Do you run at WOT for extended periods of time?

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Rick James

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So I've got a 1977 Johnson 15hp motor on my Sears 12' semi-v. I've got a handful of fishing spots that really require a pretty good distance run to get to my fishing destination. Sometimes I'll run the boat 5-10 miles at wide open throttle.

My main fishing partner has said to me that with the ethanol on today's gasoline, that motors run hotter at WOT, and my motor is much more likely to let loose if I run it this way for extended periods of time.

Your thoughts? Any validity to this claim?
 
The only reason I don't run WOT is to conserve fuel. If I back down on the RPMs to around 4000-4500 I use much less fuel. As for the reasons your partner states...I have no idea. Never heard of that...but interested if someone else has.
 
I don't run WOT as I do not want to waste fuel either. Plus I still have some room to accelerate if needed. But I have not heard about the Ethanol causing excessive heat buildup.
 
Ethanol will make your motor run cooler not hotter.(not anything noticeable though)

Running wide open does not hurt your motor as long as you haven't tweaked the timing to make it run higher rpm's than factory.
 
WOT for me is about 5500 rpms and my motor drinks gas at that rpm. I back off to about 4000-4500 and I get lots better fuel mileage.

As far as the overheating thing, never heard it before.
 
Thanks for the info guys, much appreciated. I'm not super concerned now hearing some of the input, and gas mileage isn't really a concern either.......even at WOT I'm getting somewhere around 20+ miles per 3 gallon tank with my little 15hp motor.
 
Running at wide open throttle will not hurt after 5-10 miles if it held up after the first mile. After running and heating up initially the temp should stabilize at a point and stay there if nothing is wrong or nothing drastic changes. That is saying you are running at factory specs and not trying to turn it faster than specs. It should be able to run until the tank is dry same as your car.
 
It shouldn't be an issue as long as you are propped correctly and not over-reving or lugging the engine. ie within the recommended wot rpms. Make sure you are not running hotter than stock plugs, too. I have found that in many a small outboard where a previous owner was compensating for slow speed fouling. Keep in mind, that most small outboards have little or no gauges so knowing the sound, performance, etc, is your only early warning system.
 
For those who run extended WOT I would definitely run a little extra oil. If you look at any of the older Owners manuals they almost all clearly state that for extended WOT running or racing (Which is extended WOT running) that 24:1 mixture is recommended. Although most will not go that far with the ratio it never hurts to have a little extra lubrication protection.
 
IVE NOTICED MY 80' 25HP JOHNSON IDLES KINDA SH@%%Y WHEN TROLLING OR IDLING ALONG, ONLY WITH 92 OCTANE OR HIGHER. WITH 89 IT PURRS LIKE A KITTEN AND DONT MISS A BEAT. JUST MHO....
 
Rick James said:
So I've got a 1977 Johnson 15hp motor on my Sears 12' semi-v. I've got a handful of fishing spots that really require a pretty good distance run to get to my fishing destination. Sometimes I'll run the boat 5-10 miles at wide open throttle.

My main fishing partner has said to me that with the ethanol on today's gasoline, that motors run hotter at WOT, and my motor is much more likely to let loose if I run it this way for extended periods of time.

Your thoughts? Any validity to this claim?

Given reasonable wot speed, you are talking 15 minute to half hour runs, not really that extreme.

I haven't heard that it raises temp, but allot of reports that when water stratifies out, or crap that it dislodges can cause lean conditions in the carb. If this happens it will run hot and can damage your engine (pre-ignition or detenation).
 

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