Survey (for the R-21EC gang)

[Kamalani]

I'm sure that when Karma posted their "Survey" asking about comparable curising speeds, they weren't expecting so many responses from the R-21 set. Well we may be small, but we still like to have an opinion on everything!

Actually, that thread just refreshed my curiosity about the speed vs RPM settings for the 3YM30 and the 21. We have found that WOT for Kamalani is usually just shy of 8.0 kts, (7.6 - 7.9) with an RPM of between 3100 & 3200. I have always thought that this was on the low side, but salesmen will tend to overinflate these things.

So, just for fun, what WOT speed & cruising speeds do our fellow mini-tuggers get, & am I in the ballpark?

 

[Gregg]

Solo, I easily hold 3400 rpm full open with 10+ (occasionally 11) knots on the Garmin GPS. I show about 3200 rpm with company on board and gear. I think about 9.5 knots was the best speed I recall loaded-up, but now I'm pumped to take the boat out and get back with some definitive numbers! 😀 Cruise is 2400 rpm at 6-6.4 knots. It's the sweet spot on my engine; a comfortable low growl and very little oscillation.
Cheers,
Gregg

 

[Stella Maris]

Actually, I was curious at what speeds all the different sizes cruise at. It seems most people are happy at around 7 to 8 knots in the non-r21 models. The R-21 seem to cruise between 6 and 7 knots due to the limitations of the motor.

As with Eric and Stuart, it is not about how fast you get there, it is about the journey along the way.

 

[dloop]

We cruise in the 7-8 knot range. WOT on our 3ym30 is 3800.

 

[rt11002003]

Interesting answers. I usually cruised at 2600 rpm, just shy of 7 knots (GPS). Puttered around at 2000 rpm, nice! WOT under load was 3300 to 3400 rpm, 9+ knots in flat water, light wind; 10+knots surfing waves down wind.

gene

 

[Kamalani]

Well I'm getting the sense that my engine's throttle stop might be set low, particularly if "dloop" can get 3800 WOT. The warnings about resetting the stop are dire, so I would never touch it myself. There are so many variables at play here, (ie: weight of boat, crew & gear, prop pitch, etc.), where do you begin? Andrew! Help!

 

[K7MXE]

I did a test with my R21EC under what I would call perfect conditions. Fresh water, no wind, pretty much empty boat with one person onboard. I do not remember the rpms but on the gps it would do 10.0 kts and nothing more.
Now for what it is worth a prop change was made in early 2006 to the first of the R21EC models. The factory provided upgraded props. My boat made middle of the year had the upgraded prop on it. Since then there might have been one very small pitch change.
I had the chance to get on it leaving the locks at Bonneville Oregon and got it up to 18kts but I can tell you it sure was a hand full and I backed up very fast. Thats all I know Bob Heselberg in Eatonville Wa

 

[rt11002003]

My memory tells me the MAX RATED RPM is 3600. That's the WOT rpm one should shoot for with the engine in gear. The max rpm one can attain when operating the vessel may be (and likely is) different.

"TUGLET" could only reach 3400 rpm, at best. Usually 3300 to 3350 was max. There are several variables in play, primarily prop pitch and boat weight. I seem to recall Jeff and Andrew telling me Ranger went thru 22 different props before deciding which to use.

Yanmar recommends a prop that allows the engine to reach MAX RATED RPM, plus 200 rpm to allow for stuff we accumulate on our boats. Since I couldn't even get the recommended 3600 rpm, much less the additional 200 rpm I had to diet the entire time I owned the boat. :lol:

The engine, out of gear, would reach 4050 rpm.

Messing with fuel stops is best left to experts. I didn't even look at mine. 😉

gene

 

[Kamalani]

Thanks, Gene - I was wondering if running up to WOT with no load, (trans in neutral), was possible... or advisable. I've never had the guts to try it. But your engine didn't fly apart at the time? :shock:

Anyway, I promise not to meddle with the throttle stop; and yes, I too could stand to lose some weight. What better reason can I have, if not to try to get an extra kt out of "Kamalani"? 😳

 

[rt11002003]

Kamalani,

The Yanmar manual recommends one run the engine in neutral at max rpm for several seconds, several times, before shutting down. I'd run mine for 5 seconds, 5 times. It is supposed to help keep the engine carbon free.

I used to do the same thing, for the same reason on my new 1971 Triumph Tiger motorcycle and my early MGA and Triumph TR3. Rode that motorcycle about a year, spent at least as much time working on it as I did riding it. Kept getting passed on the Autobahns by the ultra quiet BMW motorcycles, which I called Whisper Jets. Sold the Triumph, bought a 1972 BMW, brought it home in 1976. Been riding BMW's since then.

gene

 

[JohnH]

One more set of data points: (My boat is a 2011 model R21-EC, delivered in 2010.)

All speeds are GPS readings, using my best attempt to find slack water conditions or average out the effects of current. RPMs are as indicated on the tach. 1-2 persons aboard, fuel between half and full, water about half, standard batteries, no AC or other unusually heavy equipment.

WOT = 3750 rpm @ 8.5 kts
"Fast cruise" = 3000 rpm @ 7 kts
"Cruise" = 2400 rpm @ 6 kts

We normally travel at 6-7 kts.

I don't know if the WOT rpms are limited by the prop or by some governor on the engine. (Does anyone know if there is a governor and what its setting might be?) I wonder if I could use a prop with a slightly more aggressive pitch.

-- John H

 

[BlueDragonfly]

I'm getting exactly the same as John H with Blue Dragonfly, delivered new this last spring.

 

[rt11002003]

If I'm reading these posts correctly, there are three R21EC's turning rpm in excess of MAX RATED RPM. Also, sounds like they are newer boats. Has Ranger changed props? Actually the numbers aren't in excess of Yanmar recommendations for allowing for additional weight to be added. But, John H., your speed at those rpm is lower than my experience. I'd question the pitch of the prop.

The main issue with excess rpm is reduced loading of the engine. Diesels should operate under proper load.

Governors have nothing to do with operating rpm under load; they set absolute max rpm. Exception: one could have a prop that allowed the engine to reach absolute max rpm. In that case, messing with governor is not called for; find a prop that puts you around MAX RATED RPM.

gene

 

[dloop]

There was a thread relating to WOT on 21EC's a while back. Back then, like here with this thread, the newer ones were able to get at or near 3800 WOT, while older ones were lower. I figured there must have been a prop change along the way but I don't know that for a fact.

When I don't care as much about fuel consumption, I cruise at 3200, but even at that high rpm I probably consume less fuel than 95% of the boats out there.

(perhaps the remaining 5% are sailboats actually under sail 😉 )

dave

 

[JohnH]

I assume that the diameter and pitch are stamped on the prop, but my boat lives in the water and so I probably need to wait until it is hauled to read the numbers. My general feeling has always been in line with the suggestions about prop pitch made in this thread-- slightly bigger pitch would be desirable on my boat. I don't know the "granularity" of "standard" pitch sizes. It is possible that the next available pitch in a 4-bladed prop of our diameter would be too aggressive. Support for this concern comes from noting that respondents whose boats did not get near 3800 rpm generally only reached 3400 rpm, which is below max rated rpm. I don't know which is the better trade-off for engine health or for fuel economy, although boats with bigger pitch numbers are almost certain to go faster at any particular rpm.

Do any of the folks whose rpms peak at around 3400 know the diameter and pitch of their props? I assume that we all have 4-bladed props(?).

-- John H

 

[PeteLam]

8 Knots at 3400 rpm...Peter