Operation at WOT

[tomasz]

For how long I can operate my engine at WOT? I want to know so I don't abuse it.

 

[thumpar]

Re: Operation at WOT

Until it blows up.

But really WOT won't hurt unless that is how you drive it all the time. Back off a few hundred RPM when you really need the power and cruise 1k-1.5k RPM below WOT.

 

[HT32BSX115]

Re: Operation at WOT

For how long I can operate my engine at WOT? I want to know so I don't abuse it.

Howdy,


You're going to get answers all over the map!

But you can essentially run at WOT until the engine fails or it wears out. (understand that if you run at WOT, you wear it out MUCH quicker)



Yes, I know that was a smart-azz answer.

If you do not have an operators manual, here's what Mercruiser says:

After Break-In Period
To help extend the life of your MerCruiser power package, the following
recommendations should be considered;
? Use a propeller that allows the engine to operate at or near the top
of the maximum RPM range (See ?Specifications? section) when
at full throttle with a normal boat load.
? Operation at 3/4 throttle setting or lower is recommended. Refrain
from prolonged operation at maximum (full throttle) RPM

Regards,


Rick

 

[wca_tim]

Re: Operation at WOT

it'll also use a whole heck of a lot less fuel at 3/4 throttle than wfo...

the trick is to figure out how fast you want to go much of the time, and put enough engine in it that you can go 1 1/2 - 2 times that fast a wot.

 

[tpenfield]

Re: Operation at WOT

43.2 seconds . . . but it is just a guess.

It is good to run the boat up to WOT once in a while for short durations as you can see if it is performing according to its 'specs' and to see if anything has changed from the last time.

It is hard to say what will 'abuse' the engine as there are all sorts of variables that come into play. Just keep in mind that the 'go-fast' crowd changes out their engines on a fairly regular basis.

 

[paultjohnson]

Re: Operation at WOT

IMHO... there is only so many... horsepower-hours/ revolutions in any engine, the faster you use em up, the sooner there gone

 

[tomasz]

Re: Operation at WOT

Thank you all,
Those are some good responses to my question. And trust me I will remember all the advise as I want my engine to last long long time

 

[HT32BSX115]

Re: Operation at WOT

Thank you all,
Those are some good responses to my question. And trust me I will remember all the advise as I want my engine to last long long time

My last boat, (Dad bought it new) was a 1966 Mark Twain with 150 Mercruiser engine (230 cu-in 6)

We ran it mainly at approx 3/4 throttle or more all it's life with an occasional (brief) full throttle run each time out on the lake, some times multiple times in a day..

I sold it in 2005 (39 years for the math challenged) and we never had the head off the engine.

WOT once in a while will hurt nothing. Just don't run it at WOT all the time or you may wear it out a quicker. How much quicker? Maybe my old 66 might have only lasted 20 years

Let me also add that most of these engines are not built to make the MOST power possible. They're sort of like aircraft engines in that they're designed to make a fair amount of power on a continuous basis.

Running them (continuously) at no more than 80% (of max) power gives the most longevity.

Aircraft engines are similar in that they're slow turning (typically 2500-3000 RPM) , high cu-in displacement and designed to run continuously at fixed power settings (usually 75-80%) but some are designed to operate at 100% power continuously. (I have an engine rated at 180 hp 2800 RPM continuous It has a 2000hr recommended time between overhauls)

Use your own best judgement!


Cheers,


Rick

 

[theBrownskull]

Re: Operation at WOT

I would think running it WOT for a couple of minutes is ok but it depends upon the engine and how it is set up. I remember reading somewhere, can't find it now, that 5 minutes was the max.

 

[wca_tim]

Re: Operation at WOT

Note that one thing you can do to help is to install a large oil cooler with a thermostat. a lot of the problem with running at higher rpms for a fairly long period of time is that the oil gets hot and thin in the mains... I proved this very clearly on my current engine by temporarily putting one of my temp sensors in the port above the oil filter port. it is also obvious without the oil cooler in place because after even a short hard run the oil pressure at lower rpms drops a lot (I take the oil pressure off the port in the front of the block, which lets you see how much pressure you're losing. I see the same sort of thing on my car btw...

Finally, it depends on how an engine is set up. if you build it to hold up and keep the oil cool... I have probably run as long as 30 minutes really close to wot...

 

[tomasz]

Re: Operation at WOT

My last boat, (Dad bought it new) was a 1966 Mark Twain with 150 Mercruiser engine (230 cu-in 6)

We ran it mainly at approx 3/4 throttle or more all it's life with an occasional (brief) full throttle run each time out on the lake, some times multiple times in a day..

I sold it in 2005 (39 years for the math challenged) and we never had the head off the engine.

WOT once in a while will hurt nothing. Just don't run it at WOT all the time or you may wear it out a quicker. How much quicker? Maybe my old 66 might have only lasted 20 years

Let me also add that most of these engines are not built to make the MOST power possible. They're sort of like aircraft engines in that they're designed to make a fair amount of power on a continuous basis.

Running them (continuously) at no more than 80% (of max) power gives the most longevity.

Aircraft engines are similar in that they're slow turning (typically 2500-3000 RPM) , high cu-in displacement and designed to run continuously at fixed power settings (usually 75-80%) but some are designed to operate at 100% power continuously. (I have an engine rated at 180 hp 2800 RPM continuous It has a 2000hr recommended time between overhauls)

Use your own best judgement!


Cheers,


Rick

Now, that is a quality explanation my friend. Thank you.

 

[airshot]

Re: Operation at WOT

If I may add my two cents here, I have a 1983 Starcraft Islander 22' with a 3.0 4cyl I/O. Motor is all original, uses a little oil but has a few drips under her. I have to keep oil absorber under the engine, however she runs excellent. Always been maintained properly, and put up for the winter correctly. She will do 34 mph at 4600 rpm but that is not my normal cruising speed. We typically run on lake erie so depending on wave conditions my normal operating speed is 2800 - 3400 rpm which puts me at just under 20 mph to about 25 mph. On ocassion I do open her up to wot to know that she still performs well and blow some carbon out of her. This lasts about 5 minutes then back to normal cruisin speed. You will see that normal is plenty fast enough to pull grandkids on a tube. Look at how long this motor has lasted and still runs great and strong so I am not saying my way is perfect but has certainly worked well for me.

Airshot

 

[mohead1]

Re: Operation at WOT

Dont forget the maintenance factors too.....if you run it hard, you need to increase the maint. on the engine and other parts including the outdrive. Higher frequency oil/gear lube changes, fuel filter/water separator changes, etc. to compensate for the hard running