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Old 02-22-2016, 09:35 PM   #1
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How long is it safe to run Wide Open Throttle?

I have twin Yanmar 110 hp 4jhj4lte motors. Rated max RPM is 3200 and that's what it will make. Someone ran my boat for 90 minutes at WOT yesterday. Is that a dangerous thing to do? My instinct was certainly not to like learning they did that.


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Old 02-22-2016, 09:43 PM   #2
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If engines are healthy, it will do no harm. If engines are weak in any way, that is when you will find the weakness!!

If you are going to charter the boat, consider turning down the throttle stop screws so even if "on the pins", the throttle will not be full.
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Old 02-22-2016, 09:43 PM   #3
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If you can dig up the spec sheet for the engine it should tell you. I don't think 90min is a big deal, even for the most moderately rated engines. Each manufacturer calls it different things, but Deere rates them M1, M2, M3 etc. Ours is M2 which means 16/24hrs at WOT, and the remaining 8/24hr at either 100 or 200 RPM below rated max RPM. M1 is continuous duty, WOT.
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Old 02-22-2016, 09:44 PM   #4
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You can run a diesel engine wide open under load for ever and not hurt it. Every diesel engine has a governor which limits the maximum RPM to the safe level determined by the engine manufacturor. The second worst thing you can do to a diesel is lug it around at low rpm and light loads. The worst thing you can do is use it for short periods of time and never give it a chance to properly warm up before shutting it down.
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Old 02-22-2016, 09:54 PM   #5
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How long is it safe to run Wide Open Throttle?

Thanks, everyone. I appreciate it!


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Old 02-22-2016, 09:57 PM   #6
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Diesel engines vary on the length of time it's prudent to operate at maximum capacity. Check with the diesel engine's maker regarding your particular engine.
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Old 02-22-2016, 10:20 PM   #7
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David,
If you are located in Cape Coral, I would call Mastry in St. Petersburg, they are the Florida Yanmar dealers. My guess is not to worry about it. You didn't mention if there were any issues - high temp, smoke, etc. If the engines can't handle WOT for 90 minutes, then I would be worried more about them being the proper engines.
Good luck
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Old 02-22-2016, 10:48 PM   #8
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My poor engine only sees two speeds, idle + 100 in no wake zones and WOT everywhere else. It hasn't complained yet.
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Old 02-22-2016, 11:22 PM   #9
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Quote:
Originally Posted by stanfromhell View Post
You can run a diesel engine wide open under load for ever and not hurt it. .
A term called duty cycle enters it. Also correct sized props to allow engine to comfortably reach rated RPM plus about 50 RPM. I'd not bless full throttle longer runs without knowing these two things.
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Old 02-23-2016, 12:15 AM   #10
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You can run a diesel engine wide open under load for ever and not hurt it. Every diesel engine has a governor which limits the maximum RPM to the safe level determined by the engine manufacturor.
This is untrue and a dangerous statement. Read Ski's reply above. The governor is a much more complicated mechanism than just limiting max RPM. And if your props are not pitched properly, you can do significant damage operating at WOT.

Most manufacturers publish a Max continuous power(MCP) rating. Cummins is usually 200rpm below WOT. And if I remember correctly, they do not recommend running WOT for more than an hour. Yanmar is similar. Will 90 minutes hurt it???? Ski's answer is the answer. Probably not... as long as all supporting systems are up to snuff.
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Old 02-23-2016, 12:31 AM   #11
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My question is why did you let someone else run your boat?
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Old 02-23-2016, 12:35 AM   #12
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My question is why did you let someone else run your boat?


Thinking the same like lending your chainsaw,trimmer,pressure washer ,wife.

They all come back rooted
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Old 02-23-2016, 12:45 AM   #13
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My question is why did you let someone else run your boat?
Charter, me-thinks.
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Old 02-23-2016, 02:34 AM   #14
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Just to reiterate as said above, there is no standard that is good for all diesel engines. I'd guess yours are rated for heavy duty, but I don't know. This is something you need to learn about your engines, their specific ratings and the manufacturers recommendations. We have some engines that are set up for fast vessels with low load factor and you run those a minimal amount of time at WOT, normally running at 80% load. On the other hand the same basic engine comes with medium and high load factor ratings and with a continuous use rating.

It's doubtful the 90 minutes did any damage, but none of us know what temperatures were reached or any other aspects of that run.
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Old 02-23-2016, 06:20 AM   #15
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While I agree that 90 minutes at wot did no harm, I do believe that extended operation at wot is bad.


That engine is 2 liters, so 110 hp is 55 hp per liter, not an insignificant amount of load, even for a diesel. Marine diesels fail much more frequently because one of the marine systems lets go and a severe overheat occurs with catastrophic results which is what Ski implied above. These events are the product of lack of maintenance and marine corrosion.


But assuming something like that doesn't happen, the more you load your engine the fewer hours it will last until significant blowby occurs, low compression makes it difficult to start, etc.


The following is mostly speculation, assuming no catastrophic event:


10 hp per liter, 20,000 hours
30 hp per liter, 10,000 hours
50 hp per liter, 5,000 hours
70 hp per liter, 2,000 hours


I base the above partially on the fact that the 370 hp Cummins 6BTA (63 hp per liter) was one of the few high performance recreational diesels to pass the Navy's 1,000 hour endurance test, much of which is at full load.


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Old 02-23-2016, 06:54 AM   #16
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How long is it safe to run Wide Open Throttle?

Quote:
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Charter, me-thinks.

Yes. It is under a three week charter right now. I only know it was run hard because I have a LandAirSea GPS tracker and it showed 14-15 knots from the Miserable Mile up to Tween Waters Marina on Captiva. I looked up the manual and it is approved for continuous output at 3110 RPM of its 3200 Max Rated Output, so it seems to be pretty good with extended high RPM as long as all the supporting systems remain working properly....


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Old 02-23-2016, 07:31 AM   #17
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I like the idea posed earlier since you are chartering the boat - turn down the throttle stop so it won't go over about 3000 rpm. Seems like cheap and effective insurance.
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Old 02-23-2016, 07:43 AM   #18
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I like the idea posed earlier since you are chartering the boat - turn down the throttle stop so it won't go over about 3000 rpm. Seems like cheap and effective insurance.

Yes. I would do this yesterday.

Why are they running so fast in the ICW anyway???
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Old 02-23-2016, 07:53 AM   #19
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EVEN Marine engines that are converted from industrial or heavy duty truck engines will come with 4 ratings.

From light duty to 24/&

ONLY the 24/7 rating can be held for "ever" the rest have duty cycle RPM and time limits.

IF there is no set of graphs for the engine you have I would take a look at real marine engines and reduce the power available to the charter party.

A simple rule of thumb is 80% max power at 90% rated RPM.for industrial diesels.

You may need to swop props to limit the un knowledgible renters abuse..
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Old 02-23-2016, 08:18 AM   #20
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You may need to swop props to limit the un knowledgible renters abuse..

I think I'll try the throttle stop at 3000 and consider dumbing down the props as last resort. Thanks again everyone. And yes I suppose the guy was going 15 in the ICW just because he could. LOL. And there are many boats going much fatter than that there, trust me.



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