Displacement hull

[shanemax]

I'm sure it does. All I'm saying is that other factors sometimes come into play, such as the pub closing time.

You are right. A gallon of petrol cost approx £8 but a gallon of beer cost approx
£36 so perhaps being late for the pub is not a bad thing , financially
, but I take your point. Beer tastes better than petrol.

 

[Chiara’s slave]

Submarine Yes good old fashion diesel, no DPF or Exhaust recirculation, no oxygen sensors just a smoky diesel charging lead acid batteries.

I like the other kind.

 

[Shaz77]

I have a merc with dpf and egr. Always a problem

 

[Concerto]

On my Fulmar with a 25hp Beta engine, I usually motor at about 1800 to 2000 rpm as this gives good fuel economy. Upping this to 2200 to 2400 rpm increases the speed by about ½ to ¾ knots, but the fuel economy increases from about 1 litre an hour to about 1¾ litres per hour.

Look at this chart from Beta showing the consumption per hour at different revs (the lower red line).

https://betamarine.co.uk/wp-content/uploads/2020/07/B25-HE-Power-Graph.pdf

You could also improve your fuel economy by having a clean bottom and not towing a dinghy.

 

[Chiara’s slave]

I have a merc with dpf and egr. Always a problem

I daresay it is. Whilst modern diesels are pretty clean, if you wanted to design a low emission vehicle from scratch, you wouldn’t start with a diesel.

 

[Shaz77]

I daresay it is. Whilst modern diesels are pretty clean, if you wanted to design a low emission vehicle from scratch, you wouldn’t start with a diesel.

You are very right. The diesel engine was never designed to be clean. It was designed before emmisions were even thought about.

 

[alan_d]

That sounds fine for flat water, but a current or seaway can change things. Taking a reductio ad absurdum, if you motor at three knots against a three knot stream your fuel consumption becomes infinite. Depending on the prop perhaps, you may find that motoring slowly against wind or waves is very inefficient. I get the impression that my 2-bladed folder 'slips' more at low revs and is sometimes more economical when motoring moderately hard.

 

[justanothersailboat]

Sounds like time for a scrub, to me.