Outboard Motor Power Rating: Continuous Full Throttle

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Author Topic:   Outboard Motor Power Rating: Continuous Full Throttle

bmclernon posted 03-19-2006 11:18 AM ET (US)
I notice throughout all the performance literature Mercury establishes certain performance parameters for a specified RPM or power setting. My experience with SEL airplanes tells me after take-off you don't go blasting around WOT. Crusing or continuous power is usually much lower (50 - 75%).
Are modern outboards rated for continuous WOT operation? If no, what are specifications for Continuous power operation in modern outboards (2-stroke and 4 stroke). Example: Mercury mid-range OBs.
Thanks,
Mac
jimh posted 03-19-2006 11:27 AM ET (US)
In the U.S. most outboard motors are rated for horsepower according to the ICOMIA 28-83 standard. You can read this standard in the REFERENCE section:
http://continuouswave.com/whaler/reference/ICOMIA28-83.html
I do not recall any mention of a rating at continuous full throttle.
When the EPA tests outboard motors for emission compliance, it operates them at various levels of power (relative to their rated power). The schedule they use has been chosen to mimic the typical boat operation. I do not recall the precise details, but I believe operation at full throttle is assumed to only occur for a small percentage of the engine operating time.
As far as I know, and forgive my ignorance on this topic, I do not believe any outboard is rated for continuous operation at full throttle. These engines are carrying rather long warranty protection, but I don't think any of them will run 7-years at full throttle and survive.
highanddry posted 03-19-2006 05:54 PM ET (US)
Actually small aircraft engines such as the Lycoming 320/360 cu in engines are rated for full power for their 2,000 hour TBO. Of course, that may not be entirely wise, high power levels are common with cruise power of 75%. I just built up, for my own use, a custom built Lycoming based IO360, custom cam, flowed heads, high compression, blue printed and balanced, it is fully capable of continuous operation at WOT making approx 210 to 220 horsepower.
I have operated outboard powered ski boats for hundreds of hours at near full throttle--approx 5,000 RPM. Such engines often live longer than engines that are treated like a baby, are cleaner when pulled down, less carbon etc.
Teak Oil posted 03-20-2006 06:39 PM ET (US)
An outboard run at 75-80% with occasion WOT blasts will usually live a long and happy life.
Engines run at WOT all the time are called race egines and there is a reason why they are rebuilt every season or two

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Author	Topic: Outboard Motor Power Rating: Continuous Full Throttle
bmclernon	posted 03-19-2006 11:18 AM ET (US) I notice throughout all the performance literature Mercury establishes certain performance parameters for a specified RPM or power setting. My experience with SEL airplanes tells me after take-off you don't go blasting around WOT. Crusing or continuous power is usually much lower (50 - 75%). Are modern outboards rated for continuous WOT operation? If no, what are specifications for Continuous power operation in modern outboards (2-stroke and 4 stroke). Example: Mercury mid-range OBs. Thanks, Mac
jimh	posted 03-19-2006 11:27 AM ET (US) In the U.S. most outboard motors are rated for horsepower according to the ICOMIA 28-83 standard. You can read this standard in the REFERENCE section: http://continuouswave.com/whaler/reference/ICOMIA28-83.html I do not recall any mention of a rating at continuous full throttle. When the EPA tests outboard motors for emission compliance, it operates them at various levels of power (relative to their rated power). The schedule they use has been chosen to mimic the typical boat operation. I do not recall the precise details, but I believe operation at full throttle is assumed to only occur for a small percentage of the engine operating time. As far as I know, and forgive my ignorance on this topic, I do not believe any outboard is rated for continuous operation at full throttle. These engines are carrying rather long warranty protection, but I don't think any of them will run 7-years at full throttle and survive.
highanddry	posted 03-19-2006 05:54 PM ET (US) Actually small aircraft engines such as the Lycoming 320/360 cu in engines are rated for full power for their 2,000 hour TBO. Of course, that may not be entirely wise, high power levels are common with cruise power of 75%. I just built up, for my own use, a custom built Lycoming based IO360, custom cam, flowed heads, high compression, blue printed and balanced, it is fully capable of continuous operation at WOT making approx 210 to 220 horsepower. I have operated outboard powered ski boats for hundreds of hours at near full throttle--approx 5,000 RPM. Such engines often live longer than engines that are treated like a baby, are cleaner when pulled down, less carbon etc.
Teak Oil	posted 03-20-2006 06:39 PM ET (US) An outboard run at 75-80% with occasion WOT blasts will usually live a long and happy life. Engines run at WOT all the time are called race egines and there is a reason why they are rebuilt every season or two