How Long Is Too Long At WOT?

TyeeMan

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This is a question I've had in the back of my mind for years and casually looking have not found a good answer.

How long (time) is too long running out at WOT? You see folks with outboards, I had a few as well over the years, and you could run them for miles and miles at WOT with seemingly no problem.

The caveat is where I do all my boating here in Minnesota I wouldn't be able to run for much more than a couple minutes before running up on land unless I would visit lakes like Leech Lake or Millelacs which have some size to them. Even then you'd be limited to a fairly calm day.

I've had 3 I.O's over the past 13 years, first a 3.0L, then a 4.3L and now a 5.7, and it still seems strange to run basically a car/truck engine at WOT for minutes. And the 5.7 4bbl I have now gets pretty thirsty at WOT so I don't go there very often.

Anyway, there's probably not an exact answer, but like I say I've always kinda wondered.
 

tpenfield

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You are correct, no exact answer . . . but it seems that outboards are more tolerant of running at high RPM. I/O's maybe not so much. Often sea conditions dictate how fast you can run. The lake boating folks have greater opportunity to run at WOT.

If I were to advise on a 'safe' limit . . . I'd say 1-2 minutes max at a time.
 

mr 88

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This is a question I've had in the back of my mind for years and casually looking have not found a good answer.

People will equate the drag and weight of a boat ( more so a cruiser style boat than a go fast that you can trim out and may be running on a pad ) to pulling a trailer with load on it up a hill. That in itself won't harm.a engine,but it probably will cause premature wear and tear on the whole drive train.





How long (time) is too long running out at WOT? You see folks with outboards, I had a few as well over the years, and you could run them for miles and miles at WOT with seemingly no problem.

Untill recently most outboards for recreational use were on smaller, LIGHTER, boats so the drag of the hull wasn't killing the engine.

​​​​​​

The caveat is where I do all my boating here in Minnesota I wouldn't be able to run for much more than a couple minutes before running up on land.
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That's why you have a steering wheel. I bet if you turned it you would avoid land and could run WOT to your hearts desire.


And the 5.7 4bbl I have now gets pretty thirsty at WOT so I don't go there very often.

One good reason people are not running WOT when out joy riding.


Anyway, there's probably not an exact answer, but like I say I've always kinda wondered.

Hope I answered a few of your questions that you didn't answer yourself !
 

Scott Danforth

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Many times I have ran my 5.7 at WOT for about 5-10 minutes at a time. 13 miles of river between the boat launch and the inner coastal is a long time. WOT for the first 3 miles, then back it down for a no-wake area..... then back to WOT for about 9 miles, then back it down to about 3500 RPM
 

mr 88

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The offshore racers with high performance engines, [ built to go and probably blow ] run on the edge at WOT for quite some time. So in reality you could run for hours at WOT with no issue if your pocket is deep enough and your coolant system is working correctly.
 

dingbat

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Untill recently most outboards for recreational use were on smaller, LIGHTER, boats so the drag of the hull wasn't killing the engine !
Your geezing...”recently” was close to 50 years ago....lol.

Outboards have been pushing heavy saltwater boats for years

The first twin engine boat I ran was 1983 Grady Trophy with a pair of 175 Evinrudes hanging off the back.

The 1986 Grady Overnighter I bought new had a 200 Black Max bolted on the transom.
 

TyeeMan

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Hmm, interesting comments all. Maybe I'm over analyzing the whole thing.
 

Maclin

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If you have the engine "loaded" properly, i.e. gear ratio and propping, and cooling system is performing well, you can go 10 minutes or more, maybe all day. If you are under geared or under propped then maybe 2 minutes and "It might get loud".
 

harringtondav

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I have an '82 Merc 4 hp "Gnat". I ran it WOT for most of the time pushing the canoe up river, and it's fine. As said above, O/Bs, particularly 2 strokes seem very tolerant.

My theory on I/O and automotive engines is any engine will experience cylinder, ring, and main bearing wear after enough revolutions and piston up-down cycles. So an engine run at a constant 4800 rpm will wear out 60% sooner than an engine run at 3000 rpm. I rarely push my auto engines over 4K rpm, mostly at short on ramps. I occasionally run my 4.3 I/O at WOT to see if it's holding it's top speed, but only for a 1/2 minute.
 

H20Rat

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Any decent engine that isn't overloaded will happily run near its redline for a long time. There isn't anything magical that happens at higher RPM. My Yamaha 4 stroke snowmobiles will happily rev over 10k, and they will outlast almost any other snowmobile out there, most of which run at lower RPM. Also, my RV has a Ford 460 in it, and frequently runs at WOT for minutes at a time pushing a really heavy RV down the road. It has happily done that almost 40 years with no issues.
 

TyeeMan

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Ok, ya got me. :)

I will say this, my 5.7 is as smooth as silk and sounds really, really nice when she's running all out. With two people in the boat, drive nicely trimmed I have to pull back just a bit or I'll hit 5000 ripms. I'd say that's about right.
 

Scott06

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As you demonstrated you're prop'd right and watch over rev' ing. If you keep up with maintenance and have good oil pressure no issue to go WOT or close to it for extended periods of time. I've done it regularly for 20-30 minutes.

On my previous boat with a 3.0, when I'd take my kids tubing I'd be between 4000-5000 for an hour straight except when somebody fell off or to switch riders. That boat was 25 years old and had about 900 hard hours on it, but I always kept after maintenance - oil changes and make sure it doesn't get hot.

Of course running it harder will accelerate wear, but bottom line very durable if you take reasonable care of it and you can run at or close WOT for significant periods of time.
 

Redrig

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Crap , I thought you were supposed to run at WOT as often as possible.

I have ran mine for probably an hour straight in the low 4s .

I boat at a huge lake (Powell) and when we get glass I can make some good distance in one run . Of course keeping an eye on temp and listening for any changes. Looks like I will have to change that strategy and do some putting along the way.
 

Silvertip

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Well now -- how about NASCAR engines of 355 CI that run 500 miles at 7500 rpm and up with few interruptions. Yes - balanced to a gnats eyelash with cams, springs, exhaust and oiling systems for the application but you can run a common car/truck engine (properly geared and propped) at WOT without a problem. The camshafts in these engines just don't allow high rpm breathing so they self-limit (to a point). Yes -- life of the engine will be shorted but by how much is anyone's guess. Stuff breaks. The conditions under which that happens is also anyone's guess and can happen at any rpm from idle to 5000rpm. Your ears, wind in the face and screams from your passengers will be more of a limiting factor as to how long you should run WOT. Otherwise the rule is "until it breaks".
 

Scott Danforth

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to add to Silvertip comment.... more engines die of improper maintenance and neglect than they do when you run em like you stole em
 

dingbat

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Didn’t realize that running 2-3 hours (60-90 miles) offshore to go fishing for the day then back was such a big deal....lol
 

Lou C

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One the newer GM small blocks, the roller cams and lifters can take this more easily because there is much less wear on a roller cam than on a flat tappet cam. It also depends on the current condition of the engine you have. If its in good shape, good compression, oil pressure and cooling/exhaust system is functioning properly, then it should not be a risk to do this for a few minutes. If you have any doubt about the lube system, cooling/exhaust I would stick to 3/4 of redline ie about 3600 rpm.
The motor oil you use makes a difference too. You want an oil that will maintain its viscosity at elevated rpms for an extended time period. Not a 10W-anything. If I was going to do that regularly, I'd be using the Merc 25/40 or a syn 20/50.
Yes I know that NASCAR engines run low vis oil but their valve trains are completely different in materials from what is used on a stock GM marine engine.
 

racerone

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What would a Mercruiser owners manual say ?????----Is there a warning about running full throttle ?
 

Scott06

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Yeah it's say you may smile more at WOT... and where ever you buy your gas will smile more too...

i know not the answer you were looking for...
 
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