Speed and Wide Open Throttle Test

S

sparky

Well-known member
Joined
Jan 8, 2009
Messages
215
Fluid Motion Model
C-32 C
Hull Identification Number
FMLC2413G617
Non-Fluid Motion Model
36' Endeavour Trawler Catamaran
Vessel Name
MoonBeam
Hello all R-25rs

We finally did our first Wide Open Throttle test yesterday. The boat has 60 hours on the Cummins 130 hp. Bottom was cleaned three days earlier. 4/5 on fuel, 1/3 water. Rollup dinghy in the cave with it's parts less than 75 lbs, good supply of tools and spare parts adding some more weight, and two slim adults on board. Waves less than 1 foot in the lower Chesapeake Bay, and wind less than 10 knots.

Results: at 99% load, we were only able to hit 3560 RPM, burning 7 gph and moving barely 15 knots. :cry:

This is well below the stats on the Ranger Tug website. Max RPM should be 4000 RPM and should hit 20 knots. I realize that boat was stripped bare, but how are other owner results? The only thing that could easily be changed is the prop pitch, but we are going with the factory issue Acme.

Sparky
Starry Night
 
Something does not sound right if you are burning 7GPH and only turning up 3560 RPM. The more weight you add to a boat the lower your RPMs (and horsepower produced) will be with the throttle fire-walled because the boat can't reach its optimum speed due to the load. This is especially true with a semi displacement hull that is moderately under powered.
Henry
 
How much of a change in performance could you achieve with the trim tabs?

Seems like the speed (15Kts) matches the rpm (3500) per the Ranger sea trial data, but the fuel burn is high at that rpm so something is making it hard to push the boat through the water. Some possibilities could be weight (generator, etc) or trim?

Be interested what others have to say. I know our boat (Yanmar 110) really does well when I take all the weight off it, but outfitted for cruising, it slows down a bunch....

Mac
 
Were you going with the wind or into the wind? That could make a big difference here.
 
Those are both big factors in making it tough for the engine to reach its 4000 rpm. The other things you have to take in effect are these. Water temperature, humidity, Thru hulls are free of any debri or barnacles and how clean the bottom is.

We prop the boats here to achieve what Cummins was satisfied with. They always vary when you get to different parts of the world and certainly how each boat is outfitted.
 
I thought I'd post results of speed vs. rpm from my R-21 EC.

Yanmar says the max power rpm is 3600 and that the vessel should be propped to attain that rpm, plus 200 rpm more, 3800. The additional 200 rpm is to allow for carrying more weight than what was aboard when the prop was optimized.

My tug will do 9.5 knts. at 3375 rpm, which is the max rpm the engine will pull under load. That's with flat water and no wind, one 200 lb. person, all safety gear, a full fuel tank, no water in the holding tank or the water tank and a clean bottom without bottom paint.

Later, I saw 10.5 plus knts. surfing down a wave.

At 2800 rpm under the same conditions the tug goes 7.5 knts.

I suspect the tug is overpropped, or maybe the tach is wrong.

Gene
 
The Laurie Ann has a 110 Yanmar. Running bare boat with two people on flat water, no current or wind; at 3200 RPM we do 12-13 knots provided we trim the bow down with the trim tabs. Fully loaded for extended cruising (dingy, outboard, bikes, scuba, and full tanks and food) we drop to about 10 knots.

We prefer the 7-8 knot speed at 1800 to 2200 RPM's and achieve 5 miles to the gallon or 1.2 gallons per hour.
 
LENABELL is the only boat with the 75 hp which I believe is same engine block as 110 (smaller turbo). It sounds like my low speed performance is the same. WOT for me is only about 10 kts (several people, bottom paint, full of fuel, water and lots of junk). I think Mark said it would do 12 kts before I took delivery (1 person, no water, 10 gals fuel, no bottom paint, no junk). I spend 80% of my time at 6-7 kts and take it up to WOT for about 5 min/hr. The good part is that I used 60 gallons of fuel last year for 80 hrs operation (.75 gal/hr).
 
Commander Bill,
You are right on with the use of the tug. Maybe being here in Al. we are a little slow and don't mind relaxing and enjoying the trip. You know I have my R21 for sale so I could get a little more speed Have now bought more fuel for my C-Dory in the 3 months than I bought for the tug in 3 years. My boating need is still slow 75% of the time but I find that I push a little more just because I can. If you are ever down the Tenn. at the mouth of the Elk, stop for a visit. Charlie Stancil now lives here also.
Good boating to you! Ron
 
Thanks, Ron
By the way. I had been sitting on the fence for some time trying to decide on buying the boat. You took me out for that short trip in the river back in 2007 and now it is your fault I am in debt. By the way if anyone is thinking about a R21 Ron's boat has a unique and outstanding hard cover over the rear section of boat that everone owning a R21 tug should consider. It adds considerable value in my opinion.

Try to keep an eye on Charlie for me.
 
One thing to add to the R21. We have tried about 50 different props on this boat before Yanmar and us were satisfied. There was one key point that you missed with the 3YM-30hp. It is rated 3200-3600 RPM. We run every 21 tug at 3450-3500 RPM's. Whenever you get to different parts of the world, those numbers will always change due to all of the reasons listed above. The prop is a 13x15.5 4 blade with .090 cup. You can tweak to achieve rpm but you will always suffer in another area. (speed, fuel economy, ect...) If it is down to 3550 rpms like it is in Sparky's case then you will have to make adjustments to the prop to achieve closer to the 3900-4000 Rpm spec. with the Cummins.

Whenever you do a new engine install from any manufacturer they are required to do a technical assesment on the engine and how it performs in the boat before we start sending them out. This was done with Yanmar and Cummins on all of the engines we install.
 
Andrew,

Thanks for your comments; they make sense. But, it appears Yanmar has two positions on this rpm question, the one they've expressed with you folks at Ranger and what they tell us owners. :?

Their 3YM30 manual is quite explicit about propping at 3700 to 3800 rpm and being able to always get 3600 rpm. They reinforce that advice with the warranty stick, not a warranty carrot . See page 9, end of the left column.

I'm a long time Yanmar engine user and an avid fan of their engines. But, I also know how they sometimes respond to warranty claims.

I still need to check the max rpm the engine will run without any load, I know it will turn at least 3600 rpm without load; I saw that on the tach. How accurate do you think the tachs are on these boats?

My engine under load (load listed above), maxes out at 3375 rpm, nearly 100 rpm less than the lower rpm you mention. Are you checking/testing in salt water? Wouldn't salt water result in lower rpm than what one would get in fresh water under the same load conditions?

I know the Moore 25 and the Olsen 25, CA designed and built sailboats, will sit lower in fresh water (increased draft) than in salt water, increasing wetted surface and resulting in slower speed. I wonder if a similar effect is present for props, ie. working against a heavier mass resulting in lower rpm in salt water compared to fresh water? I also wonder if the R-21 EC has a deeper draft (sits lower) in fresh water increasing wetted surface and drag, causing reduced max rpm?

I also find it interesting that Yanmar's manual keeps advising the owner to keep an eye on temp, even giving specific temp, and didn't provide a temp gage on the panel. In fact, the last time I checked a gage wasn't even available as an option. :roll:

Gene
 
Gene,
It is correct that Yanmar does require that their engines be propped at 150 to 200 RPM's over the rated RPM, under load. If the boat's engine does not achieve this then we always check her out with a photo tach, to ascertain if the boat's tach is reading correctly. If the engine reaches the proper max RPM loaded then the boat should reach at or near the boats rated speed. If not then we need to look at boat trim or drag of some sort, of the hull's condition or perhaps the drive train. The max no-load RPM of the Yanmar 3600 RPM engines is 4000 - 4400.
Cheers,
Peter
 
Some people will say I'm being petty. But, I really expected this Ranger to be on spec., ie. the engine should perform according to specifications, the fuel tank should be properly supported and of a design such that fuel/spray does not blow back thru the fuel filler and the fuel vent. Also the fuel lines should be properly routed and tightened.

An owner of a new boat should not be expected to take care of said items.

Over the years I've installed numerous oil pressure gages, water temp gages, tachs, volt meters, amp meters, etc. Usually the factory provided lights in the circuits that gave indication of changes by varying the intensity of the light. If I didn't like that, then, then I could install gages. My point is Yanmar makes an issue of the owner closely monitoring the temp, even specifying the temp in degrees and then doesn't provide a way for it to be done. That doesn't make sense to me.

When I purchased a 20 year old Albin 27 Aft Cabin a few years ago it was in better shape overall than this brand new Ranger. I knew there was limited support for that old Albin; I expected more from Ranger. :x

Gene
 
The propeller that came with our R25 & 130hp Cummins engine has not the correct pitch to get the 4060rpm at WOT. The propeller should be changed, but you probably will not see much more than the 15k which you already observed.

Toodles
 
Best I've done is 16.9 knots at 4000-4010 rpm in an R25 with Yanmar 4BY2 150hp. Full diesel and water tanks, bottom paint, full gear, two people, generator and every option known to man... That was on flat fresh lake water.
 
I've got a question. On a previous boat we had with a Cummins engine and ZF transmission there was the ability to adjust the engine/transmission electronics and when it is done the high end rpm's are reduced. I can not recall why this is done but my question is this....do the Ranger Tugs have this ability? If so maybe there needs to be an adjustment to the engine/transmission electronics to maximize your boat engines RPM's and therefore top end speed. I'd be curious to know if anyone with more advanced knowledge knows about this or has any experience.
 
I have a R25sc 2010 with Yanmar 150hp with four people and gear. 4000 RPM's 17.5 knots 7.3 GPH
I know the engines are not the same, but the speed for the RPM's on your boats seems about right.
You might check your prop, you may have bent it. this could keep your RPM's on the low side.
Good luck
 
I have tried different props and cup settings, four to be exact and I can tell that the Cummins 130 engine with full fuel and water plus 500 lbs of load at sea level will do a maximum of 15 knots. These figures have been obtained with temperatures from 40F to 90F, with every kind of trim setting. I am a professional pilot, so I am quite "anal' in really doing a trend and these rpm's have been tried to 4060 rpm which should be max for the Cummins according to their specifications. Since this boat is normally cruising at 6 to 8 knots, I have come to accept that the 20 knots in the sales test figures will only be attained with a five knot current. BUT, I do think that this boat is great, even if I do point out its shortcommings.
 
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