RPM vs Speed vs GPH vs Range Chart

[capnlmk]

I know it all depends on the total weight of the boat, the sea conditions, etc., but has anyone put together a chart for a fully-fueled, R25SC that looks at RPM vs Speed vs GPH vs Range, going up stepwise through the RPM range of the Volvo 150 D3 engine?
The sort of chart you see in the magazines describing a new cruiser model.
I will generate the data myself, if no one else has already has, but i thought i would ask first.
Thanks.

 

[Dale777]

capnlmk,

I put together a chart mostly like what you are requesting, but for an R31 Sedan. Perhaps, what I have done will be helpful. See this link:

viewtopic.php?f=5&t=5868&p=41893&hilit=polynomial#p41893

 

[snydzy]

I'm also curious, ... Do all the 25sc models have the same reverse gear ratio? Last time I bought filters, there were three different gear ratios available for the Hs45a-A; 1.51:1, 2.03:1, 2.43:1. Wouldn't this affect such a chart? Or are all the 25sc the same?
David

 

[Red Raven]

I have the desired chart (Speed and nMpg vs RPM for each boat model with Volvo engine) in a PowerPoint file that someone previously attached to a post. I can't find that posting and I can't figure out how to do an attachment here. If someone can help explain how I'll attach it again. It is a Ranger Tugs document so I would think should be on their website but I couldn't find it there either.

Curt

 

[capnlmk]

Thanks for the comments so far. The Power Point chart sounds promising.

I made a preliminary run at collecting the data on the water yesterday, but the conditions were not ideal. I've got some ballpark info, anyway. One interesting finding: from about 2200 RPM up to 2800 RPM the range stays about the same, because the increased speed balances out the increased fuel consumption.

 

[baz]

I have the desired chart (Speed and nMpg vs RPM for each boat model with Volvo engine) in a PowerPoint file that someone previously attached to a post. I can't find that posting and I can't figure out how to do an attachment here. If someone can help explain how I'll attach it again. It is a Ranger Tugs document so I would think should be on their website but I couldn't find it there either.

Curt

Here you go... http://www.google.com/url?sa=t&rct=j&q= ... TX4Py62l4Q

or

https://dl.dropboxusercontent.com/u/86512138/R-21EC/Ranger Tugs Performance Sheets 1-15-2014.pptx

Using some of the data in the above charts I came up with this for the R-21EC with Volvo Penta D1-30

[EDIT]
BTW... according to my research/measurements/inspections the R-21EC's fuel tank can hold closer to 19 gallons... :roll:

 

[capnlmk]

Thanks. The Ranger published data is consistent with what I generated, considering differences in conditions, loads, etc.

Now I know how far I can go. ;-)

 

[Red Raven]

Great!

I started out paying attention to the "optimal" cruising speed more than I do now. My thinking was that if we had enough time we should be at "slow cruise" (what I defined as 1600 RPM and about 6 knots for our R27 D3 200hp). If we had a deadline we should be at "high cruise" (what I defined as 3600 RPM or about 16 knots). My thinking was that anything above 6 knots was going to use exponentially more fuel until you get on a "semi" plane at about 2500 RPM. Above that the speed was essentially free because our mpg stays at about 2.0 for any rpm above 2500 and 3600 is about the maximum continuous speed for the engine. While there is definitely some truth to that, I realize now is that there other factors, most notably, comfort and ride, which often result in choosing to run at a speed in between the extremes. In some conditions, the boat just rides better at certain speeds. In any case it is always quieter the slower you go and never takes "more" fuel even if the savings isn't significant.

Now we just choose the speed that get us where we need to go at the time we want to to get there with the most comfort. The cool thing is the boat handles and rides really well, and is economical, at any speed you choose! That is one thing in my opinion that makes these great boats.

Curt

 

[capnlmk]

Speaking from the viewpoint of a sailor for almost 50 years before becoming a "tugboater," I figure anything above 6 knots is gravy!

We are loving our little Ranger tug. Much different from the 46-foot ketch we sailed for the past 8 years. It was time to downsize and simplify.

😀