Help Volvo Props!

[Johntheoil]

Just about to launch the boat.....always an exciting and 'stressfull' time

This year we thought we would try some 'lower pitch props', to try and get a bit more 'useful performance'....not looking for any extra speed, but we always struggled to get close to max revs at wot even freshly launched, light and with a clean and fresh bottom.
When we filled with fuel, beer, or had some fat friends aboard......it was a sloooooow!

Just having major doubts, as the new props (IH4's fresh out of the box) look bigger than the old ones which were (IH5's):ambivalence:
So having a bit of a panic, if we are going in the right direction......or should we be going to IH6's?
How do the Volvo number codes work?

Unfortunately our local Volvo dealers have gone AWOL for the long weekend.......the 'online' Volvo Penta prop guide, only seems to give diameter/pitch numbers for the older props, and only serial numbers for the newer ones.

 

[Momac]

I am not familiar with IH props.
But the usual Volvo Penta numbering arrangements make '4' a lower pitch than '5'

 

[oldgit]

Ebay is full of.... "thought we would try some ' ???? pitch props',"

Volvo probably spent zillions along with the builder of your boat getting the optimal prop pitch/blade choice for 99% of the boat operating conditions.
The logical result of experimenting with props is to have a dozen sets aboard.One,light boat no water no fuel,right through to full everything including booze cupboard and Auntie Bessie aboard who really does like her pies.
Plus a few left field option for dead calm/rough weather possibilities.
Ps.your choice of prop for el Prop del Dia will of course need to take account of all those extra props you will have aboard.
Down this path lies frustration for you and untold wealth for propeller sellers.Feel sure that JFM must be selling aftermarket propellers

 

[neale]

It's not unusual for boats to be more heavily loaded than a builder anticipated, leading to engines not making max rpm. As long as you have discounted any other reason for not making full rpm then the pros are clearly wrong for your particular boat/usage. Assuming IH props are like Volvo's other duo props, (I have no experience of IH, only A, B and C series), 4 should be a finer pitch than 5 and should increase your max rpm by about 200. The physical size of the pros won't change, as the diameter will probably be the same, so you can't really tell by looking.

How far down on max rpm are you?
Can you find some slimmer friends? ��

 

[Johntheoil]

Thanks Neale. That's very helpful. There are 3 versions of this boat ( Sessa Key Largo 34), twin outboard, petrol stern drives, and diesel stern drive. I have the diesel with 2x220hp D3's on DPS drives.
According to the builders own figures, the 'planning' speed of the petrol versions is 14kts.......but the diesel only starts planning at 19kts........which seems to be true from my experience, presumably because it's heavier?
All versions have a big fuel tank for the boat size (1,100ltrs), and ours has a genny and a/c so guess it's even heavier!
The only time we've seen 4000rpm was once with clean props/hull........and 5 mins later we ran out of fuel
Normally only getting around 3500rpm at wot.
Not sure about ditching my 'fat' friends though.......stops SWMBO noticing MY 'tummy':nonchalance: