Time to slow things down?

Bob&Jilly said:
This post is interesting, depending on tides and current on the Columbia at 10 to 12 MPH we get about 2 to 4 per mpg with our 300HP Suzuki Outboard on our R-27- even better if we slow down to 8MPH.
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Dry weight of 8,200 lbs for an R27, 10,500 for an R29S. That's a 28% difference, a big factor at hull speeds.
 
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BOSCBIJI said:
Our new R29 burns at 1.6 miles per gallon at anything above about 15 MPH...if we pull down to 8-9 MPH, our mileage goes up to 4.5 or so.

Our favorite destination is (rounding) 10 miles away which means the trip either takes 30 minutes and costs us $40 in gas or we take 70 minutes and it costs us $14 in gas.

Time = Money
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Our 2025 R29CB mirrors this. We have the D4-320
 
This is how I do it. After engine warms up to temp, I will go wide open for a bit to check systems etc. I like to cruise about 7-8 knots. Occasionally, I will bump the throttle up or down 50-100 RPM to give the engine some variety. It purrs like a happy kitten. When the day is over I will also go wide open for a bit to "blow the carbon out" as they say.
 
I just try to think of the airline miles I earn on the credit card when filling up the boat as a "hedge" of sorts against the cost of plane tickets due to rising jet fuel prices instead of realizing what it actually costs to put 150 gallons of gasoline in the boat every few weeks. We see around 1.15-1.20 mpg at cruise (28 kts) and are looking forward to more fuel economy at slightly less stressful speeds with the 5 blade props coming soon.
 
Everybody's talking about fuel prices. The Marinas don't charge road taxes nor carbon taxes, yeah they are high, and don't buy the liability line. I store my boat on the hard and if I have to fill up, I drive 12 miles to Idaho and as of 6-1, I pay $4.90. I always ask myself, why is it that the government makes more money on fuel, than the retailer? Just saying.
 
rheimb1 said:
Everybody's talking about fuel prices. The Marinas don't charge road taxes nor carbon taxes, yeah they are high, and don't buy the liability line. I store my boat on the hard and if I have to fill up, I drive 12 miles to Idaho and as of 6-1, I pay $4.90. I always ask myself, why is it that the government makes more money on fuel, than the retailer? Just saying.
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$4.90 a gallon?!?!?! Wow, that's impressive. In WA state we have the highest fuel taxes in the country if I'm not mistaken, and we home port in the San Juans, so fuel is barged in on top of everyting. Having said that, I just filled up on Monday at $7.59 a gallon. I'll trade! 🙂
 
$6.99/gallon at Swantown last Saturday.
 
Fuel has dropped 10 cents last week and 10 more the week before.
 
My cruising speed set at 2.5 gallons per hour. That equates to about 6-7 knots depending on wind and tides (currents). I only rev up to clear the exhaust elbow on occasion.
 
Slowing down helped save money.

11 Day Bellingham-Victoria- Nanaimo-Bellingham cruise stats
Total Fuel Used - 122 Gallons
Total Fuel Cost - $840 USD
Avg Fuel Cost - $6.90/gallon diesel
Cruise Distance - 302 statute miles
Fuel Efficiency - 2.5 MPG
Engine Hours - 22
Average Speed - 13.7 MPH or 11.9 knots
Distance per Day - 27.5 statute miles
Total Different Mooring Locations - 10
Mooring Cost (2 anchor, 3 marine park docks and 6 nights marinas - $435 or $39.55/night
 
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scross said:
Just doing some ballpark numbers and pondering.
We typically cruise 900 miles a season and put 75 hours on our C28 diesel engine. That’s an average cruising speed of 12 miles per hour. At 1.2 miles per gallon at that speed (with current diesel prices) we will burn 750 gallons (10 gph) or $5625 in fuel (@$7.5/gallon) for the season. Note that the majority of our cruising time is in BC where fuel is a tad more expensive. We also cruise heavily loaded so our gph burn is a tad higher too.
But, if we slow down to an average cruising speed of 8 mph, we get about 2 mpg. Yes, season total engine hours go from 75 to 112 hrs but total fuel used drops to 450 gallons (4.0 gph) and fuel costs drop to $3375. That’s actually pretty close to our actual fuel cost for the 2025 season.
That’s a fuel savings of $2250 for the season. Hmmm. I think we will be spending more time cruising at 8 mph this year!
Your thoughts?
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I’m really surprised with your fuel economy. At 8 mph my 2013 will get around 5-6 mpg. We run pretty heavy as well at times and I still manage to get 2 mpg at 21 mph, even better with a lighter load.

But yeah might as well slow down and experience trawler life for a bit.
 
Just to rub salt in the wound of high fuel prices, my 3YM30 Yanmar burns 1/2 to 3/4 of a gallon per hr at cruising speed of 6 to 7 knots depending on current and wind directions. Trolling for fish I will burn about a pint an hour. With a 18 gallon fuel tank I’m limited to a little over 200 miles before refueling at $6.90 that will burn a hole in my wallet of about $125.00 usd.
But I say spend it while you can, the kids will just put it in a yard sale and get pennies on the dollar for your hard work that you left behind for them! Bob
 
Todd Tugnut said:
My philosophy is that when I am on the boat I’m already there. So six knots or so is fine with me. I ask every diesel mechanic I meet if I’m harming my engine. The answers are mixed. Some just plain no, slow is ok. Some say slow is ok, but go flank speed five minutes near the end of the trip. I run it up occasionally. I’d be interested in what others think.
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Same philosophy here.

Mechanics(or technicians in general) are very slow to change. In my experience starting a career is kind of like going to kindergarten. We learn lessons that we apply for the rest of our lives/careers. Mechanics tend to learn from the previous generation and continue on with the same practices. So change comes very slowly driven mostly by the few who go to some sort of technical school or attend factory training. So contrary to popular belief they aren't all oracles of wisdom. I spent my whole career as a machinery reliability engineer struggling with this. I had to put together and deliver a lot of training material over the years and more often than not it's an uphill battle.

Modern common rail, electronically controlled engines burning ULS diesel and meeting environmental requirements do not foul(i.e. build up carbon) to anywhere near the extent of older technology engines. It is a good idea with turbocharged engines to run at high enough rpm so that the turbo is making a little pressure and to "blow it out" every so often or at least at the end of a run. Operating at true idle speed for long periods of time is not great but again can be mitigated by following it up with higher rpm/load operation.
 
My speeds were not slow the entire cruise. I mixed running at 8 knots (3 mpg) and 16-17 knots (2800 rpm and 1.9 mpg) to keep the turbo happy. Guessing about 60% slow and 40% fast. Normal for me is about 90% at 16-18 knots. When extended cruising we are VERY heavy.
 
theres a big fuel difference between 1100 and 1400 rpm

at 1400 you are starting to push the boat beyond hull speed and fuel use goes from 1 to 4 gal/hr

im generally 1200 or 3000 anything in the middle is wasted fuel
 
scross said:
My speeds were not slow the entire cruise. I mixed running at 8 knots (3 mpg) and 16-17 knots (2800 rpm and 1.9 mpg) to keep the turbo happy. Guessing about 60% slow and 40% fast. Normal for me is about 90% at 16-18 knots. When extended cruising we are VERY heavy.
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Ok that makes more sense. Have you re pitched your prob? I dropped down to a 21 pitch on my spare and it made a huge difference running with a load.
 
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