Monte Carlo MCY70 fuel consumption

This is from the article;

"If the intention is to really put on some distance, better idle speed of 7.6 kn, the same cruise speed is an average trawler yacht, and she'll burn a combine 4 gph (15.1 lph) and keep going for 237 hours and 48 minutes and 1,799 nautical miles."

When our 80-footer (from Delta Powerboats) was tested, she burned 16 lph at 7,5 knots with a range of 2.250 NM. This is with triple Volvo Penta IPS/1200 running 600 RPM. So the figures for the Monte Carlo 70 seems to be OK and not very low....

Seem reasonable. Keep a couple of things in mind though. That's basically at idle. Go to 1000 rpm and you cut the mileage by 63%. The question is what speed will you actually run it. Until actually testing your engines and your set up I'd be very reluctant to set out on a trip depending on 1500 nm plus. The range drops to 656 nm at 1000 rpm.

Most would be amazed at the range of some pretty large engines get at idle speeds. Just they aren't often run at that speed. A 100' Hatteras with twin 1900 CAT's and conventional drives gets 1.2 nmpg at 600 rpm for a range of 4920 nm. But at 1000 rpm and 10 knots it's only 2057 nm.

I think you should look at it the other way, to make short runs at idling speeds and normally run at "design speed", which is somewhere between 20 and 30 knots...

BT's reviews have become much more comprehensive in recent years, but are clearly weighted toward advertisers, which can be cause for concern. IMO, their coverage could be directed at more worthy recipients.

Perhaps as users we might be more worthy, but we don't pay as well.

BT and PMY and others are heavily positive and designed to remain in the good graces of builders. However, if one goes in knowing that every boat will get a positive review, then they can still get some useful information. You can find out certain features, almost like an expansion of the information on the builder's site. Then the one benefit I do find is the tests. I've found the speeds, the fuel usage and the decibel levels to be beneficial and reasonably accurate. Even within the reviews I've occasionally found useful information. As they write a glowing review, there will sometimes be that one thing they aren't as fond of. Translated that means "I really disliked this aspect."

While I love the reviews here most, often times to gather information on a boat you take any source you can find. Also, the tests are something one has to search for as the vast majority of online reviews do not have tests available.

Basically I'd say reader beware, just as you would if reading on the builder's site. They are not unbiased independent reviews. But a discriminating reader can pick up useful information. Oh and one other thing is that each reviewer has their personal bias's, just as we do. One, for instance, does not like or see the need for lower helms. So he reviewed a model we were looking at and gave it glowing reviews for using that space for a country kitchen. We strongly disliked that. They all have their preferred speeds as well. They might not mesh with yours.

Most boats are designed for a certain purpose, but many can of course be used in different ways. So the short answer is that it is always better for the boat to be used than not used at all. In fact, many fast boats seems to be used in slow motion these days...

Mikkel,
Like you, I to am the proud owner of a mid 20' bowrider that I use to go fast and trailer occasionally to lakes. My choice for a cruising boat was a 50' Californian Veneti from Navigator yacths. While I cruise the Columbia River out of Portland OR and use her for a weekend retreat I do not find that I cruise at planing speed. We prefer the 10-12 knot cruise by far. Noise, traffic is easier to manage, fuel consumption to name a few. Plus we come from a larger sail boat for cruising and 10-12 knots seems quite fast. She will cruise quite happily at 20 knots and WOT 29 knots if we choose which is what drew us to her versus a trawler.

In addition we like the large aft cockpit and swim platform for the dinghy.

She is a 50' pilot house style so no fly bridge to keep clean and like I said we have the bowrider for open air fun in the sun. Besides we keep a 13 foot skiff with a 40 horse that is a blast to launch and zip around on.

While Navigator is out of business there are plenty of similar vessels. Since you have your eye on larger vessels that are not trawlers I would steer you toward the new SeaRay 650L (non fly bridge version).
http://www.searay.com/page.aspx/pageid/160931/L-Class.aspx

Sabre 66 Dirigo:
http://sabreyachts.com/dirigo-66-motoryacht/sabre-66-dirigo-overview

Just to think of a couple of new options.

Have fun!
-Greg

How about Azimut Magellano series? It seems to me it could tick your boxes regarding design...
And another question, can you damage the engines runnig them for longer periods on idle speed? There is a story around here about a guy that went from Dubrovnik to Portorož on idle speed and had to replace/rebuild engines afterwards....

Yes, all in all E rated or pleasure rated diesels are designed to run at cruise speed/ 80% load. Running them at dead idle does result in dirtier cylinders, incomplete combustion and too much fuel which can wash the liners out prematurely as well as carboning up the exhaust ports, turbo's etc. . Modern electronic diesels do a much better job at metering the fuel and such, but running a diesel at dead idle speed for 6 days straight is going to do some damage. I do run them at 1000 rpms for 6 hours, then up to cruise for 30 minutes and this seems to be a good compromise. Granted there are times you're going to stay below 800 rpms for a few days in a yachts life. Having to take the ICW in places, the Erie Canal and on and on......But doing it intentionally at 650 rpm's for pro-longed periods of time is going to create some excessive wear. Also a planing yacht like the Monte Carlo is not going to handle a sea-state very well at 650 rpms...... at 9-10 knots it probably would, but not at 6.5 knots.

You could run them for say 4-6 hours at 650 rpms, we do it all of the time on the ICW where we cannot throw a wake (sometimes longer than that). The problem is, you're not going to maintain good steerage and just wallow around in the ocean. Diesels (2350rpm) get great fuel economy up to 1000 rpms. Personally I wouldn't run them below 800 rpms, but then after 6 hours I would run them at 80% load for 30 mins then back down. 1000 rpms is a good compromise of speed, comfort, and fuel burn most of the time. If you're this concerned about fuel, you're looking at the wrong boat. Perhaps a trawler should be considered or a sailboat.

We often talk about wind and current, but rarely about the force of waves. Waves that are breaking at 2 meters per second are actually 3.9 knots. If you're in wind, current, waves or some combination in a boat that is cutting through them that's one thing. But you're not talking of doing that in a 70' Monte Carlo with a planing hull. At 650 rpm, 6.5 knots you're a bit of a toy being moved around by mother nature. Now you can adjust your autopilot or take the helm and continue at that speed in rough conditions. But it will require more work, get you there much slower, and be less comfortable than 1000 rpm and 10 knots. Our Riva's disavow any knowledge of 6.5 knots or 650 rpm and would very much get tossed around in anything more than 4' at that speed. Really don't track well in perfectly smooth water at that speed, plus the engines are not tuned for it. They'd far prefer 40 knots. Our bigger boats can handle it, but not sure we could as it feels as if you're not moving. They could be adjusted to track decently at that speed, but in any sort of rough conditions then the power of mother nature is almost equal to what you're getting from the engines so you're working more to offset the conditions than to propel the boat. Plus not the way those engines are set up to run. For those speeds need more a small engine, designed for continuous operation and heavy loads. Ours are large engines designed for fast vessels with low load factors. And yes I know a 499,000 lb displacement doesn't sound like it would be low load but it is with 5790 hp. And the Monte Carlo with a 42 ton displacement and 2400 hp would be the same.

When we were looking, one thing we found was that even in larger yachts, the "Euro boats" tended to lack range. Sunseeker, Ferretti, Princess, Monte Carlo and others. It seemed to be displacement and range or semi-displacement and planing without range. And that wasn't just because of the fuel usage, but a great deal of that was simply the size of fuel tanks. Their target seems to be the Mediterranean where the typical user doesn't require that much range.