Fuel consumption: sail/motor. are you serious?!

[mvweebles]

As an update to this resuscitated thread, Weebles, a 1970 Willard 36 trawler with 75hp Perkins 4.236, is currently in Chiapas MX, about 15 miles from Guatemala. We've cruised about 2500 nms since leaving Ensenada last October. We've averaged just under 6.5 kts and burned approx 500 gals of diesel and two oil changes.

As an observation topics such sail vs power; and fuel consumption are popular on forums but rarely come up in real life in anchorages frequented by cruisers and such. At least the ones we've visited.

[TXviking]

Originally Posted by Statistical

Why would you ask ChatGPT for anything. The numbers are almost certainly wrong and comparing apples to oranges picked randomly and just thrown together.

Still generally speaking most motor yachts are fast. Fast boats require a lot of fuel. Big boats require a lot of fuel. Big fast boats require a crazy amount of fuel. Keep in mind drag for displacement hulls (or planing hulls below planing speed) increases by the cube of velocity. Going twice as fast doesn't require 2x the power it requires 2^3 = 8x the power. 8x the power means 8x the fuel.

Planing hulls get more efficient at high speed so they break that cube rule but since they are high speed more efficient or not they still use quite a lot of fuel. The downside also is that planing hulls are rather inefficient at low speeds.

If you want a motorboat that is big & slow and thus lower fuel consumptions look into trawlers. 40" trawler going 7 knots will use about 2 gallons an hour and half that at 5 knots. That is just a rough estimate there are countless variations but it puts you in the ballpark. There is a forum dedicated to them:
https://www.trawlerforum.com/forums/

Not OP, but this was useful to me. 2 gallons an hour is incredibly LOW, and sounds perfect for just cruising up and down the intracoastal.

[mvweebles]

Originally Posted by TXviking

Not OP, but this was useful to me. 2 gallons an hour is incredibly LOW, and sounds perfect for just cruising up and down the intracoastal.

2-gph is on the high side for a 40-foot boat at 7-kts. A few years ago, I went from Long Beach CA to La Paz MX (>1000 nms) on a 40-foot Willard and burned exactly 1.5 gph. My Willard 36 burns just over 1 gph at 6.5 kts. A sistership went from Newport Beach CA to Hawaii and burned 335 gals (0.9 gph) at 6-kts.

[Cheechako]

Originally Posted by TXviking

Not OP, but this was useful to me. 2 gallons an hour is incredibly LOW, and sounds perfect for just cruising up and down the intracoastal.

The 44 ft sailboat in my avatar burned about 3/4 gallon an hour at 7.5-8 knots. Flat water. The hourly usage for the entire time I had the boat was .65 gallons per hour, I kept a log. 51 HP. roughly 10.5 miles per gallon.

I had a little 31 ft Trawler for a while, it burned about 1.25 gallon an hour at 7 knots. It had a fairly big engine for the boat size , 80HP in it. 5.6 miles per gallon

While working building planing boats and testing them, a 26 footer with 250 hp outboard would burn roughly 13-13.5 gallons an hour at 33 knots. 2.5 miles per gallon.

[TXviking]

Originally Posted by mvweebles

2-gph is on the high side for a 40-foot boat at 7-kts. A few years ago, I went from Long Beach CA to La Paz MX (>1000 nms) on a 40-foot Willard and burned exactly 1.5 gph. My Willard 36 burns just over 1 gph at 6.5 kts. A sistership went from Newport Beach CA to Hawaii and burned 335 gals (0.9 gph) at 6-kts.
Attachment 290211

Nice. I'd been worried about getting into boating in part because of the costs. I realize there's maintenance and insurance and all these other costs, but at least the fuel bill doesn't sound nearly as scary as I'd imagined.

I am definitely leaning in the direction of a trawler with an inboard diesel.

[Cargile]

Originally Posted by capn_billl

motorboats suck fuel. No question.

My Searay used 200 gallons US to go 250 miles.

Yeah but what a POSH ride. If you have to ask "how much?" you can't afford it.

[rslifkin]

In general, the guideline is that going slow is fairly efficient, power or sail. And you can allow a bit of extra fuel for a powerboat as you don't have sails and rigging to maintain. It's when you want to go fast that things start getting very expensive (more expensive engines to maintain, much more fuel, etc.).

[mvweebles]

Originally Posted by TXviking

Nice. I'd been worried about getting into boating in part because of the costs. I realize there's maintenance and insurance and all these other costs, but at least the fuel bill doesn't sound nearly as scary as I'd imagined.

I am definitely leaning in the direction of a trawler with an inboard diesel.

I know of three circumnaigators who went from sail to power and did lengthy cruising under power (Alaska to Maine via Panama Canal, 7-years in Caribbean, etc.). All three say the long term ownership costs are about the same between power and sail (have you priced sails and running/standing rigging lately?). That said, sail can be done on the ultra-cheap easier than power. And if you want to cross oceans, it's less expensive to find a capable sailboat than a capable powerboat. We're currently halfway through our cruise from California to Florida on our trawler. I doubt there's much difference in overall costs between us and the many, many sailors we meet.

Regardless of how you chose to go, if there is a desire to cruise, important part is to go.

[Cargile]

[QUOTE=TXviking;3902093] "Nice. I'd been worried about getting into boating in part because of the costs........"

Boating to me is a hobby, a recreation. If I worried about the cost of my hobby I would find another one or take up reading.

[davil]

[QUOTE=Cargile;3903107]

Originally Posted by TXviking

"Nice. I'd been worried about getting into boating in part because of the costs........"

Boating to me is a hobby, a recreation. If I worried about the cost of my hobby I would find another one or take up reading.

[rslifkin]

[QUOTE=Cargile;3903107]

Originally Posted by TXviking

"Nice. I'd been worried about getting into boating in part because of the costs........"

Boating to me is a hobby, a recreation. If I worried about the cost of my hobby I would find another one or take up reading.

That's a good way to think of it, although if money is limited then keeping the costs of a hobby down means you get to do more of it before running out of budget.

[sailingharry]

[QUOTE=rslifkin;3903131]

Originally Posted by Cargile

That's a good way to think of it, although if money is limited then keeping the costs of a hobby down means you get to do more of it before running out of budget.

That is an often overlooked point in many discussions here. The sentiment often is "if you can't afford the (usually premium) version of X, then you really shouldn't own a boat." I have a rather nice, and rather pricey, boat. But I've spent my life making value decisions on EVERYTHING. If I am buying something, be it $50 or $5000, I take a long hard look at the various options, prices, quality level, sources, etc. If I didn't, I wouldn't be able to own and maintain this boat! I would still be sailing (my budget isn't THAT tight), but not in the same style/comfort. When I motor, especially any distance, dropping 1/2 kt drops the fuel bill by what, 20%? It all adds up.

[Johan Leopard51]

Hell, following the conversation / argument if we had one measure such as nautical mile liter instead of five different fool consumption indicators would be simpler. Please avoid gallons because that also differs.

We’ve cruised tropical in sail catamaran and power catamaran, so call it a comfortable 4 couple vessel. Obviously a boat for two will have different outcomes much like a motorbike vs SUV comparison.

Shocker : on a 400nm trip, the 61 foot sailing cat sticking to about 6 to 7 knots (motor assist when needed) returned 50% more fool consumption than a 51 foot power cat. If I raced around at 25 knots the power cat would be horrific fool consumption and the trip would be over inhalf the time, which is not the objective.

Horses for courses. Off the South African SE coast there is a lof wind and wind farms so there a sail boat would ¾ the time be tempering sails and running very good speeds but at low comfort. This ocean snaps ore carriers. On holiday I don’t want discomfort for the passengers and that invariably means a sail boat in nice weather spends most of its time with motor assist. 9/10 of the charter cats in seychelles are under power not sail.

Which brings up whether sail cats generally have very poor motor / gearbox / prop designs because they do REALLY seem to suck far more fool for even a moderate speed than a power cat with two large motors. At 6-7 knots neither is on plane so that is not a debate. So does the answer lie in a sail cat with “proper” motors that you use sensibly?

[TXviking]

[QUOTE=Cargile;3903107]

Originally Posted by TXviking

"Nice. I'd been worried about getting into boating in part because of the costs........"

Boating to me is a hobby, a recreation. If I worried about the cost of my hobby I would find another one or take up reading.

Like anything, there's a budget. I'm not Jeff Bezos, so buying myself a multi-million-dollar super yacht is out of the question. But a used trawler is not. Somewhere in there, operating costs also come into play. The forum is helping me get a handle on what I can afford.

It must be nice to not have to worry about money for your hobby, but I'm not quite there yet.

[Tillikum]

Originally Posted by mvweebles

As an update to this resuscitated thread, Weebles, a 1970 Willard 36 trawler with 75hp Perkins 4.236, is currently in Chiapas MX, about 15 miles from Guatemala. We've cruised about 2500 nms since leaving Ensenada last October. We've averaged just under 6.5 kts and burned approx 500 gals of diesel and two oil changes.

As an observation topics such sail vs power; and fuel consumption are popular on forums but rarely come up in real life in anchorages frequented by cruisers and such. At least the ones we've visited.

I'd suggest you consider a centrifugal oil cleaner such as the Spinner II. Oil under regular usage does not "wear out" and you will save yourself a good deal of money, mess and time, as well as considerably extending the life of your engine. Personally I would plumb the unit so you can also use it to clean your fuel with an auxiliary pump. Diesel fuel in some places and some tanks can be very dirty indeed and that dirt will over time damage your injector nozzles, which if they fail can very quickly damage your engine quite severely. This is standard practice on large commercial ships and had been for nigh on a century or so. One caveat is to ensure your engine's oil pump has sufficient capacity to maintain pressure while pushing the oil through the centrifuge, particularly if that pressure also drives the rotation of the rotor in the centrifuge. You will be amazed how clean these units can make even diesel engine oil. Something like 80% of engine wear is caused by particulates that pass right through full flow paper filters.