"Flank Speed" engine revs?

[Fergus]

\"Flank Speed\" engine revs?

We did Bembridge - Poole in 6 hours with favourable tide in a flat calm on Sunday - about 2500 revs. She seemed fine at that rate - what's your experience (assuming all diesels have a similar rev range which may not be the case?)

 

[ZuidWester]

Too fast for my old heart

2000 rpm is max for my BMC 1500. Same for alot of diesels I know of (DAF, etc.). Depends on the boat weight aswell. Took a 7.4 meter rib for a run the other week fitted with a Volvo Penta 220 HP diesel. I could push it to nearly 4000 rpm for quite some time without overheat or strange sounds. Bembridge to Poole would be a breeze at that rate!

 

[Swagman]

Re: \"Flank Speed\" engine revs?

That sounds like a good run.

IMHO boat, engine / gearbox and prop all contribute along with weight and design - to motoring efficiency.

We've a 46 footer than possibly displaces not much more than your 32 footer - and 2500 revs with a three bladed maxiprop from a 75 HP turbo'd engine - gives us 7.2 knots.

It is our favoured setting - but we can get up to 3,800 when required.

Cheers
JOHN

 

[DJE]

Re: \"Flank Speed\" engine revs?

Came back across the channel on Sunday with our Volvo 2002 doing 2200rpm all the way. That gives us 6 knots and anymore revs gives a lot more noise.

 

[Rob_Webb]

Re: \"Flank Speed\" engine revs?

Normal cruising around 2200-2500 revs giving 6kts depending on conditions. Fast cruise 3000 revs giveing closer to 6.5-7kts. Flank speed short duration appears to be approx. 3600 revs which gives me just under 8kts in flat water with clean bottom.

 

[Ships_Cat]

Re: \"Flank Speed\" engine revs?

Max engine rated revs are around 2,800 which we only get to without black smoke starting if the bottom and prop are clean (we go 2 years before cleaning). 50 HP, 3 bladed sailboat optimised fixed prop on 12 T loaded.

Bottom clean cruise at 7 knots at around 2,000,2,100 rpm (ie roughly 80% max), can maintain 6 knots at that into most conditions where it is safe to do so ie if sea conditions demand a slower boat speed then revs dropped so normally never exceed 2,200 or so revs.

John