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Old 08-14-2012, 10:45 AM   #1
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Wide Open Throttle

When was the last time you had your boat at WOT.

There are two WOT 's on a boat. There is the Maximum governed throttle on the engine. This is how fast the governor will allow the motor to operate and not damage the engine.

The other is based on things like prop, weight and how clean the bottom is.

The question is.

For how long and how often should you operate the engine at WOT.

SD
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Old 08-14-2012, 11:11 AM   #2
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Originally Posted by skipperdude View Post
When was the last time you had your boat at WOT.

There are two WOT 's on a boat. There is the Maximum governed throttle on the engine. This is how fast the governor will allow the motor to operate and not damage the engine.

The other is based on things like prop, weight and how clean the bottom is.

The question is.

For how long and how often should you operate the engine at WOT.

SD
Dude the governed no load top rpm is called high idle. The boat should be propped for the engine to turn the recommended top loaded rpm. The manual for the engine should tell what percentage of the time that it can run at top rpm.
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Old 08-14-2012, 11:16 AM   #3
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The last time I ran at WOT was 12 years ago when we first bought the boat and wanted to set up a speed table. The thought of running at WOT with the pistons fighting for position and no availible replacement parts (Volvo) gives me the willies.
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Old 08-14-2012, 11:34 AM   #4
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Dude the governed no load top rpm is called high idle. The boat should be propped for the engine to turn the recommended top loaded rpm. The manual for the engine should tell what percentage of the time that it can run at top rpm.
Not sure I follow you Don.

I have a low idle of 5500 and a high of 7500.

At WOT how could this be considered Idle?

With my boat I can achieve max RPM only in neutral.

Max is 2800 Underway is about 2550.

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Old 08-14-2012, 11:34 AM   #5
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For how long and how often should you operate the engine at WOT?
How long is a piece of string?

The engine manufacturer assigns a load factor ratiing to the engine and it states those limitations.

There is normally a "maximum continuous power" number in the specifications. If you want to know why, there are lots of academic studies available that go into great detail on what wears how much and why under different loading conditions.
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Old 08-14-2012, 11:48 AM   #6
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How long is a piece of string?

The engine manufacturer assigns a load factor ratiing to the engine and it states those limitations.

There is normally a "maximum continuous power" number in the specifications. If you want to know why, there are lots of academic studies available that go into great detail on what wears how much and why under different loading conditions.
A piece of string is twice as long as half it's length.

I have heard you should run a diesel up to WOT every so often just to blow it out. Blow out the carbon built up.

Is this bad advice?

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Old 08-14-2012, 11:54 AM   #7
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It all depends on how many engines you have and what type of anchor and rode are used.
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Old 08-14-2012, 11:58 AM   #8
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??
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Old 08-14-2012, 11:59 AM   #9
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I have a low idle of 5500 and a high of 7500.
Out of gear and throttle at idle your engine turns 5500 rpm? Wow.

It turns 7500 rpm tops? Wow again ... that is some CAT!

High idle means the rpm limit on the governor with no load. It is idle because there is no load. If it had a load it would not be at idle.
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Old 08-14-2012, 12:02 PM   #10
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I run mine up to WOT (under load) a couple of times each season. I usually keep it there for (about) 2 minutes or so. I watch for exhaust smoke, steam, and monitor coolant temp.
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Old 08-14-2012, 12:05 PM   #11
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Out of gear and throttle at idle your engine turns 5500 rpm? Wow.

It turns 7500 rpm tops? Wow again ... that is some CAT!

High idle means the rpm limit on the governor with no load. It is idle because there is no load. If it had a load it would not be at idle.
Sorry to many 000000000000's

550 idle

high idle would be 2800.

So idle does not mean sitting at the lowest RPM. Like right after start up. But refers to load?

So was Ancora right can it cause any real damage to run at WOT?

SD
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Old 08-14-2012, 01:31 PM   #12
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We have had our two FL120s to WOT (meaning throttles all the way up, transmissions in gear) exactly one time in the fourteen years we've owned the boat. (The engine surveyor did it, too, out of gear, but this was before we'd committed to buying the boat.)

We did it to get the WOT rpm for the prop shop that we were going to be getting new props from but who subsequently discovered our current props had been horribly set up prior to our purchasing the boat but were physically in fine condition and just needed a complete reworking.

The FL120 is rated at 120hp @ 2500 rpm. Whether that is their limited rpm, load or no load, or if they will turn faster at no load and full throttle is something I will never find out unless someone who already knows tells me. We don't take our engines higher than 1800 rpm and our normal cruise power is 1650 rpm.
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Old 08-14-2012, 01:37 PM   #13
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The FL120 is rated at 120hp @ 2500 rpm. Whether that is their limited rpm, load or no load, or if they will turn faster at no load and full throttle is something I will never find out unless someone who already knows tells me. We don't take our engines higher than 1800 rpm and our normal cruise power is 1650 rpm.[/QUOTE]



Do you think it could do some damage to the engines?

It seems no one knows for sure.

I talked to Cat the tec told me diesels are built to run at WOT. Such as use in a generator and on heavy equipment. They frequently run at WOT.

The question remains is it good or bad to run them up occasionally?


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Old 08-14-2012, 02:08 PM   #14
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High idle is usually several hundred rpm above power rated rpm. Probably around 2700 for the Ford Lehman.
I run my Mitsu at WOT in gear 5 or 10 times a year. It tells many things. Most importantly it tells if you're propped correctly. WOT should produce the rated rpm as in 2500 for the Lehman's. One should run WOT for 2 or 3 minutes to test the fuel system for it's ability to deliver fuel. With my old Perkins we boated around in the San Juan Is for awhile thinking our Perky ran just fine. In the Swininomish Channel I ran it at WOT for about 2 minutes and the engine abruptly quit. Never would have known if I hadn't gone WOT. Rpm hunting, smoking or other irregularities will tell how your engine is running and there's no better way to find out. Don't do it in bad place like I did though.
Marin what do you think is going to break or get damaged when you run WOT?
Or when you cruise at 2100 rpm?
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Old 08-14-2012, 02:34 PM   #15
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Running your engine to the pin in gear should be limited by whatever the engine manufacturer has written for that engines rating. (assuming to the pin is the rated RPM too). Like RickB posted. Whatever that number is...you should NEVER be afraid to get it to the pin and keep it there as long as the manufacturer says is OK. Especially the single engine guys...if you can't get there or stay there...then how do you really trust you engine for the long haul?

Running your engine to the pin without the engine in gear is a trouble shooting operation. While it shouldn't hurt your engine to get it there and check a few things..I wouldn't be comfortable with it up there for more than a minute or two...but that's me and no mechanical/scientific reason to back it up...but then again ...why would it ever be there for more than a very brief time?
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Old 08-14-2012, 02:51 PM   #16
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Marin what do you think is going to break or get damaged when you run WOT?
Or when you cruise at 2100 rpm?
I know what is going to have its life shortened if an FL120 is run at full throttle or power settings much over 2000 rpm for longer periods of time because a fellow who got real rich in the UK overhauling them told me.

The injection pump.

According to him it is the single weakest link on the engine and is one reason the Dorset engine proved to be such a miserable failure as a truck engine. Other components of the engine are less-than-ideal, too, but the pump was--- under high rpm, constantly changing high-ish loads which is what you have in an over-the-road truck--- very prone to either outright failure or rapidly deteriorating performance. Our acquaintance told me that overhauling the Minemec/Simms/Cav in-line pump on the Dorset engine back in the day let him pay cash for a new Rolls Royce.

Ironically that same pump did just fine under lighter and more constant loads which is why the Dorset engine proved very good in its day as an industrial and agricultural engine. And as a marinized engine in boats.

The Dorset engine is also very susceptible to heat damage. In fact, our friend said overheating is the number one killer of the Dorset engine. Not that it is prone to overheating but if something happens with the cooling system and the engine is not shut down before an overheat occurs Bad Things happen fast. The head gasket is apparently looking for any excuse to blow and the head itself will warp quite happily.

We met this fellow initially in Ganges on Saltspring Island where he was cruising in his sailboat which had---- an FL120 in it. He asked us what kind of engines we had and that's what got the conversation going. He had not only owned one of the biggest Ford of England diesel repair and overhaul shops in England but he said that for many years he'd been a consultant to Ford of England on their diesel engine programs. The voice of real-world operations, as he phrased it.

The Dorset, he said, was not a bad engine given the era in which it was designed. But it was designed at a time when trucks were rapidly getting larger and heavier and road speeds were going up. The engine would have been great in the 1940s. But it simply wasn't up to the job that was being asked of it.

In a boat, he said, it's a great engine. But only if you run them under the loads and rpm at which it experiences it's longest, most reliable life. The best rpm band, he said, is 1500-1800. And never, ever, EVER, he cautioned me several times, let them overheat. If I think one might be, he said, shut it down as soon as you think that. Don't wait to see if the problem is really happening, or will get worse. Because if it does get worse by the time you realize it the damage can already have been done.

Now I've heard much of this from other sources in the marine diesel industry over the years, and I'd read about the Dorset's failure as a truck engine before I met this guy. But he'd built a business on dealing with this and many other Ford of England (and Perkins, etc.) diesels. So I give him a lot of credibility.

In my book, reality and first hand experience trump theory every time. So while someone like Steve D'Antonio may arise from his armchair and preach about 75 percent power loads all the time, every time or whatever, I'm going to listen to the British guy who bought a Rolls Royce for cash on the money he made fixing, overhauling, and living with the kind of engines that are in our boat.
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Old 08-14-2012, 04:05 PM   #17
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Thanks Marin. That is one for sure.

So anyone with an FL120 should follow your advice.

It seems that it is going to be an as per engine.

The Cat dealer is of a mind that it is a good thing to do once in a while.

Any others?

SD
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Old 08-14-2012, 04:13 PM   #18
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We have the Ford Lehman SP135. WOT is 2500 rpm's. We run WOT 4 or 5 times a year just to see if everything is OK, ie; temps, fuel delivery system, cooling, prop, etc.
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Old 08-14-2012, 04:29 PM   #19
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Thanks Marin. That is one for sure.

So anyone with an FL120 should follow your advice.

SD
Anyone with an FL120 can do whatever they want to do. If they want to operate differently I'm not going to tell them they're wrong. I'm just not going to do what they do. What I've related is what we do and why we do it.

I've read things on other forums from people who've said they run their FL120s at a constant 2200 rpm and change their engine and injection pump oil every 500 hours and they've never had a problem in x-hours or years.

All I can say to that is that every engine will run without a problem until it has one. We're interested in maximizing the time between now and "until," so we act on the advice and experience of people we've met in the engine business who we feel are very credible when it comes to this particular engine.

Other people should act on whatever they believe in.
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Old 08-14-2012, 05:01 PM   #20
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Like the guy said. It's a great boat. The engine was running when it quit.

We can't all get the advice that you have received.

It sounds credible to me.
All we can do is get the best advice we can and act on it.

Or react as the case may be.

Sd
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