Volvo 2030 -> saildrive - economic revs

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fireball

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2000rpm drives at around 5 knots (flat water)
3000rpm reaches 7.5kts ...

has anyone concluded the most effective revs for their Volvo engine?

TIA

ps it's a 2 blade fixed prop on a saildrive ...
 
Yes, 2 bladed prop on a "heavy" Bavaria 37 clean bottom 2600 5.8 knots. 6.5 at 3000. Will run up to max 3600 about 7.8 knots. So plenty of reserve for normal cruising.

Your boat perhaps a tad overpowered which is why you can get 7.5 at 3000.
 
[ QUOTE ]
Your boat perhaps a tad overpowered which is why you can get 7.5 at 3000.

[/ QUOTE ] - nope - just a very clean bum and nothing on board!!
 
I am assuming this is the 30 footer in your bio. In which case the comment stands. 20hp (a 2020) is more than enough. You are achieving more than hull speed using less than 65% of the maximum power of the 2030.

I expect the displacement of you boat is around 3600kg light whereas mine is 5360kg. Max hull speed (based on 1.4*sq root WL) I estimate at 7.25 and 7.5 respectively.

So, if my installation can comfortably achieve hull speed with a displacement nearly 50% greater than yours, I suggest yours is overpowered. (In fact I expect the displacement of my boat in its current trim with full tanks is well over 6000kg)
 
2500 rpm = 5k
3000 rpm = 6k
flat out = 7.2 k but transom well buried

flat water fully loaded for cruising

Re your q. about economic revs we have averaged just under 12 mpg (2.5 mpl) over 4 years of use but little abuse i.e usually motor at 6k .... only hoofing it on rare occasions.

Are you going to tell Tranona what you've bought? /forums/images/graemlins/ooo.gif
 
It'll be interesting to see what she does now SWMBO and M-i-Law have filled her up ...

I think we'll stick to the 3000rpm and see how we go ... and hope we can achieve a similar 2.5L/hour ...
 
I am advised by volvo that 3500rpm is max revs for 2030, Any nore or any less (approx) the prop is not sized correctly. From memory 1800 rpm on my previous boat (Bav34) was most econimica at between 5/6 knots depending on conditions.
to test volvo say open throttle wide to check revs.
I have "Heavy" Bav. 37 - 8 ton + crew with D1-30 max revs. 3200.
2200rpm at 6 knots just for comparison.
 
Mine goes straight up to 3600 which is the governed maximum. Just as Volvo say, if it does that it is propped correctly. The later D1 30 is as you note a lower revving unit so guess they have probably gone up a bit in prop size - pitch most likely.
 
thats a heavy bav 37 - standard displacement is 5.4 tonnes isnt it? anyway, fwiw I get 6kn (gps in non tidal waters) at 2700 rpm from my 2030 with a 2 bladed folder on a starlight 35. standard displacement 6000kg or 6136kg or 6907kg or 7000kg depending on whether you believe ST or PBO or Rustler or my IRC cert. plus 10 years of accumulated and flaking antifoul. lets hope the clean off which starts tomorrow will help me get nearer your figures.

if the max revs are 3600 the usual rule is the max continuous is 80% of that ie 2880

why are boat dimensions so difficult to get consistent figures for?
 
Your performance souns about right. Difficulty in getting reliable dimensions is easy. Depends on the purpose. For sales pitch one might want to exaggerate (35 footer may be only 34 ft on deck), minimise for such things as registered tonnage or marina fees, fit certain parameters for rating, light displacement, loaded for cruising etc. (full tanks on my boat adds 450kg, over 8% increase to published displacement).

Most importantly on older boats designed before the advent of CAD packages, the designers and builders usually "guessed".
 
No - the latest B37 is listed as 7500kg. + 1000 person and equip.
Mine was lifted to scrub and crane digital recording was 8ton.
 
Just found an answer to my own question - you can get the correct weight from the RORC if someone has gone for an "endorsed" certificate which means a weighing on a calibrated weighbridge. Cranes are simply not very accurate - we have several boats in the club which weigh 50% more than their standard displacement on the cranes we hire in at launch and recovery.

The official manufacturers weight for your Bav 37 is 6.9 tonnes. Interesting - most boats get lighter as they develop not heavier. Is it a "big" 37 ft?
 
Yes, the 2005/7 37 is a very different boat from my 2001 model. 1m longer on the WL, wider beam and heavier displacement. Very similar to the 38 of the same age as mine - a much bigger boat.

This illustrates the difficulty of using the headline size as a basis for comparison. On the other hand my boat has a ballast ratio of 34% compared with the later model of 29%. Some might say the higher ratio is better, but others might admire the vastly increased interior space of the newer model!

Me? - I think my boat is the dogs whatsits for me! Every time I use it it I marvel how good it is, particularly as to replace it with a later model would cost me as much again as I paid for it.
 
[ QUOTE ]
It'll be interesting to see what she does now SWMBO and M-i-Law have filled her up ...

I think we'll stick to the 3000rpm and see how we go ... and hope we can achieve a similar 2.5L/hour ...

[/ QUOTE ]

Forgetting the revs question for the moment, fuel consumtion is not necessarily related to the revs, but to how hard the engine is working. When you call for 3000 rpm on flat water, you may only be using 50% of power. Running into a F8 and a sea, may mean that it is delivering 90% power. So you will be using at up to double the fuel;- worth remembering if you have a long motor to windward, as it could knock a hole in your fuel usage calculations.......
 
I have to say I was slightly surprised at the gross weight but the crane has as a requirement have a calibration cert. as the fees are charged on weight in our local commercial harbour.
However the displacement is listed as 7500kg in my Bavaria documentation so it can't be far out. I suppose with bow thruster and extra batteries adds a little extra.
I also note in the new Bav brochures the weight is listed at 6900 .
Must look out more info out of interest - mine is 2006 model.
 
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