Princess 32

[longreach]

Hi. I am new to the forum and I wondered if anyone has any information regarding suitable prop size for my "new" boat. She runs on twin 75HP Volvo pentas AQD21s with 280 outdrives. Main area of sailing would be rivers, canal and estuaries.

Thanks for your help

 

[longreach]

The ones that are fitted are 14x13 and seem a bit slugish (they are a bit worn)

Any help would be gratefully received

 

[Andrew_Fanner]

The ones that are fitted are 14x13 and seem a bit slugish (they are a bit worn)

Any help would be gratefully received

Welcome to the forum1

What are you expecting from them? Those engines will only give you hull speed and a wee bit more.

 

[Chris_d]

Size sounds about right, you are unlikely to get much better than 10knts with those engines given the age.

 

[longreach]

Welcome to the forum1

What are you expecting from them? Those engines will only give you hull speed and a wee bit more.

This is the problem, I have no idea what to expect from which size of prop. I just needed to know which size of prop would be most suitable for the given conditions. Even contacting Princess themselfs was no help whatsoever as they failed to answer!
Thanks to you both for your answers.

 

[CX54WEK]

Without sounding rude, what exactly are you expecting from a pair of 75hp engines?

For the size of boat they are certainly more suited to river and estuary cruising and wont give blinding performance. If your current props are a little dinged, send them for refurbing this may help slightly but wont work miracles.

 

[carlton]

Some info available here -

http://www.jonesboatyard.co.uk/boat-sales/princess-32-boats-for-sale.html

Scroll down to Princess 32 Documents & Original Brochures - there's a downloadable pdf with lots of info re. the engine options and performance.

 

[longreach]

Without sounding rude, what exactly are you expecting from a pair of 75hp engines?

For the size of boat they are certainly more suited to river and estuary cruising and wont give blinding performance. If your current props are a little dinged, send them for refurbing this may help slightly but wont work miracles.

As I said, I have no idea really, I know they are not the most powerful of engines but wondered what was the best size of props for this model for the aplication I previously mentioned.

Some info available here -

http://www.jonesboatyard.co.uk/boat-sales/princess-32-boats-for-sale.html

Scroll down to Princess 32 Documents & Original Brochures - there's a downloadable pdf with lots of info re. the engine options and performance.

Yes, I've seen this but doesn't mention props........but thanks anyway.

There seems to be some confusion as to what I am after.

The props I have on are 14x13 pitch, the other options I have (from Volvo) are 15x11 and 15x13 all 3 are standard, there are others but are classed as "high speed" which I assume are not relevant to my boat.

 

[CX54WEK]

If you have no idea what to expect from your boat how do you know it is sluggigh?

 

[longreach]

If you have no idea what to expect from your boat how do you know it is sluggigh?

If you read what I said "seems a bit sluggish" meaning it may be, it may not be........this is why I ask questions.

Thanks for your help.

 

[jfm]

The ones that are fitted are 14x13 and seem a bit slugish (they are a bit worn)

Any help would be gratefully received

Longreach, do you know what rpm your engines reach at WOT with the normal weight (people and gear) on board? If they are reaching the correct rated rpm for the engines then the props are broadly correct and you have nothing to gain slug-wise by changing them. If the engines reach too high or low rpms then the props could be wrong (or of course you might have a quite separate engine fault, though in that case you will generally see a different rpm on each engine)

 

[BGW]

If you read what I said "seems a bit sluggish" meaning it may be, it may not be........this is why I ask questions.

Thanks for your help.

Do you have a GPS unit - either on the boat or your mobile phone - so you can give us some speeds and at what engine RPM you achieve them - This will be a good starting point in figuring out how well things are working right now.

Also, growth on the hull can be a massive problem. - Is the boat clean underneath? - If not you need to start there before worrying about the props.

 

[longreach]

Longreach, do you know what rpm your engines reach at WOT with the normal weight (people and gear) on board? If they are reaching the correct rated rpm for the engines then the props are broadly correct and you have nothing to gain slug-wise by changing them. If the engines reach too high or low rpms then the props could be wrong (or of course you might have a quite separate engine fault, though in that case you will generally see a different rpm on each engine)

Four people on board 3500 rpm on both engines, reading about 10/11 knots (if accurate on the speedlog) at 1800/2000 rpm about 5 knots.

Had it up to 4000 rpm but didn't seem to make much difference.

Is this helpful?

 

[longreach]

Do you have a GPS unit - either on the boat or your mobile phone - so you can give us some speeds and at what engine RPM you achieve them - This will be a good starting point in figuring out how well things are working right now.

Also, growth on the hull can be a massive problem. - Is the boat clean underneath? - If not you need to start there before worrying about the props.

Underneath is "brand new" as just been antifouled and hull polished.

Good idea on the gps, I'll try it, be a bit more accurate than the dithering speedlog.

Cheers

 

[CX54WEK]

Four people on board 3500 rpm on both engines, reading about 10/11 knots (if accurate on the speedlog) at 1800/2000 rpm about 5 knots.

Had it up to 4000 rpm but didn't seem to make much difference.

Is this helpful?

Sounds about right.

You wouldn't expect much more than 10 knots from that boat with those engines and the last few hundred revs wont do much more than squat the arese end into the water and make more wash.

 

[longreach]

Sounds about right.

You wouldn't expect much more than 10 knots from that boat with those engines and the last few hundred revs wont do much more than squat the arese end into the water and make more wash.

So what affect would putting a pair of 15x11s on or a pair of 15x13s have?

 

[carlton]

...Yes, I've seen this but doesn't mention props........but thanks anyway...

The pdf in that link says, "Volvo D21/280... with a maximum speed in the region of 10 knots...", so I'm not altogether sure what you would be hoping to gain by playing with the props - I'd have thought if Princess reckon you'll get 10 knots with that set up and you're getting 10 knots, that's about as good as it gets.

Were you hoping for better economy/speed than you have currently?

BTW, not sure where you were doing 10 knots, but I assume you allowed for the effect of any tide running at the time?

 

[longreach]

The pdf in that link says, "Volvo D21/280... with a maximum speed in the region of 10 knots...", so I'm not altogether sure what you would be hoping to gain by playing with the props - I'd have thought if Princess reckon you'll get 10 knots with that set up and you're getting 10 knots, that's about as good as it gets.

Were you hoping for better economy/speed than you have currently?

BTW, not sure where you were doing 10 knots, but I assume you allowed for the effect of any tide running at the time?

Just on a non tidal stretch of a river and only briefly to avoid damage to bank sides etc.

Trying to find the most suitable set of props for economy and speed, in other words which are the most ecconomical and which ones would chew the fuel but give a good top speed.

 

[CX54WEK]

If your current props are giving you the quoted top speed then changing them wont improve matters any.

Is your current fuel economy bad?

 

[Chris_d]

Just on a non tidal stretch of a river and only briefly to avoid damage to bank sides etc.

Trying to find the most suitable set of props for economy and speed, in other words which are the most ecconomical and which ones would chew the fuel but give a good top speed.

From the speeds and rpm you have quoted your boat is performing as is should, changing props will make little difference especialy at displacement speeds. The most economical speed regardless of props will be just below hull speed which for a 32footer will be about 7knts, any faster and your just pushing water and burning fuel at an exponential rate for every extra knot achieved, you will need twice the horsepower too reach planing speeds and then start to see the economy improve again.

Honestly you will not see any meaning full increase in efficiency changing props better to save the money for servicing the outdrives the options you listed are all very similar and which you fit will depend on where you use the boat, short pitch to increase the revs a bit for good low speed handling on a speed resticted river or long pitch to allow a slightly higher cruising speed at sea but your only talking maybe 1 knot difference with a P32 and 2 x 75hp.