Propellor Comparisons

[richardbrennan]

I am in the process of replacing the Volvo 2030 in my boat with a new Volv D1-30. Unfortunately the new engine has different characteristics in that it revs slower (32-3600rpm) and has a different drive ratio (2.19-2.47). I currently have a Volvo 17x11 three blade folding propellor and the nice man at Castle Marine, (my computer would not run the programme with Windows 7), tells me that their prop calculator comes up with a 15x12. My question is would the increased diameter of my prop more or less compensate for a reduced pitch; replacing the blades on the Volvo prop, as with all things Volvo, would be expensive!

 

[Quandary]

I can not help with the prop but I have been using a D1-30 for five years now and rarely run at over 3000 revs except for a half hour work out once a month or so. The engine seems quite happy at around 2000 revs with plenty of torque; increasing the revs to 3000 takes the boat speed from 6.5 kts to 7.5kts and the fuel consumption from 2 litres per hour to 7. It also produces a lot more heat and noise. I get a resonance in the cockpit steps at aroundv 2,250 revs so i prefer to stay below that. I love the engine for the way it produces power while purring along silently so I am prepared to ignore the advice that it should be worked much harder for longer life before the bores glaze, if I have to get them honed in ten years time I will have saved enough fuel to pay for it. Mind you, I rarely ran the 2003 that preceded it at 3000 revs either. The current prop is a VP 3 blade folder and after five years use I still love it.
I am suggesting that you consider sizing your propellor for much lower revs but I am sure others may contest this advice.

 

[scottie]

If the Volvo dealer who signs off the installation would accept not reaching full revs then it might be worth trying but if not your warranty may be void

New blades are the correct option I would suggest.

 

[richardbrennan]

I hope my understanding is correct, but although the engine runs slower, the reduction ratio is less so the prop at any given rpm will be turning faster or have I got this the wrong way round?

 

[Tranona]

Yes, the shaft speed is the same (virtually) 1460 compared with 1480. I would stick with the 17" prop. Ask the Volvo dealer for their recommendation, they have a calculator. On mine I went down from a 16*12 to a 16*11 to compensate for the higher shaft speed (1640) in my combination. However as you are not changing shaft speed or max power, if the 17*11 worked, stick with it.