Hi
I was wondering if anyone could offer an opinion on my situation
I bought my
boat a 52 ft
motorsailer 45ft lwl/ 15 ft beam/ long keel/ 28 ton or 63000 pounds
I am chasing a vibration / rumble in the end of the drive train so as part of that search I wanted to ensure the prop was straight
I got the prop off on Friday and too it to Austral props in
Sydney for testing on Mon
the prop was 30 inch dia with 20 inch
pitch 3 blade
They say that the prop is a bit out but not too much - just like the three bears - one blade a little low one a little high one blade just right
The plot thickens - when I bought the
boat I was told that the
volvo (100 hrs old) had max revs of 2200, and that she should be cruised at max 2000
rpm
my
research shows that the
volvo (TAMD41P-A) is 200 hp and has max revs of 3800 / the
transmission is a PRM402 with 3 -1 reduction
Based on the Volvo max
rpm and 3/1 and boat spec - Austral did the calculations and are saying the the prop is too big
They are saying that a 25 dia with15
pitch will allow full horse
power to be developed.
I know that they are correct - however I am wondering if I want full
power as then I will be using a lot more
fuel to
cruise at the higher rpm.
Currently in still
water the boat will make 6.5 knots at 1500 rpm and 8 knots at around 2000 rpm
I think the
hull speed would only be about 10.5 so what I am asking is "am I doing anything to harm the Volvo in running it under these load conditions?" as it seems that the drive has been set up by the previous owner in its
current configuration and it is fairly economical.
The boat is intended to be used as a
family cruiser usually on week long local cruises in summer and once yearly 1000nm
passage to
great barrier reef for
winter
Thanks for any
advice
Neil