MBY March - Article "Time to Reflect"

Billy Blue

Billy Blue

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In this article in which the owner reflects on 3 years of owning his Antares 8, I was surprised to see his comment "However the speed does limit my range as technically I should not run the engine at more than 35% load for extended periods, which basically means I should run displacement mode for anything more than a 10 mile passage."
My immediate thought was "Surely this can't be right" but in fact I really don't know so I'll let people who do know educate me.
The engine is a 200hp Nanni diesel.
 
I'd concur with you. The owners manual mentions nothing about that. Quite the opposite.

It says "The recommended cruising speed is 200 rpm below the maximum rpm speed at full throttle"

google : "Notice de conduite M1KD ENG.pdf"
 
"I read that too. Seems a shame that he’s had it 3 years and is afraid of using it if this is true."

That was my thought as well.

I should have put the next sentence perhaps as well, following "However the speed does limit my range as technically I should not run the engine at more than 35% load for extended periods, which basically means I should run displacement mode for anything more than a 10 mile passage."
which was
"This reiterates the point that Greyfin is an ideal boat for messing about locally rather than passage making and I'm happy with that."
Hopefully, this new revelation will open up his horizons for him.
 
That aside, it sounds like he’s dead chuffed and it’s a great boat. I’m hoping to get my mf805 this week and this is just enthusing me more.
 
haven't read the article, but the only think I can imagine is that he's confusing the engine duty as designated by the company with use patterns, I agree rather pointless. You know the one that makes the same block rated as heavy duty at 200hp and whatever it's called for us duty at 400hp or so :rolleyes:
Which probably says somewhere in there that you cannot use WOT for more than 35% of the engine hours operated, where as in the heavy duty rating for this motor which will probably by under 100hp you can, Assassin or others?

cheers

V.
 
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Each engine manufacturer should have their rating definition and accepted usage published somewhere for the given engine series ...... here from FTP ...

A1= High performance crafts: Full throttle operation restricted within 10% of total use period. Cruising speed at engine rpm <90% of rated speed setting - Maximum useage 300 hours per year.
A2= Pleasure/commercial vessels: Full throttle operation restricted within 10% of total use period. Cruising speed at engine rpm <90% of rated speed setting - Maximum useage 1000 hours per year.
B= Light duty: Full throttle operation restricted within 10% of total use period. Cruising speed at engine rpm <90% of rated speed setting - Maximum useage 1500 hours per year.
C= Medium duty: Full throttle operation <25% of use period. Cruising speed at engine rpm <90% of rated speed setting - Maximum useage 3000 hours per year

For those of us with older engines, there will be different criteria ... as ours for instance... they are rated at WOT 2300 RPM and fast cruise is defined as 2100 RPM ... However, there is a rider in there stating that for "longer continued operation" (defined as operation is exceeding 10 hours continual load), then the recommendation is to operate the engines at 1850 RPM...
 
I do think that this misunderstanding should have been picked up before it was published. Now it is in black and white, it could mislead others.
 
KDeacon62 said:
What about Antares 8 outboard with Suzuki 200HP? What is a sensible cruising speed/rpm for say 4-5 hours?
Click to expand...
As long as your not WOT for 5 hrs I don't think there are hard and fast rules. It's your boat your engine, you use it the way you are comfy with. If it were me I'd be WOT until on the plane then throttle back but still staying on the plane. Use your trim tabs if you have any and trim your engine correctly.
At the end of the day you should drive the boat at a speed that suits the conditions and your own comfort.
 
KDeacon62 said:
What about Antares 8 outboard with Suzuki 200HP? What is a sensible cruising speed/rpm for say 4-5 hours?
Click to expand...
Completely different ball game running a petrol at any load .Fill your boots , your tacho has a redline note it and stay under .
Any hrs any rpm under the redline .

This is because of a few factors , the difference between a marine diesel , note the term marine ( drop any car / truck thinking *)
The difference in cylinder temps / pressures of diesel being far higher to ignite none volatile oils as opposed to petrol fumes .

So the rings of the Honda are pretty tight when cold and hardly anything gets past them , nothing when at running temp .

The rings of your diesel are loose and when cold basically leak , even at pootling / low rpm s they don’t fit properly so that’s why your oil turns black , they smoke when cold due to oil getting past and products of combustion getting into the oil .That’s why the oil change Fq is more critical in a D .
At the correct cylinder temps / pressures the EGTs ideally should be 550-650 *c ball park .Everything is sealed the thing is running optimally .
This is where the 80 % load or if load delta is nit available on your dash the Hand book 200under WOT .

The prop ( unlike a car which had a gear box to select a ratio ) is effectively TOP gear .Your D boats running around in top all day .
Arguably with fouling up a ever increasing hill gradient .

When the Honda is a bit fouled , or the boat a bit heavy the temps in the petrol cylinder hardly rise as remember petrol is explosive/ volatile etc - the ECU just adjusts the fuelling .Even so iirc we are talking circa 300 *c so even if it rises to 400 or 500 which it doesn’t the Honda petrol can cope .

Mean while back in D land , marine remember not your car / truck , that bit of fouling of the prop / hull or excess weight causes the pump to attempt to squirt more fuel into the already hot cylinder .
D engines are demand driven unlike P engines .
This extra fuel increases the cylinder T + P s massively to potentially dangerous levels .AND instantly.So you do not see it on your 84/85 Water jacket gauge ,
The term is overloaded .
The “ load “I am referring to is the pumps % to meet the demand .
The EGT s soar towards 1000*c and load over a 100 %
So what I here you say ? …….the exhaust valves mushrooms and the E manifold , and turbo bearings “get it “
D engines are robust so may not notice the reduced power of mushroomed valves .
The injector tips are harmed and the spray pattern deteriorates , Todays common rail micro canalised injector tips probably harmed easily or burn off leading to hosing .

Single tip old fashioned like on a Gradner 6XLB less so hence the legendary reliability etc etc .

Manufacturers do indeed publish the duty cycles and % time at what loads .
As this was the reason of this thread it’s worth researching ( the correct data mind ) and adhering .

Having said that some of you can’t access load or EGT s .From circa 2000 they started to introduce that tech in to leisure.
BTW German u boats had EGT gauges ( 1938 up ) on each cylinder of there MAN diesels .
 
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