Cruising Speed Princess 33?

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Marco69

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I have recently purchased a MK1 Princess 33 Flybrige with twin shaft 130 TD mermaid engines. While checking her out I got her up to over 20 knots at approx 2400 rpm(not GPS). I noticed the turbos did not really start showing on the guage until over 2000 RPM. My question is, should I be cruisng at over 2000 RPM to get best efficiency? I would have thought this a bit high, but surely it would be better for the turbos to be doing some work. I am new to this and only have a basic knowledge of engines. Any advise would be appreciated
 
If these are the 4 cylinder Mermaid Turbo Merlin, they should reach 3800 RPM !!

http://www.mermaid-marine.co.uk/documents/TurboMerlin1.pdf

... Sorry to potentially be the bearer of bad news, but if this is the case, you are seriously over propped and are heading for arrival of Big Bill !!!

Your propellors then need to be re-sized to fit the engine's expected WOT at 3800 RPM .... and cruise load would be somewhere around 3000 - 3400 RPM.

Don't expect a lot more speed from higher RPM, but your engines won't get killed (read ££££) by overload...
 
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I doubt if you would ever get up to that speed, in a P33 with those engines.

Remember, rev counters are totally unreliable,as are speed logs.

Cant remember the details now, but I once had a P33 Fly, Volvo 130 hp on drives, which should be quicker. Would do 18 knots on a good day, but cruise all day at 16 knots.

Know nothing about your engines, but the usual cruising speed is, 200 revs less than WAT, or in other words, 200 revs less than flat out. Mind that presumes your engines are still working to full power. I suspect they are not.

Look at all four of your rev counters, do they all show the same?? I suspect not.
 
Divemaster1 said:
If these are the 4 cylinder Mermaid Turbo Merlin, they should reach 3800 RPM !!

http://www.mermaid-marine.co.uk/documents/TurboMerlin1.pdf

... Sorry to potentially be the bearer of bad news, but if this is the case, you are seriously over propped and are heading for arrival of Big Bill !!!

Your propellors then need to be re-sized to fit the engine's expected WOT at 3800 RPM .... and cruise load would be somewhere around 3000 - 3400 RPM.

Don't expect a lot more speed from higher RPM, but your engines won't get killed (read ££££) by overload...
Click to expand...


Well I thougth that might be the case, but cant remember now.

But I would have thought 3400 Revs would give about 14 or 15 knots?? Maybe a bit more flat out??
 
Lightweight engines, could give an edge on HP to weight ratio...

Had an Apollo 32 with two Ford straight 6's non turbos @ 120 hp ...did 21 knots (measured NM both ways with stopwatch) and on Autopilot ... low fuel, water and clean bum .... so suspect OP's posting represent a possible max with more modern, lightweight engines.... In the Apollo, we cruised at 15 - 16 knots at 2100 - 2200 RPM (2500 max)..

Irrespective, sounds like OP have some issues to resolve....
 
Princess 33

Many thanks,
I am in agreement with Divemaster, last boat was a 36' heavier boat with twin 150 hp version of engines. Max ever revs was 2500 and achieved 17 knots one day. While I do know speed guages are less than realiable the new boat is definately much quicker. My main question however was, should I increase revs to bring the turbos 'in' to achieve fuel efficiency. I am intending a 150 mile journey soon and would like to do it with least pressure on the boat and good efficiency.
Thanks for the input
 
"Any advise would be appreciated"

Is her bottom clean ?

My P33 with 130HP AQD40A could reach 16 knots on a good day with average fuel/people/weed/junk on board
p33.jpg

With a dirty bottom we struggled to get to 12 knots,what happens when you apply WOT when not in gear does it get up to full revs then,a quick burst will do to check ?
 
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Marco69 said:
Many thanks,
..........., last boat was a 36' heavier boat with twin 150 hp version of engines......... My main question however was, should I increase revs to bring the turbos 'in' to achieve fuel efficiency. I am intending a 150 mile journey soon and would like to do it with least pressure on the boat and good efficiency.....
Click to expand...

OK, If they are Turbo Four 130's (Spec sheet, with fuel info here... http://www.mermaid-marine.co.uk/documents/TurboFour.pdf ), then you are in the right ballpark for the WOT....

Surprised by late turbo kick in though ... would have expected that to be kicked in at about 15 - 1700 RPM (Very different engines, but ours kick in at about 1250 RPM and we max out at 2300 RPM).

Fuel efficiency will be best at hull speed... which at 33 foot is around 6 knots.... Engines should (if they are Turbo Four) run comfortably at 2100 RPM all day long... but you'll burn more fuel at that speed....
 
Many thanks for the info,

:)you have answered another question. I wanted to know if the engines would run for extended peiods at 2000-2200 range without harm.
 
They are both "Turbo 4 cyl" but one is 254 Cu/In (4.5ltr) the other is 144 Cu/In 2.5l a very different kettle of fish ! The 2,5 is same as previous level Transit van, The older "Dover 254" is a "Proper" truck engine.
 
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