WOT - why?

[Zachary]

I routinely hear recreational fisherman discuss a particular boat's speed at WOT. In listening to such discussions, I am perplexed as to why people, especially recreational fisherman make such a big deal about WOT. I understand that there are go-fast boats that are akin to sports cars and I understand that purpose for driving fast at WOT, but why on fishing-type boats?

For me, on 4 stroke outboard motors, I look at speed and economy at 4,000 rpm, not WOT at 6,000 rpm because most of cruising is done around 4,000 rpm. I myself have driven a boat at WOT, but that was just for a couple of seconds just to see what the top speed was, and even then it was after the engine was properly broken in.

My questions are as follows:

1. How often do you guys run your engine at WOT?
2. For how many seconds/minutes do you guys run your engines at WOT?
3. Any mechanical problems with your engines?

Thanks in advance for your input,
Zachary

 

[MolarBoater]

Testocerone. Purely testocerone. Sometimes Viagra, but I'm not there yet as my engine is well maintained.

OK seriuosly, I run WOT everytime I get on plane then drop it down to @3400. No mechanical proplems. Even when trying to out run thunderstorms and lightning I always back off just a little. Running at WOT consistantly is just tempting "fate".

Now if we have the same boat and you run a 115 WOT and I run my 140 at 85% for the same mph, guess who's motor will get better gph, run cooler and last longer?

 

[Cape Codder]

Cape Codder

Although My Engine Is Still In The Breakin Period I Open The Engine Up For A Few Seconds And Then Cruise At Various Speeds. I Would Never Run Any Internal Combustion Engine At 6000 Rpm, For Any Lenght Of Time. Im Sure Any Damage Would Show Up After The Warranty Period Ends.

 

[Dave LeGear]

There are several reasons why this is done...
1. To make sure your prop is of the proper pitch and size for the recommended WOT range of the engine and your hull.
2. To help clean up the engine of deposits.
3. On 4 stroke engines it is needed (critical) to "burn off" all the moisture build up in in the oil and oil sump. If such moisture is left behind as the engine cools AND you do not have the correct type of Marine 4 stroke oil (and that is only a band aid). Then you could have rust starting to form inside the block and crankcase. It is very important that the oil get "above" 180 degrees to do this, and that is very hard to do with any 4 stroke outboard when running and remember, that with each intake stroke, you sucking in that much more moisture that needs to go away.

So you have to remember that unlike your truck, your outboard engine is setting in water (or worse yet salt water) and that needs to be removed from the oil. So I run mine flat out (after 5 min warm up period) for several minuets or parts of my run on each trip to make sure I only have "oil" left in my oil sump, and not a foaming mixture of water and oil that could starve the engine of the one thing that keeps it all glued together, pure oil AKA Motion Lotion

Hope this helps?
Dave

 

[Zachary]

Very good and detailed response. I do have a few questions.

With regards to burning off any deposits, I can understand this with regards to cars because they tend to cruise at, say, 2000 rpm on the highway. I have gunned my cars every so often in order to remove any deposits, and notice that the engine runs better afterwards (although this is not scientific, just my perception). On the other hand, when outboard motors - whether 2 stroke or 4 stroke - cruise around at 4,000 rpm, then that should be way more than enough rpms to burn any deposits. Am I wrong?

With regards to water/humidity in the oil, I understand that revving the engine to WOT helps heat up the oil and thus burn any humity/water. However, wouldn't it be just better to change the oil during shorter intervals?

With regards to making sure than a propeller is the right size/pitch, I also understand that point as well. However, shouldn't the dealer, who sells that brand of boat, with that brand of engine, and thus that size/pitch of propeller, know the proper size/pitch so that you don't need to push your new boat at WOT? Honda and Yamaha, for example, have detailed performance figures for many types of props on the same boats. That way you know exactly what the figures will be with particular props.

Am I wrong on any of these issues?

Thanks,
Zachary

 

[Cape Codder]

Cape Codder

At My Age Almost 60 I Have A Real Hard Time Getting My Mind Around The Idea Of A Small Round Object Usually No More Than 12 Inches In Diameter Pushing 1000 Lbs Or More Thru The Water At 30 Plus Mph For Miles And Miles All At About 6000rpms. I Know It Works For Some Here In South Florida As Ive Seen Them Do It. Thanks To All The Well Meaning People On This Site.

 

[fridaysoff]

The number "ONE" reason, at least in my case is every once in a while you just have a "NEED FOR SPEED"!!! Actually I usually run my motor at WOT just before I get back to the boat ramp. I do this to make sure that it will reach WOT and when I take it back on the water it should run properly based on it's performance when I put it up.
JD

 

[Dave LeGear]

Very good and detailed response. I do have a few questions.

With regards to burning off any deposits, I can understand this with regards to cars because they tend to cruise at, say, 2000 rpm on the highway. I have gunned my cars every so often in order to remove any deposits, and notice that the engine runs better afterwards (although this is not scientific, just my perception). On the other hand, when outboard motors - whether 2 stroke or 4 stroke - cruise around at 4,000 rpm, then that should be way more than enough rpms to burn any deposits. Am I wrong?

With regards to water/humidity in the oil, I understand that revving the engine to WOT helps heat up the oil and thus burn any humity/water. However, wouldn't it be just better to change the oil during shorter intervals?

With regards to making sure than a propeller is the right size/pitch, I also understand that point as well. However, shouldn't the dealer, who sells that brand of boat, with that brand of engine, and thus that size/pitch of propeller, know the proper size/pitch so that you don't need to push your new boat at WOT? Honda and Yamaha, for example, have detailed performance figures for many types of props on the same boats. That way you know exactly what the figures will be with particular props.

Am I wrong on any of these issues?

Thanks,
Zachary

Carbon Deposits mostly form during the engine cool down (burning away) process (like leaving eggs on the skillet too long) and without the correct fuel additives that problem can get very bad and force you to use a higher than normal octane rating fuel due to all the build up (be it your Truck or Outboard). Now many cleaners will remove gum and varnish, carbon though is hard, yet very porous (like a sponge) and very hard to remove. High Speed runs help to remove such deposits as long as you use the correct cleaner like Techron or Yamaha's ring free (which is the same stuff) yet the problem effects 2 and 4 strokes differently.

2 Strokes (mostly older ones) leave a ton of deposits behind due to the burning of oil on every power stroke. If one uses a high quality (synthetic) 2 stroke oil the issue is greatly reduced, but it is still issue for most engines even the newer HDPI models. Over time the rings on the piston's can seize up and the loss of HEAT transfer from the piston to the block for cooling, causes the most failures. And here you thought that rings were only for oil control and compression sealing


4 Strokes suffer carbon build up mostly on the piston crowns and valves slowly forcing the owners to use a higher and higher octane grade of fuel to get the same performance. The carbon deposits on the valves and injectors is a real killer of performance and picture your engine (in human terms) trying to jog with your hand over your mouth... So with the correct fuel additives and higher temps from such runs, you can help knock off these deposits. Now as far as crankcase oil goes, the left over moisture that does not get burned off (really is it boiled off due to the heat) forms a acid that causes the rust that "can" lead to failure. So the thinking that changing the oil more frequent is logical, though does not help if you do not get the engine temps up "High Enough" to "remove" the water and the acid that it forms afterwards in the first place... This no matter how new or "Clean" the oil really is.

So yes the dealer "should" not only know which prop is best for your combo, your combo will change with "your" boat loading for most times, it is just the tech and maybe a few gallons of fuel in the boat for such testing and break in process (if they even do such) when it is on the dealer's lot.

We also have to remember that these engines are design to run at such RPM's for extended periods of time. Now I don't run flat out for miles upon miles upon miles, it is needed during each trip on the water for some amount of time to get rid of the moisture build up and it's possible very corrosive effects.


So like our 60 year old brother in the other comment (like my Father) who was raised (and I can remember some myself) in the era of Big Block, Big Piston, marginal lube qualities the "Thought" of running anything stock above 5 grand makes them shiver... Those old cars could come all unglued if one would to run them at such RPM's for very long. Today though it is a different ball game... We have much smaller engines with different cam shaft profiles, Computer controls, better metals, and better lubes and gaskets, returning the same amount of work and at much better fuel burn rates... Granted, you will not get your best MPG when running that fast (like 4000 to 4500 RPM will) it still does not hurt them at all to run them that fast for 5 to 15 min on the run back to the ramp and can hurt them in the long run, if you do not


Now I do not subscribe to this "Drive it like you Stole it" theory, that does come into play some when it is under warranty cause that is the time you WANT it to come unglued IF it is going to happen to your engine... Engine's can fail at any time I agree, but I would much rather have that failure (after recommend break-in runs) while the factory will cover those repairs and not years later for sure...


Hope this helps answer your questions some? And some of the guys here might say "What does that mouse driver Dave know?" (Fair question) Well many may not know this, but I was first an Engineer in the Coast Guard, Chief Engineer for a private SAR & Salvage firm, then spent 10 years as an Import German and Japan (Porsche, Audi, BMW, Toyota) Automotive Service Director... So you could say, that Dave "may" remember which wrench to grab and when, (though not as good as I did 10 years ago) and did that for quite some time before trading in the 10mm box end for a mouse full time. At lest now the keyboard and mouse don't have grease all over them all the time like they did years ago! Ha-Ha...


Dave

 

[Cape Codder]

cape codder

hi dave-thanks for the technical info on the running of 2 and 4 stroke engines. very clear and concise. however, im almost 60 not 60 yet. big difference! im told at 60 ill spend more time on web md than triumphowners. bill

 

[Zachary]

Dave,

Thanks for the very informative email - I really appreciate it. I guess that I agree with you on many points, one of which concerns driving at higher rpms before the warranty expires, but after the break in period.

Zachary

 

[Codfish]

I just wish us west coasters had optimum ocean conditions more often so we could run WOT. If I get much above 3,500 the boat wants to fly off the lips.

I run WOT in the bay though. Usually on the way in, to do all those things already discussed so eloquently by Putershark.

Great explanation Dave.

codfish

 

[Fischer53]

Codfish
I would trade WOT for the halibut in your avitar.