Pod drive efficiency

[Deleted User YDKXO]

I have just finished reading the latest MBM test of the Prestige 550 which is fitted with 2 x Cummins 600hp engines and Zeus drives. This boat is similar in size to my Ferretti 53 although, apparently, it weighs about 6t less. My boat is fitted with 2 x Cat 660hp engines and standard shaftdrives.
According to the MBM test the P550 consumes fuel at around 0.63nmpg at between 20 and 25kts and maxes out at 30kts. On the other hand, my boat consumes fuel at about 0.67nmpg in the same speed range and maxes out at 31kts and that is with all our cruising stuff on board. So despite being 6t heavier and having shaftdrive, my boat consumes less fuel at typical cruising speeds. I have noticed in other tests of flybridge boats with pod drives that fuel efficiency gains seem to be minimal if any at all over shaftdrive boats. It seems to me that pod drives work better with lighter weight sports cruisers than they do with heavier flybridge boats. It is interesting to note that very few mainstream European builders have yet adopted pod drives for their flybridge boats. Maybe they know something we don't?
I accept that pod drives can give other benefits in terms of releasing more space for accommodation and manouvering capability but their primary benefit was always supposed to be fuel efficiency and in many boats, that just doesn't seem to happen. What does the panel think about this?

 

[MapisM]

their primary benefit was always supposed to be fuel efficiency

Not really, M.
That's the selling point towards us poor boaters, but since VP released its IPS, the real KSP towards builders has always been the faster/easier installation during build (=lower build cost).

 

[volvopaul]

Mike I have yet to hear a true boat owner say that I p s is overall cheaper to run than shafts, also no one yet has bragged off how cheap they are to service, how reliable they are over out drives of plain shafts.

I can tell you the service costs on I p s are horrendous, each drive alone holds 16 litres of oil, 5 litres is just shy of £100 Inc vat, the shaft seals leak just like normal outdrives which then requires the drive removing stripping down to flush out the emulsified oil, along with software problems leading to shutdown, I believe cummins has had problems as well on software front, though I've not seen many sea lines with the pods off yet, then again there not as popular as the Volvo I p s.

If I were buying I'd certainly be factoring in 4 years of proper dealer servicing into my budget.

Your azimuth is far heavier construction than the prestige, and no doubt better built in areas you don't see, but the likes of me do, then suck through teeth when bits are revealed behind panels etc.

The readings given no doubt will be from the cummins smart craft system on board which gives a readout on the dash, playing with throttle setting against speed over ground will give better results on m p g, but of course sea conditions can play havoc against what could be an optimum m p g figure.

I find that heavy flybridges are better with bigger motors that are running under stressed loads rather than small motors revving there nuts off at near wot, where the fuel burn is horrendous.

 

[Deleted User YDKXO]

Your azimuth is far heavier construction than the prestige, and no doubt better built in areas you don't see, but the likes of me do, then suck through teeth when bits are revealed behind panels etc.

Right country, wrong builder VP. It's a Ferretti Interesting info about servicing costs. I think you are right about heavy flybridge boats. The smaller engines fitted in IPS systems have to work a lot harder which probably harms fuel economy

 

[volvopaul]

Right country, wrong builder VP. It's a Ferretti Interesting info about servicing costs. I think you are right about heavy flybridge boats. The smaller engines fitted in IPS systems have to work a lot harder which probably harms fuel economy

Sorry mike so it is, and I've only just got to read your article in the mag, looks great out there cruising, no wonder the mrs didnt like it here any more, it's just pants!

 

[Deleted User YDKXO]

no wonder the mrs didnt like it here any more, it's just pants!

Especially this year!

 

[rafiki_]

Especially this year!

It really is dire in the UK this year. Really considering whether this boating lark is worthwhile. Yes JFM, I'd love to join you in the SofF, however, my work commitments don't make that choice viable at the moment.