New member saying hello and a question on fuel consumption

[MattZ]

Hello all, thanks for letting me join. I've been sailing for 50 years but have moved to a new area where a trawler would be an ideal boat so it's time to make the switch. I've been looking at used boat ads and while there are a lot of beauties out there, they mostly aren't in the budget. One that might be is an Integrity 34 ES. I've read that they're good boats other than possible osmotic blisters. I fixed a few hundred of them once on a Catalina 30, and I have no intention of ever doing that again. At any rate this boat has twin 180 Yanmars. I'd prefer a single engine but can't wait forever for one to come around. I saw a post here saying a boat of the same type used 35 L (9.25 gal) per hour in the open ocean. I'll be on sounds and bays in NC and based on my apples to oranges comparison 9.25 gal/hour sounds like a lot. To the folks out here that have experience with this make/model of boat, does that sound like a reasonable consumption rate?

 

[Comodave]

Welcome aboard. As a guess I would think that at trawler speeds you would probably burn about 3 to 5 GPH.

 

[SteveK]

I spent about 8 grand on a set of sails, which granted can last many years. In comparison I can burn thru diesel for 4-5 years with an average 100 hours engine hours.

 

[mvweebles]

Welcome to TF. It's all about speed. Just like sails - if you want high speed/performance, you'll have to write a bigger check. Along with controls to shape the sail

I don't know the Integrity. A quick Google showed this boat. Assuming it's roughly right, 9-1/4 gph sounds like above hull speed for this boat. Maybe 10-12 knots? Run it at 7.5 knots and you'll arrive much sooner than under sail, and you'll burn 4-1/2 gph.

Peter

 

[BruceK]

Integrity are built by Jiang Hua who built IG/Halvorsen in China. The "34ES", probably really a 346ES, has a flybridge,has IG antecedents, is typical semi displacement in design. Blisters can be paint reaction above, not within the gelcoat, rather than true osmosis but can be generalized so a soda strip may be indicated rather than individual fix. I don`t think fuel consumption of the Cummins 6BTs in my 386 is much different to twin Lehmans in my old IG36, but it`s a way better boat, sea keeping included. Planing attempts would be noisy, bow raising, water churning, and semi successful, though maybe the extra hp would actually do it, despite alarming fuel consumption.
Mine has plenty of space between the engines in a commodious ER, I expect the 346ES is similar. From recollection(not experience), Yanmars need a major service at 1000 hours.

 

[tiltrider1]

Lot a factors affect fuel consumption. How long is a boat, how wide is a boat, and how heavy is a boat? No of these come close to the affect speed has on a boat.

I weigh in at 60,000# and I travel at 10kts. I burn 10gph. If I dropped to 5kts I probably would burn 3gph. My boat is capable of 15kts but it would burn 30gph.

Its really hard to give some one expected fuel consumption, are you running full fuel and water or running empty? Are you going fast or slow? Is your bottom clean or dirty. Everything has an effect.

On average (no boat is average) one can expect between .75 to 2 nautical miles to the gallon for most recreational boats at hull speed. Big range but recreational boats range from 80’ to 25’.

 

[O C Diver]

The boat in my avatar gets:
5 MPG at 6 knots
3.5 MPG at 7 knots
2 MPG at 8 knots

This is with an efficient engine that was properly sized for the boat. The boat is 45' in length. From the above, you can clearly see that there is a sweet spot at 6 knots. Increasing the speed by only 2 knots can consume over 3 times the fuel.

If the boat is 34', I would expect fuel consumption to be under 2 GPH at 6 knots. At 7 knots, I would expect less than 4 GPH. At 8 or 9 knots the bow goes up, the stern digs a hole, and fuel consumption exceeds speed.

Without a picture, this boat may plane, which could mean at 15 knots it's burning about 10 GPH.

Ted

 

[BB-marine]

I have a 34' Mainship pilot. twin 240hp Yanmar 4LHA STP engines. The pilot 34 has a water line length of 34'. @ 8kt ( 9.3mph) this is above hull speed for the semi-displacement hull. I average 3.8 gph at this speed. The engines are turning 1450 to 1500 rpm. The engines turn 3400 rpm @ wot. If I bring the throttle back to 1200 rpm the speed is decreased to 7 kts (8 mph) and the fuel burn average is 2.8 gph. The calculating mpg there is not much difference ( 3.8 gph = 2.44 mpg @ 1450 rpm 9.3 mph 8kts. ) 2.8 gph (2.8 mpg @ 1200 rpm 7kts 8mph.) about .4mpg difference. In my opinion good fuel economy for a semi displacement boat that is 34' water line length making 8kts. If I dropped to 1000 rpm the fuel economy really kicks in but I do not have good stats because I have not run the engines at this speed often. I did operate the engines for a few days at 1000 rpm 5.5 to 6 kts while on the Erie Canal and realized exceptional fuel economy for those few days. I don't like running my engines (4LHA STP Yanmar) at 1000 rpm for long periods of time.

At 14kts (16 mph) fuel burn is between 9.5 and 10 gph and average 1.6 mpg. At 18kts (20.5mph) fuel burn is 16gph and average 1.28 mpg. 18kts = 2700 rpm which is my high cruise speed. I don't have stats for any high speeds because I don't operate for any length ofttimes above 2700 rpm and 18kts. I believe at WOT the fuel burn is about 28gph and the boat will make 27mph to 29 mph depending on conditions and how we are loaded.

I don't think the Integrity 34 will perform the same at higher cruise speeds but I believe that it will have about the same at 10 kts or less. If you are purchasing the boat to cruise like you did in a sail boat for 50 years you will have a boat that will give you decent fuel burn rates for a boat of its size. You will actually be able to cruise a bit faster than the sail boat and still get good fuel economy with the twin180 hp Yanmar. I would suspect better fuel economy than my numbers. We did the Loop in 2022-2023 my total average fuel economy for the entire loop was 2.2 mpg. This is a combination of 14 months of cruising. high cruise speed and "LOOPER SPEED". I would not worry about spending to much money on fuel with the boat you are looking at.
Brian

 

[Shrew]

First off, I'd suggest sticking with GPH rather than MPG. Running with a 2knot current/tide vs running against a 2 knot current/tide is going to be a difference of 4 KPH for the exact same time period. In GPH the variable that changes is TIME rather than speed.

 

[tiltrider1]

Also pay attention to mph claims verses nmph claims. Some speak in miles, others in nautical miles. They are different. Sales people usually speak in MPH, the number looks less scary that way. Old timers usually speak NMPH. Here I see a mix of both.

 

[MattZ]

View attachment 163040Welcome to TF. It's all about speed. Just like sails - if you want high speed/performance, you'll have to write a bigger check. Along with controls to shape the sail

I don't know the Integrity. A quick Google showed this boat. Assuming it's roughly right, 9-1/4 gph sounds like above hull speed for this boat. Maybe 10-12 knots? Run it at 7.5 knots and you'll arrive much sooner than under sail, and you'll burn 4-1/2 gph.

Peter

Thank you Peter, that's helpful and reassuring. 9 1/4 sounded pretty high but I'm no expert.

 

[MattZ]

Integrity are built by Jiang Hua who built IG/Halvorsen in China. The "34ES", probably really a 346ES, has a flybridge,has IG antecedents, is typical semi displacement in design. Blisters can be paint reaction above, not within the gelcoat, rather than true osmosis but can be generalized so a soda strip may be indicated rather than individual fix. I don`t think fuel consumption of the Cummins 6BTs in my 386 is much different to twin Lehmans in my old IG36, but it`s a way better boat, sea keeping included. Planing attempts would be noisy, bow raising, water churning, and semi successful, though maybe the extra hp would actually do it, despite alarming fuel consumption.
Mine has plenty of space between the engines in a commodious ER, I expect the 346ES is similar. From recollection(not experience), Yanmars need a major service at 1000 hours.

I saw a youtube video of a 386 and was really impressed with it, beautiful boat and very well laid out. Unfortunately there are no used ones for sale in the US so you must have a rare boat. Thanks for the tip on the 1000 hour service.

 

[MattZ]

Lot a factors affect fuel consumption. How long is a boat, how wide is a boat, and how heavy is a boat? No of these come close to the affect speed has on a boat.

I weigh in at 60,000# and I travel at 10kts. I burn 10gph. If I dropped to 5kts I probably would burn 3gph. My boat is capable of 15kts but it would burn 30gph.

Its really hard to give some one expected fuel consumption, are you running full fuel and water or running empty? Are you going fast or slow? Is your bottom clean or dirty. Everything has an effect.

On average (no boat is average) one can expect between .75 to 2 nautical miles to the gallon for most recreational boats at hull speed. Big range but recreational boats range from 80’ to 25’.

Thanks. I was just looking for a rough estimate and sanity check on the consumption I saw mentioned in a post here. I figured someone would have the same or similar boat. Based on that post being about a delivery they probably weren't concerned about consumption since it was someone else's fuel.

 

[MattZ]

I have a 34' Mainship pilot. twin 240hp Yanmar 4LHA STP engines. The pilot 34 has a water line length of 34'. @ 8kt ( 9.3mph) this is above hull speed for the semi-displacement hull. I average 3.8 gph at this speed. The engines are turning 1450 to 1500 rpm. The engines turn 3400 rpm @ wot. If I bring the throttle back to 1200 rpm the speed is decreased to 7 kts (8 mph) and the fuel burn average is 2.8 gph. The calculating mpg there is not much difference ( 3.8 gph = 2.44 mpg @ 1450 rpm 9.3 mph 8kts. ) 2.8 gph (2.8 mpg @ 1200 rpm 7kts 8mph.) about .4mpg difference. In my opinion good fuel economy for a semi displacement boat that is 34' water line length making 8kts. If I dropped to 1000 rpm the fuel economy really kicks in but I do not have good stats because I have not run the engines at this speed often. I did operate the engines for a few days at 1000 rpm 5.5 to 6 kts while on the Erie Canal and realized exceptional fuel economy for those few days. I don't like running my engines (4LHA STP Yanmar) at 1000 rpm for long periods of time.

At 14kts (16 mph) fuel burn is between 9.5 and 10 gph and average 1.6 mpg. At 18kts (20.5mph) fuel burn is 16gph and average 1.28 mpg. 18kts = 2700 rpm which is my high cruise speed. I don't have stats for any high speeds because I don't operate for any length ofttimes above 2700 rpm and 18kts. I believe at WOT the fuel burn is about 28gph and the boat will make 27mph to 29 mph depending on conditions and how we are loaded.

I don't think the Integrity 34 will perform the same at higher cruise speeds but I believe that it will have about the same at 10 kts or less. If you are purchasing the boat to cruise like you did in a sail boat for 50 years you will have a boat that will give you decent fuel burn rates for a boat of its size. You will actually be able to cruise a bit faster than the sail boat and still get good fuel economy with the twin180 hp Yanmar. I would suspect better fuel economy than my numbers. We did the Loop in 2022-2023 my total average fuel economy for the entire loop was 2.2 mpg. This is a combination of 14 months of cruising. high cruise speed and "LOOPER SPEED". I would not worry about spending to much money on fuel with the boat you are looking at.
Brian

Thanks for the detailed answer Brian. I will most likely just putt along at hull speed or less. Hopefully my days of being in a hurry are behind me but it's good to know it could go somewhat faster in a pinch.

 

[MattZ]

Also pay attention to mph claims verses nmph claims. Some speak in miles, others in nautical miles. They are different. Sales people usually speak in MPH, the number looks less scary that way. Old timers usually speak NMPH. Here I see a mix of both.

If they say "knots per hour" they'll have a hard time regaining any credibility.

 

[tiltrider1]

When it comes to deliver you need to determine what is the real expense. Is it crew cost or is it fuel. A friend of mine told the delivery skipper that the speed would be no less than 20kts. The burn rate was 125 gph. The trip was 30 hours. Fuel cost was $15,000. I asked him why so fast? His answer, crew cost was $3,000 day after taxes and a 5 day storm was on the way.

 

[BruceK]

I saw a youtube video of a 386 and was really impressed with it, beautiful boat and very well laid out. Unfortunately there are no used ones for sale in the US so you must have a rare boat. Thanks for the tip on the 1000 hour service.

They are rare, I think. When I searched, I found only a review, of the actual same boat I bought. Haul out guys, looking for information about it, had the same experience. I think it`s the same hull as the more common single deck 380 model. Mine was delivered by sea from Melbourne 600 miles back to Sydney where it was first sold as the dealer`s demo boat. One night at sea, the guys called to say "surf is up" and they were going into a nearby port, so we know they are seakindly boats. I hope you find a good boat.

 

[BB-marine]

First off, I'd suggest sticking with GPH rather than MPG. Running with a 2knot current/tide vs running against a 2 knot current/tide is going to be a difference of 4 KPH for the exact same time period. In GPH the variable that changes is TIME rather than speed.

GPH means nothing unless a movement of the boat is in the equation. The original post asked a question.
"I saw a post here saying a boat of the same type used 35 L (9.25 gal) per hour in the open ocean. I'll be on sounds and bays in NC and based on my apples to oranges comparison 9.25 gal/hour sounds like a lot. To the folks out here that have experience with this make/model of boat, does that sound like a reasonable consumption rate?"


9.5gph at what speed? 9.5gph @8kts is not good 9.5gph @ 15kts not so bad. If you only care about fuel burn it really means nothing unless you use the vessels speed over water in the equation. Speed over water does not change with current or against current. To calculate fuel burn rates you need more than GPH to mean anything.

Example if I say my boat burns 2.5 gph. What does that mean in fuel calculations? Nothing! You must put the vessels speed over water in the calculation for it to mean anything. You have no control over, river down stream currents, Gulf Stream currents, tidal currents, no mater what boat you have. You either get an positive or a negative push.

Vessel speed (over water) must be included and it does not matter if you use mpg or nmpg as long as you are comparing apples to apples. If 2.5gph @ 8kts= 3.2nmpg or 3.68 mpg. Same fuel economy . 2.5gph @ ? = ?. Without speed it means nothing!
Brian

 

[SteveK]

I use GPH because I do not want to calculate how many miles I have traveled and how many gallons are used. I fill the tanks full, note the hour meter, use fuel and when I fill up again divide the gallons by the hours clocked. Not exact science unless you have a flow meter.

How many MPG or NMPG is running up a river at 5 knots into a 5 knot current? zero, but a lot of GPH

 

[BB-marine]

I use GPH because I do not want to calculate how many miles I have traveled and how many gallons are used. I fill the tanks full, note the hour meter, use fuel and when I fill up again divide the gallons by the hours clocked. Not exact science unless you have a flow meter.

How many MPG or NMPG is running up a river at 5 knots into a 5 knot current? zero, but a lot of GPH

I get what you are saying. You are calculating your fuel burn of your engines. That tells you one thing. How many gallons you burn per hour. This is good information for engine maintenance. Better to use fuel use over hours of engine operation for fuel filter changes or oil changes. Many engine manufactures use fuel burn to predict engine life expectancy rather than engine hours.

When a boat owner is questioning fuel economy, engine performance and fuel burn rate of a vessel. (GPH ) is only one number of the equation. Knowing fuel burn (GPH) tells the vessel owner how many gallons of fuel used. How do you find the best economical speed to operate your engines with only one number "gallons per hour"?

There are two numbers needed. Rate of fuel burn and vessel speed over water. The two numbers will give you a good estimate of your best fuel economy and how much fuel is needed to push the vessel though the water at a specific speed. A vessels speed over water is does not change if it is going against a 5kt current or with a 5kt current. Speed over ground does and can not be used to calculate fuel used per mile unless the current is included in the calculation. If a vessel is operating against a 5kts current and making 3 kts of headway over land it is going 8kts over water. If the vessel is operating with a 5 kts current and making 13kts overland of headway the vessel is making 8 kts over water. The engines fuel burn rate is the same as the vessel moves through the water at the same speed.

Knowing the vessels speed over water/ engine RPM / GPH will help determine the best rpm to operate the engine or engines.

Think about it. If we only use GPH to state how efficient our vessels operate what is that really stating. Example: (Boat owner A) says "I burn 4GPH at 1500rpm" ( Boat owner B) says " I burn 1.5 GPH at 1500rpm. Which boat is more efficient traveling through the water?

You don't know unless you enter the vessels speed over water.
Brian

 

[SteveK]

Brian, I agree with what you say expect 5+8=13
The problem for me is I do not have a way to measure fuel consumption with various speeds over water or land. So I measure engine hours, yes that gives an indication for oil changes and other service but is easily skewed and depends on how long idling, at 1000 at 1500 at 2000 you get picture. Unless you have an accurate way to determine the actual use it is guesswork.
But I do know when an engine is purring and when it is labouring.

 

[BB-marine]

you say expect 5+8=13

Thank you for reading my post and bringing my math mistake to my attention. I edited my mistake.


Brian

 

[Pier Pressure]

Hello all, thanks for letting me join. I've been sailing for 50 years but have moved to a new area where a trawler would be an ideal boat so it's time to make the switch. I've been looking at used boat ads and while there are a lot of beauties out there, they mostly aren't in the budget. One that might be is an Integrity 34 ES. I've read that they're good boats other than possible osmotic blisters. I fixed a few hundred of them once on a Catalina 30, and I have no intention of ever doing that again. At any rate this boat has twin 180 Yanmars. I'd prefer a single engine but can't wait forever for one to come around. I saw a post here saying a boat of the same type used 35 L (9.25 gal) per hour in the open ocean. I'll be on sounds and bays in NC and based on my apples to oranges comparison 9.25 gal/hour sounds like a lot. To the folks out here that have experience with this make/model of boat, does that sound like a reasonable consumption rate?

Matt

The Integrity is rare on the east coast of North America, I have a 2007 496CE, Bill Kolkmeyer in Milford Connecticut brought them in and some were sold out of Annapolis Sail Yard. They are good seaworthy boats, we had a few gelcoat issues above the water line, watch the deck penetrations for water ingress. Yanmars are as good on fuel as any built, fuel consumption is based on horse power demanded from the engine and can be roughly estimated at 20hp/gallon consumed. If you have the transmission reduction and prop size you can calculate it using a propeller sizing site like vicprop.com. I will caution you that if 1or2 gallons per hour is your deciding factor you may want to stay with sail as there are far more systems on a power boat that will demand your money more than the fuel tank.

 

[seabum]

Hello all, thanks for letting me join. I've been sailing for 50 years but have moved to a new area where a trawler would be an ideal boat so it's time to make the switch. I've been looking at used boat ads and while there are a lot of beauties out there, they mostly aren't in the budget. One that might be is an Integrity 34 ES. I've read that they're good boats other than possible osmotic blisters. I fixed a few hundred of them once on a Catalina 30, and I have no intention of ever doing that again. At any rate this boat has twin 180 Yanmars. I'd prefer a single engine but can't wait forever for one to come around. I saw a post here saying a boat of the same type used 35 L (9.25 gal) per hour in the open ocean. I'll be on sounds and bays in NC and based on my apples to oranges comparison 9.25 gal/hour sounds like a lot. To the folks out here that have experience with this make/model of boat, does that sound like a reasonable consumption rate?

as many on this forum did, after 37 years of sailing I went with a trawler. Our boat is a Mariner, Orient 38 with with twin Cummins 270 hp engines. At about 9.5 to 10 knots, over the last 500 or so hours I have averaged 7.2 gallons per hour total for both engines.
Summer dockage, winter storage and insurance prices don’t change with a boat’s usage. Stay at the dock and save a few grand on fuel, or use the boat as much as you can and it will still be far cheaper than the cost of this fixed expenses.

 

[Ocean Bear]

Hello all, thanks for letting me join. I've been sailing for 50 years but have moved to a new area where a trawler would be an ideal boat so it's time to make the switch. I've been looking at used boat ads and while there are a lot of beauties out there, they mostly aren't in the budget. One that might be is an Integrity 34 ES. I've read that they're good boats other than possible osmotic blisters. I fixed a few hundred of them once on a Catalina 30, and I have no intention of ever doing that again. At any rate this boat has twin 180 Yanmars. I'd prefer a single engine but can't wait forever for one to come around. I saw a post here saying a boat of the same type used 35 L (9.25 gal) per hour in the open ocean. I'll be on sounds and bays in NC and based on my apples to oranges comparison 9.25 gal/hour sounds like a lot. To the folks out here that have experience with this make/model of boat, does that sound like a reasonable consumption rate?

Hello MattZ. My boat weighs about 30 tons and with 2 Cummins 405's it burns about 16 LH- about 4.23 GPH