Fuel Economy of 26X with original Honda BF50 4 stroke?

[Drifter]

A search for fuel economy gives over 500 hits but I was getting lost in there, so back to basics...

I am getting a 26X from 1996, with its original Honda BF50.

I'm presuming it's carbed, not fuel injection at that age?

With just 4 people and a cooler, can anyone guide me on expected fuel consumption, at:

• Hull speed (and what is the hull speed on a 26ft yacht?)
  Minimum planing speed (and what is that?)
  WOT?

With and without ballast?

I guess currents and wind make a big difference (and using the sails would help...) so I'm thinking in terms of gallons or liters per hour kind of thing?

I'm super-duper confident it's going to be a lot more economical than my current 30 year old Evinrude V6 2 stroke 200 HP, but just how much more economical?

If anything the Mac is bigger than my current 23ft speedboat

[kurz]

I SAY:
5KN... 2.5l / h, nearly same if ballast or not
6.5kn... 5l.... Hull speeed
Foll throttle.... 18l....

[Drifter]

That's the kind of data I needed, thanks!

So a bit below hull speed is much more economical? Interesting, and certainly worth knowing.

[Herschel]

It has been a long time since I had my carbureted '98 Mercury on my X (have a Yamaha fuel injected now), but generally, with a pretty heavily loaded boat with bottom paint, I needed about 8 knots to be up on plane and steaming smoothly toward my destination. My memory is that I was, generally, getting about a mile per liter (3.3 miles per gallon) at that speed in a relatively flat river at sea level no ballast. Very rough calculation from a very questionable memory.

[Drifter]

More useful data!

I'm feeling smarter already.

My does have bottom paint. Doesn't really need it as I'll be using a trailer but the current paint looks pretty blistered and nasty, so I don't fancy trying to get it silky-smooth and white again

[opie]

from a 2009 thread.......

On our last trip, 161 NM from Wrightsville Beach to Charleston in the ICW, we ran at 5200 RPM, we had trip segments of 3.62, 4.21, 4.24, and 4.29 nm/gallon. Our speed avg was 9.97, 10.75, 9.6 and 9.14 nm/hour.

viewtopic.php?f=9&t=13526&hilit=gas#p156526

[Herschel]

More useful data!

I'm feeling smarter already.

My does have bottom paint. Doesn't really need it as I'll be using a trailer but the current paint looks pretty blistered and nasty, so I don't fancy trying to get it silky-smooth and white again

Are you really in Borneo? Just curious; never had the pleasure of knowing anyone from there. Sailed the South China Sea a bunch in the 60's...courtesy of several all expenses paid cruises on Uncle Sam's Navy ships.

[Drifter]

I'm from the UK but I have lived here for the past 15 years or so.

I find it more civilised than England

Was the other way around I'm sure, back in the 60s...

[Herschel]

I'm from the UK but I have lived here for the past 15 years or so.

I find it more civilised than England

Was the other way around I'm sure, back in the 60s...

Interesting. Curious about wildlife that you need to be mindful of in Borneo while sailing and boating. We have to be on the watch for alligators that might want to make a meal of dogs that might be wading around the boat when pulled up on a beach in my river. We are, also, careful about where and when we swim. Snakes are common. And, of course, the pesky racoons are always ready to inspect one's garbage if left handy. I bet your fauna is quite varied!

[Drifter]

The salt water crocodiles here make alligators seem cuddly and friendly! Every bit as big and nasty as anything in Australia, they're seriously powerful animals that are not even slightly intimidated by boats.

Snakes are less of an issue as even the very deadly types will prefer to avoid you, so just making plenty of noise is usually enough. Since I've been here I've only known 2 people get bitten, 1 did die sadly while the other 1 just spent a few inconvenient days in a hospital far from home (hiking about 180 miles from here).

Lightning is probably my biggest fear here, as a thunderstorm in the afternoon is pretty much expected.

Every day.

In fairness probably only once a week but weather forecasts are identical every single day - "hot, humid, broken clouds, chance of a thunderstorm in the afternoon"

Hence my plan is to set off early chasing a retreating tide with the sails, head around 30km off the coast for some fishing for about an hour then lower the sails and mast, up the boards and rudder, empty the ballast and motor back.

That would be a whole day I think, around 10 hours or so, but knowing the Mac is capable of getting back in 2 hours if necessary, and always willing to turn back early if a thunderstorm is coming early...

[NiceAft]

First: Are you certain that your Honda 50 4 stroke is 24 years old? It’s entirely possible that since 1996, a new motor was purchased.

I have a 2003 Honda 50 4 strike on my 2005 . The conditions you sail in make it hard for a comparison of fuel consumption or speed to be made. You go in open ocean, with all of the currents and swells to effect both fuel consumption and speed. I believe the responders to your post, go on lakes and rivers, at least most of the times, so take that into consideration.

Second: Change your mind about it being OK to empty your ballast while motoring home from 30 kilometers at sea. That ballast should be full at all times. These Mac’s are self righting; do you really want to test this, especially with some of those sea going crocs smacking their lips.

[Drifter]

My aim is to keep the ballast full and take it real easy, but my understanding is that for full-throttle run-away-speed (tm) one should empty the ballast and throw passengers overboard?

That's the plan anyway

Certainly if the sea conditions get rough I''d rather be ballasted and slow; I'm thinking more about swiftly covering most of the distance when practical, so I can relax a bit.

Don't think i'd enjoy a slow sail back while watching the clouds gathering! I'd rather have all 50 horses ready and willing.

From what I've read it seems the efficiency is enough that I could actually motor out and motor back again, on a single tank and maybe a spare can if keeping it real slow. Or sail out and 80% throttle on the way back.

I hear a lot about how it's not an ocean-going yacht and I accept that. Thing is, by local standards it's impossibly safe... A self-righting boat? A self-baling cockpit? That doesn't sink even when swamped? That can sail home even if the engine is totally dead? That can be hand-started if the battery dies? NONE of those apply to my current boat, which relies on burning 140 liters of fuel and blasting you to and from at ludicrously high speed, with instant sinking if you stuff it up.

Same with most local boats, they are basically open tubs and sink like a brick with one big wave over the stern or side, yet locals take them 50 km off shore. And there's no real coast guard here, no tow service, EIRBs are likely to be ignored, so I'm being conservative and saying 30 km max

Regarding the Honda, it looks pretty old and my understanding is the seller is the original owner from new and everything is original, so yeah, the engine too I guess.

[NiceAft]

There is nothing to stop you from sailing with the motor running at 1000 rpms.

As to the ballast, with your fifty HP, ballast in, full throttle, you may get 16KPH (a guestimate). Without ballast, 22 KPH (again, a guestimate). My guess is that on the open ocean, you will never feel comfortable at 22 KPH. Full ballast at 16 KPH may end up being the choice.

Hull speed on the is 9.6 KPH. I would think that in the , it would be similar. The is not as flat bottom as the , so there may be a slight difference.

[Be Free]

A 1996 BF50A is/was carbureted. In general, a 4 stroke gasoline engine will burn .5 lbs of fuel per unit of horsepower when running at peak horsepower (around full throttle for this engine). The RPM/horsepower curve is not exactly a straight line, but if you assume that 1/2 full throttle is developing 25 horsepower on this engine you won't underestimate your fuel burn rate. You are not going to get this boat completely on a plane where the fuel economy will improve. Somewhere just below hull speed is going to be your sweet spot. Anything which increases drag (heavily loaded, foul hull, adverse wind/waves) will move that sweet spot lower.

Conversion to SI units is left as an exercise for the interested.

[Drifter]

"Motor sailing", with the engine giving a bit of a nudge does actually sound about perfect for an enjoyable day out, where I can fiddle with the sails and do the whole pirate thing, while maintaining at least some forward momentum

Could be a good way to learn how to get the best out of the sails, while more forgiving than sails alone is what I'm thinking. I'd certainly like to experiment with that, always mindful that the designer basically says not to do so beyond walking speed really.

Thing is i don't have the boat yet, so really can't say if i'll enjoy the sailing as much as i think I will? It also depends upon the local conditions here. Normally i'm blasting past with a cloud of 2-smoke behind me, and I really don't know if my patch of the South China Sea is a sailor's paradise or totally hopeless. Never really looked at it from a sailing point of view, yet fell in love with the That interior space is incredible for a vessel only ft longer than my current beast, and yet it's also a dual-purpose sailing/motoring package.

Just an incredible, crazy design and I guess I'm the perfect buyer, someone who has got high speed out of my system and wants to experiment with slow cruising, the romance of sailing and making it more of a social event, where the journey is appreciated for its own sake with some good company, rather than something to be got over and done with.

who knows, maybe I'll enjoy the sailing more than the fishing?

OK, that's very unlikely but possible I guess. Or maybe I'll hate it and just motor everywhere, even leave the mast at home. It'll still be a fantastic boat compared to anything else around here, with vastly greater safety features, social features, comfort features and so on.

But yeah, looking forward to at least trying to sail. When (if!) it arrives, it's going to take me some time to just figure out what ropey things go where and what for.

Are there any actual pics or diagrams showing where the lines and controls are, what does what? I've been playing around on a sailing simulator but that has 4 winches and little locking things that I don't see on the (and I don't see the boom control thingy on my boat at all? I only have a few photos of it).

I talk too much, sorry

Regarding getting it on plane, I'm frankly shocked it even approaches it with 50 HP. I have a 19ft boat with 90 HP and that thing was slow and guzzled fuel. My current boat is a lot bigger but vastly more lively with its 200 HP. If the Mac can equal my old 19 ft boat without the ludicrous fuel consumption I'll be happy.