R-21 EC RPM Survey

[Rick & Karen]

Good Morning Everyone,

I have been reading with interest the ongoing discussion about the Yanmar factory specs versus actual RPM and I am wondering what other R-21 EC owners are seeing on their tachs. A week ago I had my mechanic come out to the house and give Kolo Iki's engine a thorough going over, to include an initial valve adjustment, fuel filter change, coolant flush and fill, oil change and filter and a new impeller. The engine had 131.0 hours on the Hobbs, but the boat was first put in the water in the spring of 2007 and I wanted to re-index everything to a known reference point. Basically, I did a slightly early 150 hour check. It was the third oil change for the engine and I had changed out the transmission oil a couple of months ago. For the moment, I should have no routine maintenance worries until next summer.

Which leads me to my question about RPM. My engine will go to 3800+ RPM in neutral, so I know that the throttle cable linkage adjustment is fine. When running the boat, the max RPM I see is about 3300. In fact, I don't ever recall anything much above that, although it is possible. I keep the bottom clean by frequent dives, but there are a few barnacles on the prop. The original factory fuel filter looked almost new when replaced and I have purchased a RACOR fuel filter to act as the primary filter, but it has not been installed yet. Like many owners, my normal cruise operating range is 2400 to 2800 RPM. About the only reason I see to operate in the low 3000 thousand range is to exercise the engine and to prevent carbon buildups. I find that the bow rises along with the noise level as the little tug hunkers down, but the speed increase is negligible.

In short, I think Kolo Iki is operating in her normal loaded RPM range, despite what Yanmar has stamped on the engine data plate. In another post, Andrew was quoted as saying that Yanmar told him that 3200-3600 was an acceptable RPM range under load. That falls within the range I have observed, but I would be very interested to hear what other R-21 EC owners have to say on this topic. Mahalo for your input.

Aloha,

Rick

 

[rt11002003]

Looks like I weigh in again on this subject to put the input in one thread. Yanmar says the engine should turn 4000-4400 rpm max with no load. They say it should always be capable of pulling 3600 rpm under load, they recommend propping at 3800 rpm to allow for additional load.

Andrew and Jeff have both told me that Yanmar, in working with them to find a suitable prop for the boats, said 3200 to 3600 rpm under load was OK. I'd be happy with that, iff Yanmar accepted that should there be any warranty claims. Andrew said he'd have the Yanmar person talk with me. Nothing yet from Yanmar.

My max rpm without a load, ie. no prop effect, has always been 4000 rpm. Initially, my max rpm under load, ie. prop effect, was 3375 rpm. I had primary fuel filter clogging and the rpm dropped to 3200 and then to 3000. Changed filter and rpm is now barely 3300.

I prefer cruising at lower rpm; the tug is much more pleasant. I'm still in breakin, so I'm following the Yanmar manual, running the engine at much higher rpm than I like, about 2800 min, some 3000 and hourly runs of five minutes of max rpm. I'm also doing the five cycles of wide open throttle.

The engine seems to run fine and is reasonably quiet for a diesel. However, I think the alternator or the transmission/clutch assembly is really loud; it/they howl(s). At certain rpm it's almost deafening.

Engine box setups are noisy. I also think sound bounces around thru the bilge. I'm considering trying to insulate the area under the engine with something like "SounDown". I met a fellow last Fall who had supervised the building of his Marine Trader 38. He lined the the engine compartment with lead. It was quiet.

Gene

 

[K7MXE]

I cant be much help on max rpm because Its rare when I get it up to 2600 and have lot left to go but one thing you said has my attention. Barnacles on the prop will load things down a bunch and puke out black smoke too. I learned that from my sailboat days plus the poor old sailboat could not get out of its own way. I backed the sailboat up to the beach and got under there with a paint scraper and that worked for me. Do that first and see if the rpms dont change somewhat.
Bob Heselberg

 

[Rick & Karen]

I cant be much help on max rpm because Its rare when I get it up to 2600 and have lot left to go but one thing you said has my attention. Barnacles on the prop will load things down a bunch and puke out black smoke too. I learned that from my sailboat days plus the poor old sailboat could not get out of its own way. I backed the sailboat up to the beach and got under there with a paint scraper and that worked for me. Do that first and see if the rpms don't change somewhat.
Bob Heselberg

Hi Bob,

I had the prop cleaned by a diver with a tank a couple of months ago because it was more than I could do with a snorkel. At the time I was running about 3200 RPM at max throttle and I noticed an increase of about 100 RPM after the cleaning, so I hear you. It was a bit of an eye opener for me. On the plus side, I have never had any black smoke 🙂

Where I usually clean the boat, the water can be quite murky and it makes it hard to see what you are doing. If I go out past the surf break the water is crystal clear, but we have been hit with a south swell the past few weeks and the water has been rougher than I like for working around the hull and running gear. I have found a website that sells special equipment (gloves, helmet, hand tools) for boat cleaning and I am seriously considering making a purchase. The helmet looks like a wrestlers helmet and is designed to protect your noggin from bouncing off the hull or other hard parts when underneath the boat. Having made contact a time or two, I can see the value of that.

I know that if I do not try to catch up with the prop soon, I will have to pay to have it cleaned again. I am amazed how fast marine growth sprouts in warm tropical waters. As always I appreciate your input and by the way, a big mahalo for including the link to the Yanmar service manual. It is now an icon on my computer desktop and it came in handy during my service call a week ago. The service manual fills in many of the blanks that are not addressed in the owner's manual.

Aloha,

Rick

 

[rt11002003]

Rick,

I forgot this tibit. I think it was the owner of Hunt Associates, who said well designed boats should run with the bow out of the water. The factory photo of a R-25 shows it running bow out.

Have any of you seen the R-21 EC running at various speeds and noticed how it sat in the water? I'd like to observe that.

Gene

 

[Rick & Karen]

Rick,

Have any of you seen the R-21 EC running at various speeds and noticed how it sat in the water? I'd like to observe that.

Gene

Hi Gene,

Kamalani's main album photo shows the bow out of the water at cruising speed. I have a friend out here that just bought a used 21 footer cuddy cabin powered by a Mercury outboard. Unfortunately he is having a lot of problems getting everything to run right. When he does, we are going to get together for an underway, offshore photo op. I would love to see Kolo Iki from a distance doing what she was designed to do. Photos to follow when available.

Aloha,

Rick

 

[Rick & Karen]

Hi Everyone,

So far Gene and I concur that 3300 RPM seems to be about the max RPM observed for our respective R-21 EC tugs. That appears like it might be a normal top end for at least some of the little tugs. What say the rest of you R-21 EC owners who post on this board. Is anyone seeing 3600 RPMs on their tach? I'm okay with a 3300 RPM top end, but I would feel better if were fairly common and not an anomaly. Standing by for input.

Aloha,

Rick

 

[gunterprof]

Orion from day one has indicated a maximum of 3250 RPM on the tachometer. Since the problem of engine surge has begun we are only indicating a maximum of just over 3200 RPM.

Dan

 

[johnniethek]

I'm in the 3250 RPM range for the Red Ranger. Of course, I only have about 35 hours on her. I will test it out again next week when I spend it in the San Juans, and will report back if there's any major change.

 

[rt11002003]

Dan,

Have you changed the primary fuel filter? Changing it stopped my surging.

Gene

 

[gunterprof]

Gene,

Thank you for the suggestion; have tried that in the past. Orion is a 2008 model and has only the one fuel filter mounted on the engine. I have changed it twice. Neither time that I changed the filter did I find any contamination. Still have the surge situation.

Dan

 

[rt11002003]

Dan,

Sounds like it could be an air leak then. With diesels the problems are usually fuel, or fuel related. You might start looking for air leaks. The best way to start is to get a container and put a couple of gallons of fuel in it. Disconnect the fuel suppy and fuel return lines from the engine. Install temporary lines from the container to the fuel inlet and to the fuel return on the engine. Make sure you secure these items to the boat so that nothing can move and spill fuel. Operate the engine. Bleed the air per the manual. If running the engine from a temporary fuel supply eliminates your surging, the problem is somewhere in the supply side, including tank fittings. Look at connections and lines. It could be as simple as a loose hose clamp, a pin hole in a line or even a cracked fitting.

If the temporary fuel supply test doesn't stop the surge then you have a problem is in the engine side, pumps, injectors,etc. And, also maybe in the supply side since it hasn't been eliminated.

Gene

 

[gunterprof]

Gene,

Again, appreciate your suggestions. Next week will give the air leak idea a try.

Dan

 

[Shaun]

The Rub N Tug has just over 420 hours on her, most of which are open ocean at 2800 rpm, and the most I've ever seen under load was 3200 rpm. I feel there is no need to run her up past 2800 because all you do is burn more fuel with little to no more speed. The 3ym30 stops making horse power at 2500 and the tourqe stops shortly after that. Shure she can run higher but with what to gain.

 

[rt11002003]

For those who might have missed my initial post about this subject.

My concern about the 3600 rpm was because the Yanmar manual stressed it and in the next paragraph brought up the warranty issue if one didn't comply with Yanmar standards.

I'd prefer a slow turning engine, on the order of 2000 max rpm, with a cruise rpm of maybe 1500 rpm. Of course, I'd like a cruise speed of 10 knots at 1/2 gallon per hour to go with that 1500 rpm. 😀

Gene

 

[Rick & Karen]

Many thanks for everyone's input. It would appear that we are all playing from the same sheet of music and 3200-3300 RPM seems to be where the typical R-21EC model hits the wall. That is perfectly fine with me as I don't like to spend much time there anyway, I agree wholeheartedly with Shaun's (Rub N Tug) observations. I just wanted to make sure that there was nothing I needed to check as to why Kolo Iki was not turning 3600 RPM.

Aloha,

Rick