Max Cruising RPMs for Yanmar - Page 3 - SailNet Community
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post #21 of 36 Old 04-09-2008
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Quote:
Originally Posted by hphoen View Post
Ditto, but I'd add another--soot buildup in the mixing elbow (where the exhaust gases cool down). Get enough in there and the engine falters.
That is the #1 first thing I look at when I don't have good flow out my tailpipe.

(#2 is the impeller)

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post #22 of 36 Old 04-09-2008
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My manual for the 3ym30 I installed recommends cruising rpm of 3200rpm, and have done this for the last 750 hours, with ill effects, as well have fined tuned the valve adjustments as well the injection timing and have even a more cleaner burn engine. All oil samples thus far have shown nil engine wear.

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post #23 of 36 Old 04-09-2008
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Carbon Buildup

Quote:
Originally Posted by hphoen View Post
Ditto, but I'd add another--soot buildup in the mixing elbow (where the exhaust gases cool down). Get enough in there and the engine falters.
Please correct me if I am wrong.

Carbon buildup is BAD. I noted earlier that it was said that you just punch it every once in a while and clean it out. My undersatnding, although there is some fact to that, is not entirely the same.

The mixing elbow was mentioned so I will start there as I have had to deal with high backpressure issues (not on my boat) - but seemed to have gotten quite an education.

If you are getting high back pressure, the rear cylinders will get hot. You will also get a carbon buildup in those cylinders. That carbon then slowly scores the cylinder walls. That in turn causes a compression loss. Compression loss then causes engine performance loss and finally total failure.

That is why you do not run your engine for long periods of time at low RPM's. Please explain where I am wrong. THis is what has been explained to me by Mastery, Boatswain, Yanmar, Valiant, and many other marine engine specialists that had to get involved. In essence, it is the reason that running your engine without a load is a bad idea - carbon buildup.

One of the key tests for a diesel's health is a compression test. Each of the cylinders should be within 10% (depending upon the engine) of each other. If they are not, there is an issue somewhere. I know that we found many rear cylinder failures due to carbon buildup due to a mixing elbox without the proper sized exaust tubing.

Again, I do not pretend to be a diesel mechanic, just repeating what I have learned and been told over the years. Carbon buildup and cylinder scoring is like diesel cancer, a slow, quiet killer.

Thoughts?

- CD

Just an edit and feel fre to jump in: Not running at a load causes the cylinders to not have the proper backpressure and will cause scoring.

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post #24 of 36 Old 04-09-2008
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rear cylinder carbon would be an issue if the fuel system was fed from a central system like in a carburated engine, but being a diesel engine has individual injectors, there should be a constant fuel and air supply to each cylinder. The main issue is constant maintenance. Your doctor does blood testing to know your body and its internal issues. Oil testing does the same and warms of pending issues. This is not expensive at all.

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post #25 of 36 Old 04-09-2008
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Taronga - 4JHDTE (1991) - runs at 2,800. This older version smokes more than the newer ones (according to mechanic and Yanmar) but with the right compression we still are running clean, the elbow is clear and not using much oil. Injectors are worth checking every several years. Biggest issue we have is not running the engine under load for long enough periods of time.


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post #26 of 36 Old 04-09-2008
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on my 18 hp yanmar's i was told by yanmar to run at 90% power....3000-3100 rpms. no problems, no issues.
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post #27 of 36 Old 04-10-2008
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Quote:
Originally Posted by SVDistantStar View Post
I run the little 1GM in Lola about 3000-3100 most of the time. It doesnt use much fuel and seems to be nice and happy with that.
I'm curious to know your prop pitch, 2 or 3 blades and approx speed you're doing at 3100rpm on Lola. Thanks.

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post #28 of 36 Old 04-10-2008
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Just to echo previous advice ...

I spent all day Monday in a Yanmar seminar (Mack Boring); their guidance was to punch it for about 30 min every 10 hrs or so to blow the carbon out. "Punching it" under load meant, on the brand new 4JH's they had just delivered, the governor is set at 3300 rpm, the engine can go 3600. That's 5% of the total running time.

The other 90% of the time, 2800 rpm would get the boat to hull speed. The fuel consumption curves for this one were 1.3 gph @ 2800; and 2 gph @ 3300.

The last 5% - don't shut the engine down hot. Let it idle for 5 min or so to cool off first.
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post #29 of 36 Old 04-10-2008
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Quote:
This older version smokes more than the newer ones
jimmalkin,

i believe they told you this, but i think that smoke is factor of many things, and if the mechanic said it, that's one thing, Yanmar, they're smarter than that. Black smoke i think good...engine running under load, smoke is oil. White smoke i think fuel contaminant, i.e. water, tank growth.

And Ken you're right
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I'm curious to know your prop pitch
pitch is a factor to consider correct load at different RPM.

s/v Libertine
Hunter 44DS

Last edited by petegingras; 04-10-2008 at 04:46 PM.
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post #30 of 36 Old 04-10-2008
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If an engine is not a smoker all the time the smoke under load will be unburt fuel, as is the same in the Auto industry

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