Top Trumps (?!) - Performance figures for Regal 1950, Sealine 260 and Merry Fisher 625

C

CrawfW

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Hi,

After uncountable hours looking at adverts and posts on here, I am trying to pin down numbers for three similar-but-different types of boat: a Sports Cuddy, Sports Cruiser, Pilothouse.

The use-profile would be outings around Lyme Bay and – more occasionally – weekends in the upper reaches of the Dart. Probably based on the Exe, but that is TBC.

I hope the figures for each of them is broadly representative of a type – and i appreciate that their accommodation is very different -

1. Regal 1950 (10K and 5.94 m long) which has a top speed of 40 knots. It cruises at 25 knots using 10 lph from 190 hp.​
Draft of 0.79.​
​
2. Sealine 260 Senator (25K and 8.5 m long), which has a top speed of 30 knots. It cruises at 20 knots using 20 lph from 300 hp.​
Draft of 0.86 m.​
​
3. Merry Fisher 625 HB (20K and 6.4 m long), which has a top speed of (almost?) 30 knots. It cruises at 18 knots using about 18 lph with a 115 hp outboard.​
Draft of 0.4 m.​

Any owners or experts care to tell me if I am way off?! I am hoping to understand these numbers first, then move onto difference in sea-keeping.....

C
 
What engine does the sealine have? I've got a mag 350 (300hp) in a 8m boat, I use a lot more fuel than 20lph! Probably around about 35 lph or so although I've never really calculated it.
 
CrawfW said:
Wow, still new to this but my most unpopular thread so-far!
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Probably because you are looking at this all wrong. Buying a boat based on figures is almost a guarantee of disaster. How about I throw in a small inflatable tender RIB into the mix. It's figures would average out the winner. Choose based on what you want out of a boat and go from there.
 
I use 30 litres/hr cruising at 18 knots. Boat is 6.9 metres long, around 2.2 tons all up before adding people. 200hp verado outboard.

Up the speed and I can trough around 85 litres/hr if desired!!!

Don't worry abut the fuel consumption. Just allow an average of perhaps £100 per day you are out in it. The mooring and maintenance costs will outweigh fuel costs......
 
stelican said:
If you are trying to compare like for like size wise you should consider the Regal 2250 cuddy, The 1950 is also too small for the boating plan you mention.
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I recently drove a 2250 fitted with Volvo D3 that had been tweaked to 190hp. Very "well planted" boat as far as handling concerned. Depends what your budget is of course!
 
PDF said:
What engine does the sealine have? I've got a mag 350 (300hp) in a 8m boat, I use a lot more fuel than 20lph! Probably around about 35 lph or so although I've never really calculated it.
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They are Volvo Penta 250s, which are 4 cylinder 2.5 litres and 150 HP each. Whilst yours is a V8, your fuel usage seems more like i would have expected....
 
Bouba said:
For the MF i would be looking for 150hp
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Haven't seen one with this size of engine - more commonly 90HP. Have found chat on forums about maximum weights for the transom, but this seems to vary across the sub-models with no-one terribly sure. Of course, i don't see myself buying a new outboard - just the best existing combo i can get.
 
CrawfW said:
They are Volvo Penta 250s, which are 4 cylinder 2.5 litres and 150 HP each. Whilst yours is a V8, your fuel usage seems more like i would have expected....
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And seems to match with this post, saying they will "probably" use 30-43 litres per hour each: volvo penta 250A

Strongly suggests that the broker's claims were a little optimistic!
 
Another way to look at things is that I have calculated my MPG at 3 on a recent 50 mile round trip to the needles......

I use the smartcraft fuel flow system to work out figures..
 
To me the boats in question are too different to compare, unless you apply different requirements or scores for each.
I/O drive vs. outboard would put them into different segments re. maintenance costs.

In the event of removing/replacing the engine, the outboard is bolt-off/bolt-on. Def. not so for in/out-boards.

The MF 625 is for 115 hp max and with the rule of thumb to not go below some 80% of max, 90 is a common choice. Even though some claim that size doesn't matter, I'd suggest the largest engine you can afford. The MF 625 is 950 kg. Add a couple of persons, fuel, lunch packs and beverages + an engine and the vessel GW is some 1500 kg. 115 hp pushing that weight on a modified V-hull calculates to max. speed of ~32 knots. The MF will do this in comfort on calm waters only.

For fuel consumption you in literally have to feed the number of horses you put to work. To move a given weight at a given speed you'd need a certain amount of hp. Hence you have to serve juice equalling the hp you demand from your 'horses' (engine).
Interestingly, if demanding eg. 100 hp it normally will be more economical from a 150 hp at modest throttle than a 100 hp running flat out.

Best MPG usually is at hull speed (the speed at which the wavelength of a vessel's bow wave is equal to the waterline length of the vessel) calculated as
v_{{hull}}\approx 1.34\times {\sqrt {L_{{WL}}}}
where Vhull is the hull speed and LWL is the waterline length.

For planing boats, best cruising MPG normally is at the lowest speed where it remains on stable planing. Often achieved by running at full throttle until planing, then reduce throttle until the sweet point. Boat design decides if that speed is usable at the actual state of sea and weather.

Calculating backwards you'll see that a lighter boat at a lower speed returns the best MPG. If it then provide the facilities and ride you want is a different matter.

The actual comsumption for any boat is decided at the helm. "Push the throttle and pay" -philosophy.
On the upside only engine hours need fuel so for the time spent at anchor or in marinas, the fuel consumption is zero. Might be diffferent for the crew ?
 
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ChromeDome said:
Best MPG usually is at hull speed (the speed at which the wavelength of a vessel's bow wave is equal to the waterline length of the vessel) calculated as
v_{{hull}}\approx 1.34\times {\sqrt {L_{{WL}}}}
where Vhull is the hull speed and LWL is the waterline length.
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What a load of tosh. It's all very well working out your fuel consumption to the nearest litre but that assumes perfect conditions. How much are you going to use when you have to head home against tide or against a nose wind or you have to motor in a heavy sea. Agreed fuel consumption is a factor but if you like a boat and it ticks all the boxes just go for it and have fun. After all, we all do this for fun. If I was worried about how much fuel I used everytime I wanted to go out, I wouldn't leave the marina.
 
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