Diesel use and best RPM for Yanmar 38hp on our IP350

[Mona1P]

So we're new to our 1997 Island Packet 350 and trying to understand the average hourly diesel consumption for the Yanmar 38hp engine, I am wlso wondering what's the most efficient RPM range when running under load?

 

[Trauphinos_]

I''ve got a similar setup on my boat with a Yanmar 3JH, when I run it around 2,600 RPM, I average just under 0.7 GPH....it is a nice balance of speed and fuel use. But I learned the hard way early on that pushing past 3,000 just burns more without real gain. You'll get a feel for her sweet spot soon

 

[Mona1P]

Thanks for sharing your experience, that RPM range sounds like a great starting point, I'll keep an eye on fuel use and speed to find the sweet spot for our Yanmar too

 

[SandyToed]

Just want to jump in and add, a good rule of thumb for average hourly diesel consumption when cruising under load is often between 0.5 to 1.0 gallons per hour, or approximately 2 to 4 liters per hour.
This can vary quite a bit depending on your cruising speed, sea state, hull cleanliness, and propeller.
I know a few who see about 0.8-1.0 GPH at their typical cruising RPMs.
For marine dieses like the Yanmar, I think the sweet spot is somewhere around 2500 - 2900 RPM, so @Trauphinos_ got good figures!
This range allows the engine to work efficiently without being lugged down or over-revved, helping with longevity and fuel economy.
Try to find the balance that gives you a comfortable speed with minimal vibration and noise, and then monitor your actual fuel burn to confirm.