ideal cruise speed/rpm on yanmar4BY2150

[co2tugman]

Anybody have any thoughts on the sweet spot on the R25SC regarding speed,RPM and noise levels?
We are taking delivery next weekin Seattle. Most of our cruising will be in Puget Sound,The San Juan and Canadian Gulf Islands.
Thanks

 

[GulfSailor]

Here are the figures for the C26 with a 4BY2-180, which is pretty close.
It should at least give you something to ballpark.

 

[BaseCampAnne]

I have wondered about that also; when I asked Kenny he reminded me that our boats can vary a great deal in weight depending on what all we have added on, how many people (and pets) are aboard, how we are loaded, such as for a day trip or a two week cruise to Desolation Sound. Tugnuts also consider tides and currents. And of course the winds can be a factor...

I have not found a clear and specific answer to my question, but the chart is a starting point. Going slow clearly burns much less fuel.

I am also finding that sometimes I choose to burn more diesel to get to a destination or back due to various issues such as weather, etc.

I prefer to travel with the door closed to cut the noise, and have not developed an ear for a good sound for the engine. As a sea kayaker, I tend to avoid any focus on the engine sound, although that probably is a useful habit.

Whatever the fuel usage, this 25SC is fun and comfortable at various speeds and in different kinds of weather!

 

[RProffer]

I don't know about the Yanmar manual for the 4BY2150. The manual for the 3YM30 has all the RPM's for everything, break-in RPM, fast cruise RPM, slow cruise RMP, max RPM, etc. Speeds for a specific RPM will vary depending upon wind, current, load, etc. I recommend reading the manual for a start. You can download the manuals here http://www.yanmarmarine.com/index.cfm/go/Powerboat-engines//

 

[Barry Cohen]

YOLO (2011 R-27) has the 4BY2-180. Yesterday, we were cruising the outer Boston Harbor off Boston Light. The water was like glass and there was bearly any wind.

I had 3 good size gents and 3 gals aboard. Full tank of clean water, half tank of fuel and probably half tank of black water. At WOT, I could only get up to 3950 RPM and 14.5 knots. As far as noise, nothing of note. For my money, the engine purrs!

Not sure if this is due to all the weight or if I need a throttle adjustment.

So far, having a fantastic summer in Massachusetts Bay. Hope everyone had a great 4th. Our one-of-a-kind maritime military history was well represented in Boston Harbor.

 

[abcandjrc]

.......I had 3 good size gents and 3 gals aboard. Full tank of clean water, half tank of fuel and probably half tank of black water. At WOT, I could only get up to 3950 RPM and 14.5 knots.......

For the load you were carrying, you were probably "over-proped", i.e. too much pitch. The factory uses a pitch for a "typical" load, which might not be "typical" for any given user. That is fine if you don't carry that kind of a load all the time, but if that is a "typical" load, you might consider having some of the pitch removed. You won't necessarily go any faster but you won't be overloading the engine.

Try taking the boat out with a light load, maybe just you, and see if the engine will reach max. RPMs. If it does, and the load you had over the weekend was not your normal load, you are probably good-to-go as is.

 

[rt11002003]

Remember, we're talking "max rated rpm" which should be stated on the engine data plate and used to select a prop considering what one would normally carry on the boat. Also, it is usually recommended that one prop at "max rated rpm" plus a couple hundred more rpm to allow for accumulating gear. If one should overload the boat temporarily it is advisable to avoid prolonged operation at higher rpm.

gene

 

[wefings]

Max RPM is @4k , that's great prop [and engine] performance for 6 people with fluids and gear. 50 RPMs below red line is great and is showcasing the diesel's torque and load carrying abilities . Bottom paint will drop the RPMs as well as load . All modern engines have rev limiters [which protect from over turning ] Not a problem with Rangers as they prop them with the Yanmar distributor's assistance for best all around performance.
Marc

 

[abcandjrc]

Max RPM is @4k , that's great prop [and engine] performance for 6 people with fluids and gear. 50 RPMs below red line is great and is showcasing the diesel's torque and load carrying abilities . Bottom paint will drop the RPMs as well as load . All modern engines have rev limiters [which protect from over turning ] Not a problem with Rangers as they prop them with the Yanmar distributor's assistance for best all around performance.
Marc

Marc, (and Barry)

My bad.... My reply was accurate except for the 'you's in "For the load you were carrying, you were probably "over-proped", i.e. too much pitch."

I had done the big error in assuming his 3950 RPM was well below max operating RPM. I should have looked up the spec myself.

I did today after reading your reply, and darned if Yanmar hasn't "simplified" the manual to the point where torque and hp curves are no longer included, nor recommended operating times at various engine load. (At least after several documents and about 10 minutes to find a figure, all I could find was max RPM.) No wonder so many questions are asked here.

Of course, hardly anyone ever reads his manuals. (Just me and RProffer? :lol: ) Not that it would have helped that much with this engine. When I worked for GM, when the 'G' meant "General" instead of "Government", we used to joke that the least-used part of the car was the book in the glove compartment.

 

[RProffer]

On the Technical Datasheet for the 4BY2150 http://www.yanmarmarine.com/theme/y...chnical-datasheets/PDF/4BY2-150 4BY2-180.pdf, it says Max RPM is 4000 RPM and Continuous Rating Output is 3600 RPM. I would assume the Continuous Rating Output would be Max Cruise RPM. This document also has the performance curves. Looking at the curves, my guess is you would get the best performance and mileage between 2200 RPM and 3300 RPM. (I am not an expert looking at the curves.)

According to page 9 of the Operation Manual http://www.yanmarmarine.com/theme/y...-engines/Operation-manuals/BY2_OM_23OCT09.pdf,
"This engine is designed for pleasure boat
applications. The engine is designed to be
operated at: maximum throttle for less than
5% of its total operation time (30 minutes out
of every 10 hours). The engine should be
operated at cruising speed (3200 - 3300
rpm) for less than 90% of its total operation
time (9 hours out of every 10 hours)."

I would recommend going to 3600-4000 RPM for about 5 minutes every hour to clean out the carbon, then go back to cruise RPM. I hope the above information helps.

Back in 1983, when I was in the Navy, I got transferred to a new command who had just received new computers. Computers were new at that time. The other guys in my division were too busy on a project that was due, to teach me anything, so I was on my own. I did the tutorials for the computer and read the manuals. Next thing I know, I was being called the computer expert - just because I read the books. In 2010, when I ordered my boat, I read all the relevant posts on Tugnuts and C-Brats, then found and read the manuals for the Yanmar engine and Garmin equipment. I knew that with diesel engines if you gave it clean fuel and treated it properly, it would last forever. Well, I am hoping this will be the last boat I will buy (unless I hit the lotto), so I want to take care of the engine so it will last. I just retired, so I want this boat to last.

 

[Zundels]

With our 2009 R-25 Cummins 150 it was suggested by a diesel mechanic, with the variability of loads as mentioned above, to run at a top speed of 75% of engine load. This is a quick and initial gauge to judge the speed.

 

[SEEKER]

Anybody have any thoughts on the sweet spot on the R25SC regarding speed,RPM and noise levels?
We are taking delivery next weekin Seattle. Most of our cruising will be in Puget Sound,The San Juan and Canadian Gulf Islands.
Thanks

We typically cruise our 25SC at 3600-3700 RPM's which puts us at 6.2-6.7 gal/hr at 12kts-14knts depending on load, tide and wind. At these RPM's we are usually between 85-90% load on the engine according to our gauges. We'll run like that for 2-3 hours sometimes. Noise level does not seem to really change until you get to 2500 RPM's or less than it becomes an nice economical cruise with much lower noise levels and incredible range at or around 7 knts, this seems to be the laid-back way to go without having to worry about spilling you GnT. Have have to say the noise is the last thing I really think about, these boats are pretty quite, you can have a normal conversation when cruising at nearly WOT as long as the door is closed.