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Old 31-07-2014, 16:01   #1
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420 Props

We have 18 " 3 blade folding props on our 420 Diesel with Yanmar 3HJ4E stock 39HP engines. Performance is good but I'm seeing some sooting around the exhaust and am told that's because the engines are overloaded and the boat "over propped".

Full throttle is 2800 rpm but I'm advised that I should be seeing 3300 rpm. I use 2200 rpm for cruise power.

Also I'm advised that the clutch cone issues are not improved because the (Australian made) Slipstream 3 blade 18 " props continue to rotate after folding. The Gori prop dealer says that Gori Props do not do this.

Be interested in other owner experience.




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Old 01-08-2014, 06:22   #2
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Re: 420 Props

I have 18x15 flexofolds that reach full rpm on the 4JH4-TE (75hp) engine. You didn't say what pitch you had on your props.
My will also rotate under sail initially but putting the engines in reverse (after they are stopped of course) for a couple seconds stops the rotation and the props fold. Then I shift back to neutral and they won't start rotating again until I start the engines.

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Old 02-08-2014, 03:58   #3
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Re: 420 Props

My props are 18 x 13" . Finer pitch, so in comparison to yours I should be getting more revs I guess.


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Old 02-08-2014, 04:36   #4
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Re: 420 Props

I have a Lagoon 400 catamaran with 2 Yanmar 3JH5CE engines and 2 Yanmar SD 60 Saildrives. Theyre 39HP and the max revs is about 3200. We have been running the engines in so have been operating them at 2800 RPM mostly which gives a crusing speed of around 7 k on one engine. Props are folding 3 blade flexfoil. Fuel consumption is around 3.75l/hr at that speed. Id like to make a consumption/speed/range/revs spreadsheet if anyone else can fill in more estimates/details would be great.
Something like the one here.

Twixter -* Performance

Heres the details for our last boat.
Fuel capacity: 2 x 110 Liter tanks (Diesel)


For trip planning purposes (Conservative), each engine burns approx 2.1 Liters of diesel per hour @ 2100 RPM, which gives up to approx 52 Engine hours per engine per tank.


One engine @ 2100 RPM gives approx 4.3 kts of speed in calm water, which gives approx 234 nautical miles per tank using one engine.


2 engines at 2100 RPM gives approx 5.5 knots

Sephina

2 x 100l tanks + 2 x 20l reserve jerrry cans

3000 revs one engine 7k 3.3l/h range 30 hrs/tank 210 miles /tank

2200 revs one engine 5.5k
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Old 12-08-2014, 04:46   #5
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Re: 420 Props

Hi Monte,
Interesting figures. Are they your measurements or calculated from fuel consumption graphs? I have 3JH5Es with Flexofolds and seem to burn a bit more fuel at max cruising revs (2800 rpm). I like to run these revs to load the engines for longevity reasons as puttering at the economical 1800 revs all the time can (may?) induce coking or glazing issues.The Yanmar graph indicates 6 lph at 2750 rpm. A lot more than you say you burn.
I am thinking fuel flow meters would be a good investment.
Enjoy your trip. Cheers
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Old 12-08-2014, 05:28   #6
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Re: 420 Props

yes id be interested in some real world figures as well. its a bit hard to calculate when time is spent at lower revs docking, sialing etc. However our first 40 hrs running time we used 150l of fuel per engine, mostly running at 2800 RPM. Distance traveled was 430M at average speed of 7 K.
from those figures it seems 300l will take us 430M@7K 2800RPM (61 hours)
so burn rate is 5 l/h. Most of that motoring was with little wind (no strong headwinds, but sometimes motorsailing) so that may account for the 1 l/h less than the yanmar graph. Ill experiment with the different RPM's as well as trying both engines at the same time to see what the most economical option is.
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Old 13-08-2014, 05:01   #7
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Re: 420 Props

As a heads up, the tachs for the Yanmars were junk from 200? to 2012. They just started with a new supplier last summer. I had one tach fail outright May 2013 and the other May 2014 (2009 mfg date). What I learned is the olds tachs were off by ~200 and ~400 rpm. Not just a little off. So you may want to check their accuracy as you are doing your measurements. My new ones were quite accurate when installed.

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Old 15-08-2014, 20:26   #8
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420 Props

Seaqul, I suspect you are right about the tachos. The Yanmar instrumentation (I have the std Type B - no gauges) and the hour meters work about 10% of the time. And my port tacho sometimes reads full scale, sometimes nothing. Who knows how accurate they are? I have in mind checking the actual revs when I can.

Why did you change your tachos? Granted they are poor but I set the power more by sound/ feel than numbers so while it would be nice to have an accurate reading I don't know if I would go to the trouble of changing them.



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Old 16-08-2014, 05:27   #9
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Re: 420 Props

The first tach lost tach then light then hours (I limped along as you say with just the hours until it died) so I either had to change it or add an hour meter. Decided to change so I had a reference. Very easy to swap out, four screws and pull the plug.

As you, I also run mainly by ear, especially syncing the engines, but for those long cruises, it was cheaper to have one accurate tach than to put in fuel flow if you are managing a tight diesel budget. When the other tach finally went completely out this year I decided that for resale (still a ways off I hope) it was probably best having both operating and a complete hours history. And with the tach price slightly over $200, it made sense to just install new. New ones have a red light (not white) so are nice at night and it is a pleasure to see everything again. Also, my first mate doesn't do so well with the ear thing so when she is on duty (half the time on the long trips, we do 3 on 3 off) and the winds are down, she has no problem managing the engines to a number.

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Old 17-08-2014, 12:11   #10
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Re: 420 Props

A quick question. We have the new tachos and yanmar 39hp, but the tacos only display hours and revs with warning lights for temp, pressure etc. is ther a way to utilise the tacos to show actual temperature etc? The facility is in the tacos, but I guess they aren't hooked to the engines or the engines don't have that facility..
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Old 18-08-2014, 17:48   #11
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Re: 420 Props

Paul, thanks for the info. I see your point.

Unfortunately we would probably pay 2 or 3 times the price for Yanmar parts here. You can buy online in the States but suppliers are not permitted to ship outside the US.


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Old 19-08-2014, 06:14   #12
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Re: 420 Props

Bob,

Understand the pricing dilemma. Faced that as well in the Caribbean and waited until I was able to get back to the States.

Monte,

The tach you mention is for the newer model B20 panel and is more expensive because it has all the instrumentation display. I assume you have a newer B20 panel? If so, the wiring harness has yellow/black (oil pressure) and white/black (water temp) wires running between the tach and the senders on the engine (not there on older B model panel hookups). You should be able to see these values on your display unless the senders weren't installed on the engine. The right button on the tach should scroll between hours/coolant/brightness/oil/battery and back to hours in order to see the values.

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