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Old 09-01-2014, 11:21 AM   #1
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Wide Open Throttle

This is an extension of the minimum RPM thread.

Vashon Trawler wrote;
"I love your statement, Manyboats. So true! This has been an interesting thread. It is impossible for me to believe that occasionally running a marine diesel at WOT will cause damage.

I bring my diesel up to WOT in gear for one or two minutes at least once per month to ensure all is well and I can a reach my target of 3400-3600 RPM. I may be in an emergency situation where I actually need the HP; and, knowing my prop is pitched correctly (not under-propped), I can confidentially deliver full HP at maximum RPM! My Volvo Penta manual suggests not running WOT for more than 10-15 minutes as I recall, which is a long time in my book and this is probably conservative."



VT thank you and I think ...
" Volvo Penta manual suggests not running WOT for more than 10-15 minutes as I recall," ... is typical.

I've never run WOT for 10 minutes either but I'm sure I could w/o side effects or engine damage.
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Old 09-01-2014, 12:22 PM   #2
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If your engine is in good shape and correctly propped there are beneficial aspects of running WOT. Remember even a M4 rated engine is approved for something like 4 out of 12 hours at WOT. The WOT is a good test of propping and overload due to prop or fouling of bottom. WOT is also a test of engine health. If your boat cannot reach spec rpm something is wrong and should be corrected. A ten to fifteen minuet run at WOT will help clean out motor and exhaust will get rid of moisture and circulate lube oil. After running at low loads common on trawlers it is a good idea to go WOT at the end of the day or every few hours. When I travel I often cruise at 30% load and will push throttle up to high load for 10 min. at the end of every hour.
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Old 09-01-2014, 12:45 PM   #3
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If your engine is in good shape and correctly propped there are beneficial aspects of running WOT. Remember even a M4 rated engine is approved for something like 4 out of 12 hours at WOT. The WOT is a good test of propping and overload due to prop or fouling of bottom. WOT is also a test of engine health. If your boat cannot reach spec rpm something is wrong and should be corrected. .
Right on but ---

Unless of course you have intentionally over propped your vessel which prevents the engine from reaching full rated RPM

Some like Mr Calder get paid to write articles suggesting over loading has a place for the recreational boater. If all he said was "follow the manufacturers guideline" he would not have had that article published and worse yet not get any attention.
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Old 09-01-2014, 12:49 PM   #4
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eyshulman,
Indeed but some are afraid. Many w no good reason and some w good reason. The latter should fix their boat and the prior should buck up. I used to hate that expression "buck up". I told Tom White as much a few years ago .. Haha. What you say is the right thing to do but they are our boats and we can do as we wish.

Running at WOT gives me more confidence (assuming all goes well) and after some engine running problems confidence seems good. I'm going to be looking for it soon after we launch.
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Old 09-01-2014, 12:55 PM   #5
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We typically run at WOT a few times a day for 5 to 10 minutes and then pull back to cruising speed. It gives quick data as to how the engine is performing plus we just enjoy it.
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Old 09-01-2014, 12:56 PM   #6
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Running at WOT is essential to determine if one's props are pitched, tuned, and balanced properly. The WOT rpm of each engine with the existing props was something the prop shop that reworked the props required.
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Old 09-01-2014, 01:01 PM   #7
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"Running at WOT gives me more confidence (assuming all goes well) and after some engine running problems confidence seems good."


Exactly. This whole "you can/should never run your engine up to max rpm for a short time or you'll soon regret it" school of thought is bazaar.
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Old 09-01-2014, 01:08 PM   #8
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A short time (five minutes is the time I was told) is fine if you have to do it. Where the engine can have problems is if this is done a lot or for long periods of time.

What I find bizarre is people thinking that an engine designed in the 1950s can be operated in the same manner as a modern technology engine.

That's like claiming a Ford Model A pickup can be driven as hard and at the same speeds with the same loads as a 2014 Ford F-150. People in this "all engines are created equal" camp don't know much about engines in my opinion, and I would never act on their opinions or recommendations.

Instead, I would seek out people who truly know the engine in question and learn from them. Which is what we did in the case of the Ford Dorset/FL120. What I have been writing about the FL120 is simply parroting what we've been told by people with an intimate knowledge of these engines, particularly people we've become acquainted with in the UK.

This is the only diesel used in marine service we have done this for as it's the engine in our boat. I have no clue about the good, bad, or indifferent qualities of any other type of marine diesel.
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Old 09-01-2014, 01:45 PM   #9
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"Running at WOT gives me more confidence (assuming all goes well) and after some engine running problems confidence seems good."


Exactly. This whole "you can/should never run your engine up to max rpm for a short time or you'll soon regret it" school of thought is bazaar.

I think it extends from the logic of some newer owners of older boats. I've noticed some folks, not many, buying a 25+ year old boat expecting to just turn the key and run it on the pins for long runs. Then wondering why the boat doesn't perform the way it did when looking at the 25 year old sales brochure they found on Google. Or more often wondering why stuff is breaking more often than they think it should. Never once thinking of all the weight that boat gained since leaving the factory.

Californian 34's with Cat 3208's come to mind here, the sales literature claims 20 knot speed and shows pictures of them running that. Now go buy one and try it with tired 25 year old systems, a dirty bottom, poor previous maintenance and every cabinet stuffed to overflowing and full tanks and see what you get. It ain't gonna look like the picture of the empty boat cutting across the flat calm harbor with 1/4 fuel load in the photo op.

There's a vast gulf between short WOT runs and running on the pins all day long. One causes no harm and the other is going to require a platinum Visa card.
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Old 09-01-2014, 02:06 PM   #10
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Most captains here probably have semi-planing, my full displacement trawler knows only two speeds:
Idle (580 RpM ) or cruisingspeed (1700 RpM)
For those cruising speed is calculated the propeller and these speed runs the Supertramp since 1985 and i hope the next 100 Years too
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Old 09-01-2014, 02:59 PM   #11
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Except for emergencies there are three reasons to run pleasure rated engines at WOT for a minute or so. Test engine, hull and running gear, test the cooling system, spend money and be stupid.

How may would be happy to have their car tested at wot for 15 minutes? what would it prove?
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Old 09-01-2014, 03:10 PM   #12
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Californian 34's with Cat 3208's come to mind here, the sales literature claims 20 knot speed and shows pictures of them running that. Now go buy one and try it with tired 25 year old systems, a dirty bottom, poor previous maintenance and every cabinet stuffed to overflowing and full tanks and see what you get. It ain't gonna look like the picture of the empty boat cutting across the flat calm harbor with 1/4 fuel load in the photo op.
Here's what that looks like...compliments of chc!

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Old 09-01-2014, 03:15 PM   #13
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A short time (five minutes is the time I was told) is fine if you have to do it. Where the engine can have problems is if this is done a lot or for long periods of time.

What I find bizarre is people thinking that an engine designed in the 1950s can be operated in the same manner as a modern technology engine.

That's like claiming a Ford Model A pickup can be driven as hard and at the same speeds with the same loads as a 2014 Ford F-150. People in this "all engines are created equal" camp don't know much about engines in my opinion, and I would never act on their opinions or recommendations.

Instead, I would seek out people who truly know the engine in question and learn from them. Which is what we did in the case of the Ford Dorset/FL120. What I have been writing about the FL120 is simply parroting what we've been told by people with an intimate knowledge of these engines, particularly people we've become acquainted with in the UK.

This is the only diesel used in marine service we have done this for as it's the engine in our boat. I have no clue about the good, bad, or indifferent qualities of any other type of marine diesel.

Marin,
I know from my ships two machines; Mercedes Benz OM 314 in my Sailyacht and now in my Trawler 2X Ford Lehmann. Both "old" engine models. These engines keep in good service for 100 years. "Modern" Light Truck engines are no longer being built today in the same quality never , never more.
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Old 09-01-2014, 03:31 PM   #14
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Marin it matters not how old an engine is. It will be able to do what it did when new if it's in good condition. What are you talking about? Do the cylinders become weak w age and warp? Do the valves bend w age? Nonsense!

But you're right. A 1960 Ford truck engine should not be able to match the abilities of a 2014 Cummins.

Engines aren't like old cows or people that get weaker as the years go by. And if there's something wrong w them just fix it and it will be able to run like new.
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Old 09-01-2014, 03:39 PM   #15
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Except for emergencies there are three reasons to run pleasure rated engines at WOT for a minute or so. Test engine, hull and running gear, test the cooling system, spend money and be stupid.

How may would be happy to have their car tested at wot for 15 minutes? what would it prove?
Wifey B: I'd love to drive my car at high speed sometime. Maybe like the Bonneville Flats. Heck, I've never done more than half it's max.

But now some of us do like speed. Partly where we come from. Come from sailboats, you're not so speed picky. But we came from 55 knots on the lake, cruising at 40. While I was at the helm this morning I only opened up for 3 minutes. Then back to 1500 rpm or so, but ran at every speed from slow poke to what you call "stupid."

But on a trawler main reasons would be test. I mean that's how we use to realize it was tune up time. Once was fishing net around port prop. No vibration or anything but couldn't turn max rpm so took it in and fixed (by removing net but we didn't know that yet) before more problems
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Old 09-01-2014, 03:48 PM   #16
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Marin,
"Modern" Light Truck engines are no longer being built today in the same quality never , never more.
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Every decade since I have been able to talk the same has been said. I went to an antique boat show yesterday. I sure heard raves about the Hercules flat head 6, 6-71s and 283s. A friend there had a 80 year old vessel with 60 year old Gardiner. The tech's trip from England was not cheap to get it up to snuff.

I love the new stuff. Boats, cars, inverters, radar, plotters, G5s, HD TVs, IPad or whatever- just can't afford it all. My best gas truck engine yet is the newer GM Vortec. My BIL has the new big Mercedes delivery Van, he says the same about his modern diesel and he comes from the auto build business. Got passed by a Tesla yesterday, sigh.
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Old 09-01-2014, 04:03 PM   #17
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How may would be happy to have their car tested at wot for 15 minutes? what would it prove?
There you go right there. I have a guy at my marina who insists on running up his rpm's to "clean things out." He'll listen to my engines and if they don't purr like a kitten he'll scold me that I need to run them up, make 'em roar. Last season he went out and blew his transmission which took his boat out of action for half the season. My boat is an old thing and yes, I baby the engines, but just as Bayview says, old or brand new, we would never run our cars into the red zone on the tachometer, I don't get why so many boaters think it's such a great idea to push every component to the edge of the engineered tolerances.
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Old 09-01-2014, 04:08 PM   #18
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Here's what that looks like...compliments of chc!

Al, that looks like a speedboat's trail. The Coot's resembles a cruise ship's.





Planing vs. displacement speeds.
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Old 09-01-2014, 04:25 PM   #19
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I don't get why so many boaters think it's such a great idea to push every component to the edge of the engineered tolerances.
As the old adage goes, the truth is often in the middle. Let's be honest, most of us are extremely and way too anal about everything on our boats and we do baby our engines far more than they should be--the commercial guys must laugh at us. We are not dealing with a mass produced car and cheaply produced engines but rather ruggedly engineered marine diesels. I've seen more damage to boats because of lack of use and owners with good intentions. Again, we need to apply some common sense here.
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Old 09-01-2014, 05:05 PM   #20
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Marin it matters not how old an engine is. It will be able to do what it did when new if it's in good condition.
That's right. And the Ford Dorset was a weak, unreliable engine when run hard when it was new. That's why Ford gave up on it as a truck engine within a few years after it was introduced. I'm not talking about an engine getting weak with age, Eric. I'm talking about an engine being weak at birth.
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