Yanmar 3YM20 vs Beta 20

[FlyingScot]

Originally Posted by Cheechako

Compare RPM vs HP curves also. Yanmars are famous for rating at high rpm, thus making a lower HP engine appear to be higher HP. (Well... that's one way of saying it) I don't know about the Beta. I hated running my 3600 rpm Yanmars at 3400 rpm.

Both are rated at 3600 rpm.

[bounty hunter]

Originally Posted by FlyingScot

I don't see that in the specs.
Yanmar 21bhp vs Beta 20bhp. If you referring to maximum continuous power, Yanmar doesn't allow continuous full throttle operation either. This model seems to want 100 rpm less. My 3YM30 wants 200 rpm less.

no i wasnt so much referring to the manufacturers maximum recommended continuous load - i was just pointing out something which i hadnt seen in earlier comments in the thread - and that was whilst both Yanmar and Beta's model designation suggests theyre both '20hp' - when making an 'apples-apples comparison', that the manufacturer supplied documentation tells a different story.

Yanmar docs show their motor outputting a maximum of 21 metric hp when measured under ISO8665 conditions;

https://www.yanmarmarine.com/theme/y...heet_3YM20.pdf

Beta's 'headline' number is 20hp - but if you take a closer look at the specs they publish here;

https://issuu.com/betamarine/docs/b2...14309/68213453

youll note a second - and lesser - output curve as measured at ISO8665 - which shows only about a maximu of 17mhp being produced - from this curve you can also calculate out that torque production is similarly slightly lower than the Yanmar engine

[Cheechako]

Originally Posted by FlyingScot

Both are rated at 3600 rpm.

OK, take a look at the HP curve and how do they compare on the way up to 3600 rpm. Does one develop more HP earlier? etc

[FlyingScot]

Originally Posted by bounty hunter

no i wasnt so much referring to the manufacturers maximum recommended continuous load - i was just pointing out something which i hadnt seen in earlier comments in the thread - and that was whilst both Yanmar and Beta's model designation suggests theyre both '20hp' - when making an 'apples-apples comparison', that the manufacturer supplied documentation tells a different story.

Yanmar docs show their motor outputting a maximum of 21 metric hp when measured under ISO8665 conditions;

https://www.yanmarmarine.com/theme/y...heet_3YM20.pdf

Beta's 'headline' number is 20hp - but if you take a closer look at the specs they publish here;

https://issuu.com/betamarine/docs/b2...14309/68213453

youll note a second - and lesser - output curve as measured at ISO8665 - which shows only about a maximu of 17mhp being produced - from this curve you can also calculate out that torque production is similarly slightly lower than the Yanmar engine

Good catch.

Originally Posted by Cheechako

OK, take a look at the HP curve and how do they compare on the way up to 3600 rpm. Does one develop more HP earlier? etc

The Beta is a little smaller in displacement so I suspect the Yanmar makes more power through most of the rev range. Especially when accounting for what Bounty Hunter mentioned with the power ratings.

[Uncle Bob]

Originally Posted by ramblinrod

The Yanmar 3YM series incorporates common rail EFI technology. Vastly superior in efficiency, reliability, and emissions reduction. You will not see black soot from the exhaust of one of these engines, coating a white transom, even if overloaded (poor prop selection).

Originally Posted by FlyingScot

Both the Yanmar 3YM20 and the Beta 20 are indirect injection.
http://www.betamarineengines.com/dow...C-SOM-0314.pdf
https://www.yanmarmarine.com/theme/y...heet_3YM20.pdf


I would not want common rail on a sailboat. The increased efficiency doesn't offset the complexity and increased difficulty of service.

Well, which is it, common rail or not. You cant both be right.

[Wotname]

Originally Posted by FlyingScot

Both the Yanmar 3YM20 and the Beta 20 are indirect injection.
http://www.betamarineengines.com/dow...C-SOM-0314.pdf
https://www.yanmarmarine.com/theme/y...heet_3YM20.pdf

I would not want common rail on a sailboat. The increased efficiency doesn't offset the complexity and increased difficulty of service.

FWIW, the Beta documentation shows it to be a traditional mechanical injection system while ramblinrod tells us the 3YM series are common rail EFI. I assume he is correct!

A common rail EFI would be a deal breaker for me!

Originally Posted by ramblinrod

The Yanmar 3YM series incorporates common rail EFI technology. Vastly superior in efficiency, reliability, and emissions reduction. You will not see black soot from the exhaust of one of these engines, coating a white transom, even if overloaded (poor prop selection).

[bounty hunter]

Originally Posted by Uncle Bob

Well, which is it, common rail or not. You cant both be right.

RablinRod s statement that the 3ym is 'common-rail' hp injection is incorrect - a quick look at the Yanmar website confirms this

[a64pilot]

Originally Posted by Cheechako

OK, take a look at the HP curve and how do they compare on the way up to 3600 rpm. Does one develop more HP earlier? etc

You can’t break out Tq and HP separately. I know everyone tries to but they are interrelated.
Torque is a twisting moment, but no movement, RPM is of course speed. Torque times RPM x a constant 5252 is Horsepower. Decrease either torque or RPM and HP goes down, increase either or both and it goes up.

If you look at any dyno chart that the engine makes 5252 RPM or higher, you’ll see that the HP and torque curves cross at exactly 5252 RPM, if they don’t then the graph has been doctored, which happens more than you might think.

Then to further complicate things, it wouldn’t matter if one did make more power down at a lower RPM, unless it was a HUGE difference.
The reason is the propellor will only use so much HP per RPM, so if you prop an engine correctly, that power that it’s capable of making at low RPM won’t be used, cause you only pick a prop that matches engine output at one RPM, that being it’s max RPM, so at any RPM less than max the engine is capable of producing more power than the prop will accept.

[Uncle Bob]

Originally Posted by bounty hunter

RablinRod s statement that the 3ym is 'common-rail' hp injection is incorrect - a quick look at the Yanmar website confirms this

Oh heaven forbid no, RamblinRod incorrect , and him being a certified Yanmar dealer and all!!

[skipmac]

Originally Posted by ramblinrod

Clean air and fuel is important to every ICE on the planet. I don’t believe there is any difference in sensitivity between common rail and cam driven pumps, an injector orifice is an injector orifice. How the injector is driven has no connection to the fuel supply IMHO.

Actually it makes a big difference. Common rail systems are much more complex and are quite different from an old style, mechanically driven injection system.



https://www.sae.org/publications/tec.../2010-01-2242/



To meet increasingly stringent diesel exhaust emissions requirements, original equipment manufacturers (OEMs) have introduced common rail fuel injection systems that develop pressures of up to 2000 bar (30,000 psi). In addition, fuel delivery schemes have become more complicated, often involving multiple injections per cycle. Containing higher pressures and allowing for precise metering of fuel requires very tight tolerances within the injector. These changes have made injectors more sensitive to fuel particulate contamination.

[Dockhead]

Originally Posted by Q Xopa

Im sure Rod or someone else can correct me, but I hear (unsubstantiated), that the Yamnar engines are 'recreational' rated, where as the Kubotas are 'argricultural/ industrial' rated. Which relates to their 'duty cycle'. Ie Industrial rated at higher loads for a greater proportion of their life than Recreational rated engines, that are not intended to be as abused, as much of their lives.

There is no such thing as "industrial rated"


With marine engines, "recreational rating" only refers to the rated power. The very same engine may have different rated power depending on whether the power is used continuously or not. Hardly relevant to us since in a sailboat you will very rarely use full power and never for extended periods of time.



Yanmar and Kubota both very durable, very good, Japanese engineering made by companies with huge engineering resources and a century, give or take, of experience building millions of diesel engines.

[Dockhead]

Originally Posted by bounty hunter

RablinRod s statement that the 3ym is 'common-rail' hp injection is incorrect - a quick look at the Yanmar website confirms this

Indeed. He's confusing the 3YM with the 3JH40. 3YM has mechanical fuel injection using the classic Zexel injection pump:

[Wotname]

Originally Posted by bounty hunter

RablinRod s statement that the 3ym is 'common-rail' hp injection is incorrect - a quick look at the Yanmar website confirms this

Originally Posted by Dockhead

Indeed. He's confusing the 3YM with the 3JH40. 3YM has mechanical fuel injection using the classic Zexel injection pump:

Attachment 202954

Two posts stating the 3YM series have old style mechanical injection (and a picture which has to be be worth a thousand words) - just need confirmation of this from a Yanmar dealer and the question will be settled for once and for all

[Compass790]

Originally Posted by Wotname

Two posts stating the 3YM series have old style mechanical injection (and a picture which has to be be worth a thousand words) - just need confirmation of this from a Yanmar dealer and the question will be settled for once and for all

How any Yanmar dealers would you need to canvass?

[Dockhead]

Originally Posted by stormalong

. . .I don't know which Yanmar it is but one of their "marine" diesels requires the removal of an engine mount to change the raw water impeller.

Probably the result of a badly conceived installation, but I have heard of this, so must not be a one-off situation.


Many Yanmars, including my 4JH3 HTE, have the water pump">raw water pump in a very awkward position. This is because the raw water pumps are GEAR DRIVEN, rather than belt driven.


Mine is awkwardly mounted right in front of the starter motor, so close you can't get an impeller puller in there, and if you forget to shut off the sea cock before removing the impeller cover, you've just bathed your starter in seawater (don't ask me how I know ).


But gear driven is really nice, plus being right at the bottom of the engine, they are always full of water, so leaving a sea cock accidentally shut or getting seaweed in the strainer doesn't destroy the impeller.



There are pluses and minuses, so you pays your money and takes your choices!