Going on a multi day cruising & looking for advice

jason

Hello all,

We are going on our first multi day cruise this summer and I am having a heck of a time trying to figure out what to expect from my boat.  I am curious about things like, how long can I count on the fridge when not on shore power.  Do the batteries charge off of the running engine?  If so, how long does it take?  If I'm not in a hurry, is it more fuel efficient to amble along at just above idle, or do I get better mileage from running at best cruising speed on plane?

I hope these questions don't seem too stupid.  I would appreciate any insight, suggestions, warnings etc, anyone might care to share.

Regards,
Jason

OldDogNewTrix

Tell us some details about your boat, model, engines, battery configuration, etc... And you'll get some helpfull answers. Welcome to the forum!

Hamdog

Jason,

Yes, your batteries charge off a running engine just like your car. Actually, that is a pretty good way to charge them. On plane but at your slowest speed to maintain plane is your most fuel efficient way to travel. As for your frig, I can be out two night without a problem but I run my generator say every morning for about 30 minutes to maintain the charge,

Hope this helps and welcome aboard.

Black_Diamond

For fuel consumption: there are two points of being 'efficient': basically idle and then at cruise / on plane.  You might even find GPH vs MPH curves out there from a boat test.  It is interesting to plot out if you have a fuel flow meter, the GPH can really deviate from the MPH at high speeds...meaning much higher fuel use for little MPH gain, same thing between idle and on plane too. 

l-skynyrd

Just my 2 cents....It's all about time verses money. If you have the time go 10 mph. If you want to cut the time to a third than go 30 mph, and pay the price for burning more gas. The boat test web site will give you a good idea of fuel burn at different speeds. If they don't have your exact boat find one same engine and size of a different maker, results should close to your boat.

Hope this helps.....

Len

JoeStang

So you can see you only lose 6 miles of range going from 6.7mph -> 32.8mph. Thats a no-brainer, IMO. Slow cruising is fine in no-wake zones or scenic areas, but IMO I'd rather get somewhere and then take a nap instead of plodding along at 5 or 10 mph for hours on end.

Also think about how many more hours you'll log on the hour meter.

That test is on a FV 250 w/350 Mag. If you have the 5.0 I'd say the figures will be close, but the mph may be a little less for each rpm range.

TikiHut2

Thanks for the chart JS,

NMPG nearly identical at 1500rpm and 4000rpm. I have two separate fuel flow meters on our Merc 350 and our 270 that's loaded for a weekend gets about 2mpg in neutral sea conditions at 3.8 - 4k rpm running 28mph.

Hadn't really done the math on the extra run time at 1500 rpm compared to a well trimmed cruising speed with far less engine time. Always estimated it was pretty close to using the same amount of fuel to go a particular distance but now I know it's relatively equal.

The Admiral prefers a casual pace but I get tired of endlessly correcting for drift even when it's just a bit. We leave for a week of running down the SW Fl coast next weekend and I'll be looking forward to some cruising speed and a stiff drink at the dock rather than hours of cocktail free trawler speed.

When we prep our 270 it'll be for a mix of anchoring overnight in quiet solitude and nights at marinas to hit the pool and out to dinner. I do a float plan for a land based contact and google earth my anchorages of choice. Active captain is a great resource to check on marinas and navigation updates too.

I'll prep all the systems for reliability and we use a large cooler with block ice for food/beverages.

Basically try to unplug, have fun and be safe..... and post some pics when you get back. Mike

Black_Diamond

Just ran about 45 miles @ 30mph (gps). 50 gallons.

Black_Diamond

HF?

JoeStang

I'm guessing, Holy Intercourse?

Spending money on gas for the boat is one of the best things I can think about doing. It means you're on the water and enjoying it.

I just filled up for the 1st time, it'll be an awesome $300.

Lifes Good

HF = having fun!
The original questions above are the most common yet most complicated to answer. Size of boat, power plant(s), gear all change the equation. Then add wind and currents and things get complicated quickly. Here is a general rule of thumb for express gas cruisers 29 to 34 feet. Twin engine. 2 mpg to 1.5 mpg from idle to 1800 rpm. Ie 3 mph to 10 mph No plane. 11 mph to 25ish mph mpg sucks. Maybe on plane but sucks... .75mpg at best. 28 mph to 32 mph is the sweet spot.... or no more than 3950 rpm.... 1.0 to 1.7 mpg depending on size and weight as mentioned above. Over that and mpg suck again. Now if you have say 5.7 vs 5.0 your burn is much better. Less power used (slightly lower rpm) but more torque on 5.7 = much better fuel burn. Up to 0.25 mpg better than 5.0.

If you are running single engine and 26 feet or less you can figure doubling fuel mileage as mentioned above as a general rule.

Numbers based on Floscan history of my boat and 3 other friends boats of simular size ranges. 27 to 34 feet.

LG

LaRea

And the answer is: the ideal cruise speed is determined by sea conditions, not fuel economy.  

Other things to think about for your trip:

Navigation - is your chartplotter up to the task?  Plan your route in detail.  Do you need to seek local knowledge of any tricky inlets, busy shipping channels or shallow areas?  Do you have paper charts as backup?

Write a float plan and send it to somebody you trust.  Stay in touch with them while you are out.

Spare parts - check your stores of filters, belts, fluids, impellers and the tools to install them.

Weights and balances - if your boat is running with the bow too high, try temporarily relocating that 300-pound beer cooler from the swim platform to the V-berth while cruising.  

After you finish loading the boat with all of your stuff, half of the stuff should get put back in the car before you leave.

Enjoy your cruise!

Black_Diamond

Good comments LaRea. Esp the 50% back in the car.

frenchship

Here is some good Infos on fuel consumption .... http://www.boat-fuel-economy.com/mercury-mercruiser-5.0-305-260-fuel-consumption-us-gallons

brianluck

RY those figures are why my boating consists of an average 8 miles round trip. Farthest distance 20 miles round trip. I try to keep my weekends under $100 in fuel

Black_Diamond

We do 1-2 longer cruises a season, Benton Hbr this weekend. Mackinaw Is in july, the latter will be ~500 miles r/t. Bonus this weekend: I'll be at Kate Upton's sister's wedding.