LAGOON 450 FUEL BURN

[PaulinOz]

Not only revs but load and bottom paint condition effects fuel burn as well. Have traveled this season since May with another L450. They are less loaded and there bottom paint was new at start of trip, where as mine was 11 months old at the start of the trip.

I was onstantly 0.5 to 1 knot slower for any given engine revs or wind condition bellow 15 knots. My average fuel usage was 3.8 lt/hour his just under 3lt/hr. Over exactly the same trip so it is not just the revs that effect your range. I use 4lt/hr as a planning figure.

Bottom Paint booked for 1st week of January and the boat is going on a diet over the Xmas period.

[sailjumanji]

We played with this on my Seawind, coming across the Gulf, and having to motor on windless days. Dual 9.9 hp Yamaha high thrust outboards. Both motors running at maybe 4000 RPM's pushes the boat at 5.5 knots but uses a little under one gal per hour. Running one engine gets 4 knots at 0.5 gal per hour. We were trying to stretch fuel to get to Grand isle from ft Myers.

My fishing boat has a 250 hp Yamaha. It has a 60 gal tank but is pretty flat shape so gauge is not accurate. I hooked up the motor ECP to nmea 2000 network and my Garmin chartplotter does the fuel burn integration to reflect accurate remaining fuel volume in tank. Also shows burn rate. If I remember right, going 25 mph burns 8 gph, but 50 mph burns 36 gph. 23 ft cat hull flats boat. Built more for shallow water than speed.

So do the newer diesel engines have an ECP that you could tap into? If not, there are flowscan meters. Garmin also makes their own inline fuel meter. Not sure if any of these work for low rate diesel consumption.

[Emerald Sea]

If you are only looking for a good idea of fuel consumption for your 4JH5E then you can find the consumption curves here. We have found that they give a pretty good estimate of our fuel burn (folding props, clean hull). If you have the 4JH57's then this is also available at these links (just backtrack it a bit).

https://www.yanmar.com/media/global/...r-4JH5E-LR.pdf

[Cadence]

Originally Posted by chilihead

Any idea of how I can determine a general fuel burn rate for various rpm''s etc? Not trusting gauges (of course) so general idea is fine.
Thanks
Fred

If you can? Stick the tank making a stick when fueling, Notch the stick.

[afriis]

If you read the manual, you can find out how to show fuel flow in the engine instruments.
I have the same engines in our 450, 2016 model.
Eventually somebody is going to develop a connector to NMEA for Yanmar so We can get the ff in the B&G instrument.

[Bean Counter]

A generalized response: Over 3 years cruising average fuel use was very close to 1 US gallon per hour on Yanmar engines, and that includes Onan 11KVA generator for roughly same number of hours. (That is total fuel used divided by total Yanmar engine hours) We motor sail on one engine at around 2000 - 2200 revs to get above 6 knots. We motor with no wind at 6 - 6.5 knots on one engine at 2200 - 2500rpm. (We only rev to 2800 for short bursts of 1/2 an hour ) Clean bottoms, folding props. So as a rule of thumb I use 1gph (3.8L ph). On longer overnight passages we don't use the generator so it probably does better than that. Motor sailing would use a lot less fuel for the speed. Gulf stream currents also help heading up US east coast. There are a lot of factors affecting fuel burn, one of the worst is nose into 20+knot breeze + waves, we then run two engines at around 2200, but avoid it where we can. When motor sailing if the wind is on port side use the port engine this lets the wheel center more easily for the autopilot (and vice versa) so less rudder drag. Engines are 4JH5E

[Indigo1]

We have Yanmar 4JH5E, folding props with 17 pitch, 2000 rpm, 5.5 kn for 1 engine, 6.5 kn with 2 running, 2.2 l/hr per engine. Funny enough its about the same for the onan 11kw generator at 50 % loaded too. I check each time I fill the tanks and its proven very close to that over hundreds of hours. The graph from Lagoon for the same set up indicates far higher consumption.

[GordMay]

Greetings and welcome aboard the CF, chilihead.

[chilihead]

Thanks to all. Based on all the great information you folks provided, we decided it was best to stop for fuel on an Annapolis to Ft. Lauderdale delivery. Might have made it but not worth the risk.

[DavefromNZ]

Indigo1 I have thought the same thing that my actual fuel flow is lower than the graphs.

[StuM]

Originally Posted by PaulinOz

Not only revs but load and bottom paint condition effects fuel burn as well. Have traveled this season since May with another L450. They are less loaded and there bottom paint was new at start of trip, where as mine was 11 months old at the start of the trip.

I was onstantly 0.5 to 1 knot slower for any given engine revs or wind condition bellow 15 knots. My average fuel usage was 3.8 lt/hour his just under 3lt/hr. Over exactly the same trip so it is not just the revs that effect your range. I use 4lt/hr as a planning figure.

Bottom Paint booked for 1st week of January and the boat is going on a diet over the Xmas period.

Primarily because you need higher revs(HP) to achieve the same speed and consequently a higher fuel burn, not because you burn more fuel at the same revs.

[a64pilot]

Mispost

[a64pilot]

Originally Posted by StuM

Primarily because you need higher revs(HP) to achieve the same speed and consequently a higher fuel burn, not because you burn more fuel at the same revs.

There is a little bit of more fuel burned at the same RPM though, cause the boat has more wetted area due to being heavier and dirtier bottom, there is a lot more drag, this drag will drag RPM down some so your fuel burn will be higher than say the same RPM when motorsailing when the motors are unloaded.
An Autoprop may be the exception though as it will increase or decrease pitch to keep the engine load more or less constant for the same RPM. Either way it’s not much.

For Diesel engines, you need two flow meters per engine cause you have to subtract return fuel flow to get fuel burned, with just one meter it will look as though your fuel consumption is huge.

Also all the motors that you can get fuel flow from the bus, that is calculated fuel flow, not measured, but it’s pretty darn close.