Princess 32

[BGW]

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

The first number is the prop diameter, the second number the pitch - you could think of this as the 'gear ratio' - the higher the number, the less revs will be required to reach the same speed - but you still need the pitch to be matched to the boat/engine combination.

If you can reach max revs there is no point putting the 11 pitch props on - and I doubt you will get more speed with the higher pitch. - If you can get them changed with little or no cost then it's worth a try.

 

[longreach]

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

Is your current fuel economy bad?

Possibly about 4lts per hour averaging 5/6 knots (both engines running) so bad compared to my last boat that did 1.5 ltrs per hour.

I do appreciate that I now have a bigger boat but don't know if the fuel consumption for this is good or bad and what affect changing the props would have.

 

[longreach]

The first number is the prop diameter, the second number the pitch - you could think of this as the 'gear ratio' - the higher the number, the less revs will be required to reach the same speed - but you still need the pitch to be matched to the boat/engine combination.

If you can reach max revs there is no point putting the 11 pitch props on - and I doubt you will get more speed with the higher pitch. - If you can get them changed with little or no cost then it's worth a try.

Thank you, this is what I was looking for! Great stuff.

 

[Chris_d]

Possibly about 4lts per hour averaging 5/6 knots (both engines running) so bad compared to my last boat that did 1.5 ltrs per hour.

I do appreciate that I now have a bigger boat but don't know if the fuel consumption for this is good or bad and what affect changing the props would have.

4lts per hour at 5/6knts is about bang on for that boat in fact it is better than most. If you cruise at 7knts your 4lts will probably have doubled, at 10knts its likely to be about 25-30lts/hr.

 

[longreach]

4lts per hour at 5/6knts is about bang on for that boat in fact it is better than most. If you cruise at 7knts your 4lts will probably have doubled, at 10knts its likely to be about 25-30lts/hr.

Thanks for your help.

 

[CX54WEK]

4lts per hour at 5/6knts is about bang on for that boat in fact it is better than most. If you cruise at 7knts your 4lts will probably have doubled, at 10knts its likely to be about 25-30lts/hr.

You beat me too it. Both engines running and 4 litres per hour aint half bad.

We look at about 3-4 litres per hour at 5 knots with our single engine!

 

[Tom Price]

If . . .

. . you won't sleep at night without speaking to a professional then contact Andy Childs at Clements Engineering tel 01234 378814 - top notch.

 

[Dave_Seager]

As already stated, the performance of your boat sounds pretty good for the set up that you have.

I have a Princess 32 with the AQD32A engines, rated at 106 hp. A friend used to have one with AQD21As, like yours. Mine will plane, getting to 16 knots in ideal conditions and lightly loaded. In normal cruising trim she can do 14 knots. My friend's with the smaller engine would not plane and the top speed was about 10 knots. Even so, he managed to take her round from the Thames along the south coast, round to North Cornwall and back again a few years ago.

When I bought my Princess, the previous owner had fitted finer pitch propellers for river use. I think that he found the speed at tick-over was too fast for him when entering locks. I replaced the propellers with some of the original pitch as I go down to the tideway quite often and wanted the full performance again. At tick-over she runs at about 2 knots but I just go into neutral occasionally if I need to go slower and have not found it a problem.

 

[carlton]

More info could be found here...

Princess Owners Club Forum.

...although it hardly looks a hive of activity.

 

[Alpha22]

. . you won't sleep at night without speaking to a professional then contact Andy Childs at Clements Engineering tel 01234 378814 - top notch.

Andy has unfortunately left Clements and moved on...... They are still a top company and highly recommended. Their expertise in the leisure boat industry is second to none.

 

[oldgit]

A little more info on the P32

and its predecessor

 

[jfm]

Please correct me if I'm missing something but I don't think the "everything is as it should be" posts are correct. This is a 2x75hp boat, and Oldgit's brochure says it should do 18-20. Call that 17, allowing for marketing exaggeration. The boat has a clean bottom. Yet OP is actually getting only 10kts ish at 3500 to 4000rpm. Both engines are the same, so it doesn't sound like there is an engine fault

The way to verfiy would be to look at the fuel flow rate to determine the hp developed by the engines, but we don't have the data. But this feels very much like underpropping to me. I reckon OP needs to get a pair of props with another 2 or 3 inches of pitch. I'd buy a pair of 14dia x 15P

 

[macnorton]

Possibly about 4lts per hour averaging 5/6 knots (both engines running) so bad compared to my last boat that did 1.5 ltrs per hour.

I do appreciate that I now have a bigger boat but don't know if the fuel consumption for this is good or bad and what affect changing the props would have.

I have a simular boat (well the same hull), your consuption / speed seems about right.
Reaching 4k under load means it is under-propped a little.

If you wish to do a lot of high speed use I would increase the pitch or diamiter of the props, but this will ruduce slow speed boat control.

if you do a lot of slower river use I would leave them alone (have them overhauled in winter if you like)

Full power with both engines will use 8 - 10 Lph for an extra 2-3 knots and big holes behind you (the guy who quoted 25-30 Lph must have been at the gin!).

Don't pay to much attention to the speeds quoted in advertising, these people are trying to sell boats.

Good boats - enjoy...

 

[jimg]

Please correct me if I'm missing something but I don't think the "everything is as it should be" posts are correct. This is a 2x75hp boat, and Oldgit's brochure says it should do 18-20. Call that 17, allowing for marketing exaggeration. The boat has a clean bottom. Yet OP is actually getting only 10kts ish at 3500 to 4000rpm. Both engines are the same, so it doesn't sound like there is an engine fault

The way to verfiy would be to look at the fuel flow rate to determine the hp developed by the engines, but we don't have the data. But this feels very much like underpropping to me. I reckon OP needs to get a pair of props with another 2 or 3 inches of pitch. I'd buy a pair of 14dia x 15P

I think " marketing exaggeration" is just about right! Had one of these many, many years ago and I remember the wild excitement from the children when we once hit 12 knots!!

 

[CX54WEK]

I think " marketing exaggeration" is just about right! Had one of these many, many years ago and I remember the wild excitement from the children when we once hit 12 knots!!

With the wind and tide behind you

 

[Chris_d]

IFull power with both engines will use 8 - 10 Lph for an extra 2-3 knots and big holes behind you (the guy who quoted 25-30 Lph must have been at the gin!).

No not been at the gin, I wish rule of thumb is 5gph/100hp so 2x75hp = 7.5gph at wot = 34lph, so I think it was a good estimate for flat out consumption as its unlikely they are still 75hp each and he is never going to run at 10knts continuously anyway. As you say the original advertising is fiction I doubt a P32 ever did 18-20knts with 2 x75hp.