could only pull 2700rpm and flat out at 27knts. but it lifted onto the plane smoothly and easily. I agree though, checking everything else before spending money is a good idea.

Hi again j, firstly thanks for all the posts. I just spotted the above one. Seems to be my exact problem! Boat planes very easily and smoothly but just dies when she hits 3k. As said above, im going to give her a full service and see how she is then... Watch this space! (Well, next weekend anyhow!)

Mollers · 25 March 2007, 22:18

Quote:

Originally Posted by alt

Hi guys,
Thanks for all the info, including the power curve! (Very cool!)

To clear some things up....
The boat weighs 1900KG
She gets onto the plane VERY quickly, no problems there. Once she hits 3000RPM she stops revving on
Turbo seems OK, no dodgy smoke
The last owner has had the boat in the water for over 12 months, there was no prop changing

She is due a full service, I guess that the fuel filter could be blocked up.

I am going to give her the full service (Oil, Filter, supercharger oil, crank breather, gearoil, air filter, anodes - Anything else im missing?) next week and will report back.

I think I should be moving down to the A4 props either way, as the boat weighs 1900KG. What I can't get over is that even with that weight, the boat planes VERY quickly, even with 4 people on board

Umm, sounding more like an issue with the lump than props. It may need diagnosing after the oil/flter changes.

jwalker · 25 March 2007, 23:17

Quote:

Originally Posted by alt

..She is due a full service, I guess that the fuel filter could be blocked up.

Could easily be the case.

alt · 26 March 2007, 07:17

Quote:

Originally Posted by jwalker

Could easily be the case.

I suppose the chances that the tachometer is lying to me are slim? I say this because I notice that on idle, the engine seems to be happily turning over at 500RPM?!

Mollers · 26 March 2007, 07:32

Quote:

Originally Posted by jwalker

Could easily be the case.

I think not, a blocked fuel filter would cause to stuggle right through the rev range and more so at low revs.

jwalker · 26 March 2007, 10:58

Quote:

Originally Posted by Mollers

I think not, a blocked fuel filter would cause to stuggle right through the rev range and more so at low revs.

Would you like to explain your reasoning for that statement, Mr Moll?

Note point 6 taken from the Volvo manual.

jwalker · 26 March 2007, 11:19

Quote:

Originally Posted by alt

I suppose the chances that the tachometer is lying to me are slim? I say this because I notice that on idle, the engine seems to be happily turning over at 500RPM?!

All things are possible. Service it before you do anything else. The tickover speed should be 675-725. Mine can have the tickover speed set from the EDC controls, yours may be similar. The method is in the Operator's Handbook.

Mollers · 26 March 2007, 14:40

Quote:

Originally Posted by jwalker

Would you like to explain your reasoning for that statement, Mr Moll?

Note point 6 taken from the Volvo manual.

Experience Mr. Walker.