Silvertip
Supreme Mariner
- Joined
- Sep 22, 2003
- Messages
- 28,771
Re: 4stroke making oil
That is NOT what I said. I said an incorrect prop (one with too much pitch) is lugging the engine. That means it is lugging REGARDLESS what rpm you are running. Your engine has one gear -- not multiple gears like a car. That gear must get the boat out of the hole, on plane, and not over-rev or underrev (lug). The engine manufacturers have an RPM BAND they want the engine to run in. That is determined primarily by the prop installed. Engines over about 40 HP are not even shipped from the manufacturer with a prop because they have no idea what boat the engine will be installed on. A pontoon for example takes a very different prop than a light V-hull. Step one in diagnosing the making oil issue is to make some WOT runs with what you consider an "average" load. Note the WOT throttle RPM. If it is higher than the manufacturer recommends (normally around 6000 rpm) then you have too little pitch and that would not be the cause of making oil. If the engine does not get within 300 - 400 rpm of the upper end of the band, you have too much pitch and a different prop is in order.
Regarding continued operation at WOT is a no-brainer. Run continually at WOT and the engine will not run as long as it would if run at 75% - 80% throttle. The engine must still turn the same number of times to reach a destination regardless of the throttle setting, but an engine (any engine) is under less stress at part throttle than it is at WOT throttle. Your engine is designed to run at 6000 rpm. If it wasn't, the manufacturer would have specified a lower number. The manufacturer also has installed an electronic device called a "Rev Limiter". If the high end of the band is specified at 6000, the rev limiter would be set for about 6400 at which point the ignition is interrupted to prevent reving higher than that.
That is NOT what I said. I said an incorrect prop (one with too much pitch) is lugging the engine. That means it is lugging REGARDLESS what rpm you are running. Your engine has one gear -- not multiple gears like a car. That gear must get the boat out of the hole, on plane, and not over-rev or underrev (lug). The engine manufacturers have an RPM BAND they want the engine to run in. That is determined primarily by the prop installed. Engines over about 40 HP are not even shipped from the manufacturer with a prop because they have no idea what boat the engine will be installed on. A pontoon for example takes a very different prop than a light V-hull. Step one in diagnosing the making oil issue is to make some WOT runs with what you consider an "average" load. Note the WOT throttle RPM. If it is higher than the manufacturer recommends (normally around 6000 rpm) then you have too little pitch and that would not be the cause of making oil. If the engine does not get within 300 - 400 rpm of the upper end of the band, you have too much pitch and a different prop is in order.
Regarding continued operation at WOT is a no-brainer. Run continually at WOT and the engine will not run as long as it would if run at 75% - 80% throttle. The engine must still turn the same number of times to reach a destination regardless of the throttle setting, but an engine (any engine) is under less stress at part throttle than it is at WOT throttle. Your engine is designed to run at 6000 rpm. If it wasn't, the manufacturer would have specified a lower number. The manufacturer also has installed an electronic device called a "Rev Limiter". If the high end of the band is specified at 6000, the rev limiter would be set for about 6400 at which point the ignition is interrupted to prevent reving higher than that.