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.

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.

eyschulman said:

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. .

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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.

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.

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.

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.

"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.

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.

Capt.Bill11 said:

"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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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.

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
_____________
Norbert

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?

CPseudonym said:

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.

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Here's what that looks like...compliments of chc!

Marin said:

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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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.
___________
Norbert

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.

bayview said:

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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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

supertramp said:

Marin,
"Modern" Light Truck engines are no longer being built today in the same quality never , never more.
___________
Norbert

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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.

bayview said:

How may would be happy to have their car tested at wot for 15 minutes? what would it prove?

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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.

FlyWright said:

Here's what that looks like...compliments of chc!

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





Planing vs. displacement speeds.

kthoennes said:

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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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.

manyboats said:

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.

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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.

Industrial engines or car engines, big difference

Industrial engines are rated and designed to run at their rated work load 24/7. They are capable of running at full rpm because that is usually very conservative. Most diesel engines run at less than 3300 rpm. One of the major factors in engine wear is the distance pistons travel per minute. Long stroke engines need to run at lower rpm to reduce piston and ring wear. Gas engines usually have shorter stroke engines and are capable of higher piston speeds. Marine engines based on car blocks that are run at 3500 rpm and up continuously, wear out much faster as a result. Car engines are not designed to run at full throttle for extended periods. If you pay attention to the tack in your car, your car engine runs at less than half speed most of the time.
Old engines suffer from metal fatigue, block distortion, valves stretch, broken valve springs , rod stretch, pistons wear and increased piston slap, rings break, or get gummed up. It's probably not smart to expect a old engine, no matter how well built to stand up to the abuse that a new engine is capable of. If you run your thirty year old engine at full speed you are pushing your luck. Thirty or forty year old designs may have some advantage in simplicity, but they are nowhere nearly as well machined or have the metallurgy used in modern engines. I'm old enough to have been buying and wearing out those old engines when they were new. I was thrashing my first Detroit in 1960, Car engines were worn out at less than 100K back then. Tune ups every 15k, oil changes every 1000, 1500 miles, tires every 15k , 20k if you were over 60. Today I would be horribly disappointed if my gas car engine didn't run 300k or more. I have very little nostalgia towards those old engines. If I had the money those old Detroit's in my boat would be modern JD's. Then I could hammer them wide open. I run my Detroit's at less than 1800 rpm, they are rated to 2800 rpm. They are 38 years old and still start every day and give another days labor. I almost never run them wide open, just occasionally to check them out, but seldom over 5 minutes. Still working after 38 years.

By the way:
What engines from the light truck series now used liner? FL has liner in 5 !!! different sizes.
I am German and I dont know in Europe no one middle class engine with liner .... Why not?
_____________
Norbert

...diesels are not "throttled".

The Ford diesels (our Lehmans) had a long and happy life as combine and generator engines, I think they even ended up in tractors, but Marin is correct, they sucked in trucks.

Check your "rating." My engine is rated "continuous" which means BTTW for 24 hours. My redline is 2100 rpm. My friend's Cummins, rated "recreational" is good for WOT for 1 hour, but he has almost double the HP and his engine redlines at 2800.

Scary that was an excellent post.

An old engine that's been over used for years and not taken care of or rebuilt when it's time can't be expected to haul the mail like it did when new. Taking care of anything that wears over time is "the cost of doing business". So even though I disagree w you to some degree I'm sure you're basically right. You obviously know more about it than me but I can't buy into needing to make big adjustments to how hard you run an older engine that's been maintained properly.

And some engines are just better than others .. Not thinking of the Lehman when I say that. I remember the Chrysler cars about 1950 had soft cylinders and so so rings. Cranks and inserts not very good either. Other brands of the time were clearly a notch up.

I think Marin's over the top but not really by much. I think he actually runs his engines almost 50% and that's way more than many here.

But thanks for the great post. We need clarity and objectivity here on engines.

skidgear said:

...diesels are not "throttled".

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Good point. And I believe most modern gas engines don't have the RPM limits set. Our boat Diesel engines have a govenor that limits the top RPM. And once the throttle is set the RPM speed is maintained, even under varying loads. Top RPM is called "high idle" by Cat.


1983 Present 42 Sundeck
Twin Lehman 135's

Supertramp,
From what I hear engines are made w a "throwaway" mentality. Not being judgemental or critical but in today's economy and circumstances manufacturers probably think "why build an engine that will be outdated and undesirable before it's worn out"? Or the cost of new engines is (relatively) cheap.

manyboats said:

...

I think Marin's over the top but not really by much. I think he actually runs his engines almost 50% and that's way more than many here.

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Run the Coot's JD4045 at 43% (1.7 gph vs. max. 4 gph) to move at a knot below hull speed at least 80% of the time.

manyboats said:

Supertramp,
From what I hear engines are made w a "throwaway" mentality. Not being judgemental or critical but in today's economy and circumstances manufacturers probably think "why build an engine that will be outdated and undesirable before it's worn out"? Or the cost of new engines is (relatively) cheap.

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Eric you're right,
We currently live in a throwaway society.
I've been living 30 years in Venezuela and here defective equipment be repaired.
Ford offers in its catalog 5 sizes for overhaul on, I think it's great
_____________
Norbert

Thanks supertramp,
Wish it wasn't so.

Mark thanks for the numbers I'll use them to relate to my own for better scope.
My max fuel burn is more of an educated guess so my percentage of load is a bit vague too. With your help maybe I can focus it more. Perhaps Mitsubishi can provide me w Max fuel burn?

In the not too distant future I want to go into Lake Washington and run alongside the floating bridge where they have a measured mile marked off. I'd like to see what my real speed is w/o any tidal effects. That may come under the heading of winter cruising.