Fuel Consumption Volvo 29hp

[McConnell]

Can anyone advise on what is normal fuel consumption for a 29hp Volvo engine running at 2000rpm's? It is a 40' Manta catamaran. My husband left La Paz 20 hours ago and his gages are telling him that he has already used about 50 gallons. This does not make sense! Does anyone know anything for him to look at? Could it be that the gage is not reading accurately? Please advise if you have any clues!

[Thumbs Up]

They should burn half a gallon per hour. So with two motors running they would burn a gallon per hour. Are the gauges reading in liters perhaps?

[Cotemar]

McConnell,

Maybe this chart will help.
.5 gal at 2000 rpm

[McConnell]

Thank you so much! I will pass this on to my husband next time we can connect.

[Sid at SailAway]

First to McConnell, never, ever trust a fuel gauge on a boat. They are notoriously inaccurate. The best way, IMHO,to measure the usage is by hours run.

Cotemar, I'm not sure where that chart came from, but from my experience on my boat, the usage on the chart at cruise rpm's is nowhere close to what I'm seeing in real life. At 2800 rpm I am seeing a solid .625 gallons an hour. When I plan our stops for fuel I use .75 gallons an hour as a safety number. This number comes from tracking the hours and gallons used and then doing the math. I'm not sure what I burn at 2000 rpm, but in any case, again IMHO, 2000 rpm is too slow for cruising speed. That engine needs to spin between 2700-2900 at cruising. I pulled this from the manual.

Cotemar, what did you have in your Mahe? And McConnell, tell him to speed up...

[savoir]

Are you sure about the 2800rpm? I don't know all the Volvos but 2800 seems to be more like the recommended max than the cruising revs on a Volvo. The range generally does not rev as high as a Yanmar which can be as high as 4000 rpm.

I would expect the cruising revs on a small Volvo to be more like 2200 rpm.

[Yong SC]

Hi, my FP Lucia40 cat has 2x30hp Volvos. I clocked about 3L per hour each engine at average cruising rev of 2800. Conditions of other components (oil, fuel filters etc) do impact performance.

[Moontide]

My feeling is that the only way to have any real usability/accuracy on a fuel gauge is to run tank empty then make your own table of gauge reading and amount of fuel put in. Even then it is only a guideline as many gauges do "steps" where they jump an 1/8th at a time or so rather than a smooth curve. Tracking hours and gallons when refueling are certainly the best / most reliable.

Also agree with those that say run the engines harder. Is he running both engines all the time or only one? Many (most now?) cats only run one when underway unless trying to beat a sunset or storm.

Bill

[Sinbad51]

I have a volvo model 2003 28 horsepower in a 17,000 pound mono hull.
When running 2250 rpm I use .8 gallons an hour. Based on my consumption,with twin engines and the lower rpm he should have only used around 30 gallons.

[McConnell]

Thank you all for so much for great info! It has been passed on. He did stop into Cabo to top up fuel to see how much was really used, and it did not correspond to gauge usage. He feels much better about making it to Turtle Bay! And yes, he will up the RPM's now that he knows the fuel usage does appear to be more in line with his planning calculations.

This is a new boat for us, so not sure on all of her operating specs, but we needed to get it up to the US ASAP and did not have the luxury of shakedown trips to get all of the kinks worked out!

[TrentePieds]

My 27HP Vetus (Mitsubishi K3D) burns 2L (= 1/2 US Gallon) per hour at 2K RPM. That would translate to other makes of engine pretty directly since specific fuel consumption for diesels doesn't differ much twixt makes.

20 hours * 2 engines * 1/2Gall/hr = 20 Gallons.

I agree with Sid - don't trust the gauges. Best to have a dipstick, but few boats are fitted so one can be used. Prolly due to consumers' preference for "hy tech" over utility :-)

20 gallons = 80 litres, close enuff, so if the gauges were marked in litres they would still be wrong.

But McConnell - tell you husband to have a really good look around for leaks. It doesn't take long to loose 30 gallons. As the boat is a catamaran and he's (apparently) singlehanding, he may be outta the smell of a leak, and unable to see the evidence of one from the steering position. 30 gallons is about a hundred and eighty pounds in weight so if it's sloshing around somewhere it wouldn't upset the trim of the boat noticeably.

TrentePieds

[Cotemar]

Originally Posted by Sid at SailAway

Cotemar, I'm not sure where that chart came from,

Cotemar, what did you have in your Mahe? And McConnell, tell him to speed up...

Sid at SailAway,

The Fuel Consumption chart pictured came from a Volvo Penta D1-30 spec sheet.

My FP Mahe 36 had Volvo Penta D1-30 engines and that .5 gal at 2000 rpm was accurate from my experience with those engines.

It’s very common for Captains making very long passages or deliveries to use lower RPM to keep the boat moving during low wind days.

When you’re making a 3000 mile trip across the Atlantic from the Canary’s to St. Martin you had better know how to conserve fuel.

I believe the OP (Original Post) Mr. McConnell is bringing home his new boat or doing a delivery of some kind.

So what’s good for cruisers here, is not necessarily good for Mr. McConnell trip

[Sid at SailAway]

Originally Posted by savoir

Are you sure about the 2800rpm? I don't know all the Volvos but 2800 seems to be more like the recommended max than the cruising revs on a Volvo. The range generally does not rev as high as a Yanmar which can be as high as 4000 rpm.

I would expect the cruising revs on a small Volvo to be more like 2200 rpm.

Here's where I pulled the numbers. I cruise at 2800 using one engine and make 6 knots. I've made so many fuel checks that I'm pretty confident in the .625gph burn at 2800rpm. I'm still confused as to how Cotemars chart can be so far off. Cotemar, thoughts? That's basically double what I burn.

[a64pilot]

The BSFC or Brake Specific Fuel Consumption of all small Diesels will be surprisingly close, they are all close to being equally efficient, meaning a Volvo, Kubota or Yanmar making say 20 HP will all burn very close to the same amount of fuel. Turbos and one or two other things may change it some, but not as much as you may think.

RPM to make that 20 HP may vary of course, so comparing RPM to RPM will yield different answers

[Cotemar]

Sid at SailAway,

At 2800 RPM your pretty much running at MAX RPM for a Volvo Penta D1-30 (30hp)

I have no idea what motor you have and what your specs. are.

The spec's I am posting are the ones the OP is asking about. for a Volvo Penta D1-30 (30hp).