1st few trips - is the performance ok?

tanimola · 30 October 2012, 19:46

First chance to put the boat on the water this half term.....

Brig F400S with an etec 40

The plotter was showing 25 Mph at approx 5500 revs - does this seem 'about right'?

willk · 30 October 2012, 20:47

Was the plotter set for Miles or Knots?

Overall, you're in the ballpark though. Did you experiment with engine trim and overall loads (weights)? On a boat this size, extra fuel and passengers and "stuff" make a big difference.

tanimola · 30 October 2012, 21:16

Quote:

Originally Posted by willk

Was the plotter set for Miles or Knots?

Overall, you're in the ballpark though. Did you experiment with engine trim and overall loads (weights)? On a boat this size, extra fuel and passengers and "stuff" make a big difference.

Set to mph, me plus 3 kids, engine trimmed up slightly, boat straight onto the plane and running very smoothly!

What should I expect for 'maximum' speed?

tanimola · 30 October 2012, 21:32

Interested in what sort of fuel consumption I should expect, running at average 10 to 15 mph - thanks

willk · 30 October 2012, 21:36

I don't know how much experience you have, so please excuse the question - did you trim the engine up while running on the plane?

Max speed will only be discovered if you gradually trim up while underway to discover that sweet spot where you get max revs but before the prop starts to ventilate (engine revs wildly). Ditch the sprogs, tidy out the lockers and try it on calm water with a 1/2 tank of gas - that's your top speed with that rig

willk · 30 October 2012, 21:38

Quote:

Originally Posted by tanimola

Interested in what sort of fuel consumption I should expect, running at average 10 to 15 mph - thanks

Very little

That Etec is maybe most efficient around 3000rpm (anyone?)

tanimola · 30 October 2012, 21:39

That's the plan for the spring - are you offering your babysitting services? Thanks

Poly · 30 October 2012, 21:53

Quote:

Originally Posted by tanimola

What should I expect for 'maximum' speed?

A little but not much more than that. Probably lucky to break 30mph.

Quote:

Originally Posted by tanimola

Interested in what sort of fuel consumption I should expect, running at average 10 to 15 mph - thanks

that might not be your best fuel economy. I think you'll probably manage close to 2 miles per litre at cruising speed on a rig that size, but you need to test it to see before relying on that.

Ribochet · 30 October 2012, 22:06

Quote:

Originally Posted by willk

That Etec is maybe most efficient around 3000rpm (anyone?)

Probably more towards 3500 rpm where you would expect a fuel burn of about 1.5 gal/hr

9D280 · 31 October 2012, 17:24

At that sort of speed with my aged 60Hp I drink 0.83L/ Nautical mile = approx 0.96L/statute mile. You should get sligtly better than that with a smaller, lighter boat with a more modern engine.

For cruise planning, 1L/ Nautical mile is a good going in point. (1.2L/statute mile if you prefer working in land units)

As said before, play with the engine trim & weight distribution - you will be amazed at the differnece it makes. (if you got Power trim you will hear the engine change note & at some point it will "sing" as you trim out)

BogMonster · 01 November 2012, 10:21

My 150 E-TEC on a 5.8m usually achieves somewhere about 1.15nm/L (about 1.3 miles/litre) in the cruise which I think is sitting about 3500rpm ish - 26/27 knots is about the sweet spot in economy and I focus more on speed than rpm. So I'd expect a 60 to be much better than that.

9D280 · 01 November 2012, 13:45

1.15 nm/L = 0.86l/nm - Not much worse than mine..... Which is in agreement with the general consensus of loads of prevous threads that it doesn't matter what you got, 1L/nm is a good planning figure!

To put my consumption figures into perspective, since the rebuild and not including my last run, which I have not refilled since so don't have a decent number for fuel-

27 Hours, 229.5nm, 202.5 L at an overall ave speed of 11.54 knts

Of which
10 hrs were at 25:1 at slow speed (running in)
7.5 hrs were at 1500 RPM along a canal (at a spectacular 4 knots - 2L/nm

)
20 miles of slow- ish speed during the Stirling cruise when we were accompanying a lot of displacement craft.

The overall average consumption taking those two unusual events into account drops to 1.04L/nm.

As the Stirling cruise & the running in become smaller proportions of the total, that average creeps down now every time I go out.

Come back to this thread in a year and who knows?

BogMonster · 02 November 2012, 09:35

My old engine (Johnson Faststrike V4 115, carbed 2 stroke) used to use more like 1.2L/nm despite being a smaller engine pushing a lighter boat (5.8 Destroyer). That's 40% more fuel than the E-TEC, and by eck I notice the difference now ... though handily (not) petrol prices have increased by 40% to compensate.

But you're right, anybody working on 1L a mile isn't going to be wildly surprised with most options. Quite bloody expensive, rather bloody expensive or very bloody expensive being the options available for running a boat