Scared to go WOT too long
10-16-2011, 06:29 PM
#12
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10-16-2011, 07:31 PM
#14
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some more info
I have installed an oil temp guage and have senders for oil temp before and after the cooler (changed by a switch on dash panel)
When I run it hard (at or near wot) the oil temp rises to about 220 before the cooler and 190 after. She'll cool right back down when I slow to cruise speed.
WOT a/f ratio is 12.5
When I run it hard (at or near wot) the oil temp rises to about 220 before the cooler and 190 after. She'll cool right back down when I slow to cruise speed.
WOT a/f ratio is 12.5
10-16-2011, 09:53 PM
#17
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I second that, the longest I have held my boat at wide open throttle at its current power level was when the blower belt was slipping and I could only get 90-92 mph out of it, held it for 5 minutes. When it had less power (blown 502) I held it at wot for 25 minutes once but it was only going 80-82 mph, Smitty
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10-18-2011, 06:34 PM
#19
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Depends on the motor.
I had a 1969 Evinrude 33hp twin. If it was running, it was wide open. It ran like this for probably a million hours, possibly two million (yes this is an estimate). My guess is that wherever it is, it's still running.
Jet Ski/Waverunners run WOT for long periods of time, especially the ones with less horsepower. The 701 Yamaha motors were known for reliability and longevity and they put them in the heavy XL hull for rental skis, which were wide open all day long every day.
Lawnmowers run WOT all day/week/season long. Their WOT is 3500 rpm though.
Had a 21' Wellcraft with a 350/260hp Mercruiser. We went all summer at WOT - after a couple hundred hours of constant 4600rpm, the compression was down and the cylinder bores had a ridge at the top of the stroke.
Friction and heat are the enemy of a motor. If you can keep metal parts from rubbing against each other, and you can keep the lubricating fluids within their temperature ranges, then motors last a darn long time.
Valvesprings, though, make heat and get weak. Flat tappet cams wear out. Piston rings wear. Oil gets contamination in it and loses viscosity with heat, use, and gas blowby.
If your motor can run 6000 rpm without having any internal hotspots (which you can't necessarily tell from the oil temp), and shows an excellent result on an oil analysis when you change it, keeps the EGTs steady and safe, and maintains an even coolant temp in the block and heads, then you can run it at 6000 a long time with no probs.
The issue comes in, though, when you run the motor PAST the pojnt where all of those factors remain optimal. Each engine build will differ in where those danger points are.
MC
I had a 1969 Evinrude 33hp twin. If it was running, it was wide open. It ran like this for probably a million hours, possibly two million (yes this is an estimate). My guess is that wherever it is, it's still running.
Jet Ski/Waverunners run WOT for long periods of time, especially the ones with less horsepower. The 701 Yamaha motors were known for reliability and longevity and they put them in the heavy XL hull for rental skis, which were wide open all day long every day.
Lawnmowers run WOT all day/week/season long. Their WOT is 3500 rpm though.
Had a 21' Wellcraft with a 350/260hp Mercruiser. We went all summer at WOT - after a couple hundred hours of constant 4600rpm, the compression was down and the cylinder bores had a ridge at the top of the stroke.
Friction and heat are the enemy of a motor. If you can keep metal parts from rubbing against each other, and you can keep the lubricating fluids within their temperature ranges, then motors last a darn long time.
Valvesprings, though, make heat and get weak. Flat tappet cams wear out. Piston rings wear. Oil gets contamination in it and loses viscosity with heat, use, and gas blowby.
If your motor can run 6000 rpm without having any internal hotspots (which you can't necessarily tell from the oil temp), and shows an excellent result on an oil analysis when you change it, keeps the EGTs steady and safe, and maintains an even coolant temp in the block and heads, then you can run it at 6000 a long time with no probs.
The issue comes in, though, when you run the motor PAST the pojnt where all of those factors remain optimal. Each engine build will differ in where those danger points are.
MC
10-18-2011, 07:46 PM
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The real answer to this question is directly related to how fat your wallet is.
Bottom line. Rich guys have spares of everything waiting for a failure and they have guys to do the work for them.
Like most things in life, it comes down to money.
Bottom line. Rich guys have spares of everything waiting for a failure and they have guys to do the work for them.
Like most things in life, it comes down to money.
