Big diesels at displacement speeds

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asteven221

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Okay, now that we have been stuffed good and proper by the government, we are where we are and I am looking at ways I can justify staying in the boating game. One option is to go at displacement speeds, so is it a myth that big diesel engines i.e. >300hp with turbos fall apart if you run them at say 1300rpm all day instead of 2200rpm? If I am going to commit to runing the boat at displacement speeds, is there anything else that can be done to make it more economical e.g. altering the props or removing the turbos. Any other ideas?
 
I think we are all over reacting. Most boats average around 50/75 hours usage a year. Last year we spent some £700 in diesel, next year it may well cost us £1400/£1500, but in the grand scale of things, an additional £700/800 is, well not exactly a drop in the ocean, but compared to the total of all the other costs, including the money tied up in the boat, and marinas at several £thousands a year etc, it really isn't too bad.

I reckon that once the dust has settled, and we've got the shock out of our systems, we'll all go boating just as before, but perhaps go to "faraway" places a couple of times less in the season.

Don't let the [--word removed--] grind you down!!
 
I al ready know os ome who really struggle to go boating and will have to drop out.
I know of others who will not trade up - I think that effect will ripple through the market and I think the market will be effected.

I know that it will encourage more of the larget boats to stay or go abroad.

I soo it is a critical market event and not something that the market will just absorb.
 
It takes alot of hours before turbos go tits up and there not that expencive to mend.

Cant think Nicho? ever gets out to sea on £700 a year. We can burn that in a couple of weeks!!

It's quite dramatic how much less fuel you burn at six knots. I was up the Severn for about 9 months and did not buy any fuel on the river at all. Used more in the heating than the engines.

Big problem with going slow though, if a planing boat, is rolling. Might soon get fed up of that.
 
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I think we are all over reacting. Most boats average around 50/75 hours usage a year. Last year we spent some £700 in diesel, next year it may well cost us £1400/£1500,

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Blimey how do you get an S41 to use as little as 30 litres an hour , assuming you did 50 hours at an average cost of 45p/litre. Do you go everywhere at 10 knots?
 
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Cant think Nicho? ever gets out to sea on £700 a year. We can burn that in a couple of weeks!!

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I have to confess we did not go that far last year, Weymouth was the furthest, with the vast majority of our trips being from Chichester to various points in the Solent, Lymington, Yarmouth, Cowes etc.

We will still do a West Country cruise and poss CI next year which will burn more, but as retirees, we'll ensure we stay there for goodly amounts of time to get better value.

I'm not going to get too pissed off about it - the last time we counted the ACTUAL cost of boating (including the interest lost on the cash tied up in a boat valued at around £170000), we sold the boat!! The TRUE cost was about £15000 a year:

ie £7000 lost interest, Marina at £6000, Diesel at £850, engine servicing at £1200, antifoul/anodes etc £600 = £15650!!

One year on we saw the error of our ways and returned!! - so, an extra grand on diesel is not perhaps a huge deal when viewed in that way?
 
The figures look a bit different for me, as we actually went somewhere. But back again in the same day, hence the fuel bill.

Boat is an S28 with twin KAD32's

Diesel cost for last year = £1350
Mooring fees = £3300
Servicing & parts = £800 (Grease Monkey Panda doing most of the work)
Insurance = £600
No idea on depreciation, loss of interest on capital, could be £3500 or therabouts.

Bottom line is that the gym membership that we don't use enough is going to have to go. £100/mth * 12 should pay for the increased fuel costs. Sorry, David Lloyd, the victim of the loss of Red Diesel is YOU.

dv.
 
A 34ft boat or thereabouts would have been nice, but now, no way! 28ft is as big as it gets, excluding Premium Bond and Lottery results.

dv.
 
An S34 with the same engines wouldn't use any more, but a top speed of 29kts isn't good enough! I'm talking something with errm, twin KAD43's?

£1350 at 50p/litre is 2700l.

Hours (before gauges packed up due to moisture) = 100

So, about 27L/hr for both engines, which isn't bad, although some of that would have been at trundle speed. Planing speed is probably 35-40L/hr.

Point is, there are other pressures on my finances other than boating. I could sell the wife, put the 2yr old into the workhouse, or (last resort) drive a slower car, but it's about how much I'm prepared to sacrifice. That stupid gym membership is easy to give up. The next one will be much harder.

dv.
 
I am not quite with this thread, but correct me if I am wrong, any turbo'd intercooled marine engine is happy at 200 revs below max, our Sabre 180's based on 1976 Fords, yes 1976! develop max at 2500 and we are doing 19 knots (downhill), and burning about 8 gallons an hour, so in theory we should do about 22 miles in that hour, if we slow down to displacement speed 10/11 knots and then get the fuel consumption down to say 4 gallons an hour we will take twice as long to get were we want to be and burn the same amount,yes or no?
 
I was getting out of my pram over this red diesel thing, not so much for the fuel costs but for the devaluation of the boat. Have I got it all wrong? No one seems to be worried about that, so maybe I was concerned for nothing.

When I was looking at boats, petrol ones were a lot cheaper, I assumed mine was now worth no more than a petrol version. Which for me would be about £10k less.
 
>if we slow down to displacement speed 10/11 knots and then get the fuel consumption down to say 4 gallons an hour we will take twice as long to get were we want to be and burn the same amount,yes or no?

If those are the stats, then yes.

To get most planing hulls working more efficiently than planing speed, you have to be going REALLY slowly. Like 6 kts. Not 10-11kts.

dv.
 
Can't see it - diesel boats in the Med aren't much cheaper cos diesel price = petrol price. One group of people to suffer will be those doing petrol to diesel conversions. Although I still want diesels in my boat, the group wanting to convert solely cos of lower fuel costs will shrink dramatically.

I still prefer diesels due to the better mid range torque, no ignition system to go wrong, freshwater cooling (yes i know petrols can be fwc, but hardly any are) and better economy.

dv.
 
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[Diesel at £850, engine servicing at £1200, ] /forums/images/graemlins/blush.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

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And Cherbourg in three and a half hours! I've done the sailing bit remember?!
 
We did half of last year with an S37, the rest with S41. However for a variety of reasons we did not achieve average hours, hence not so much spent on fuel. Our S41 on KAD 300's does around 19/20 gph at 24kt cruise (3200rpm), or 90 litres per hour.
 
A modern displacement cat is usually very efficient at around 15 knots compared to displacmeent mono at around 8/9 knots. The FP performance figures are shown in article to be 2.7 gals per hour at 12 knots. A planing mono hull like a sealine is usually very inefficient at displacement speeds. Sadly, it does not give performance figures of F34 in the article. Anyone know what consumption of F34 at 12 knots would be for general comparison?
 
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