Quote:
Originally Posted by klem
As you mentioned, lugging is bad. Lugging is trying to get too much power out of each combustion cycle by simply forcing more fuel in. What this means is that rather than having the work done by the engine spread out over more combustion events, it is concentrated greatly increasing stress.
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I'm not sure about the stress issue considering that I'm backing off about 20% from the WOT setting. Seems like if the WOT was 3600 rpm and I backed off 20% from that number, stresses induced on the engine should be similar? No calculations to back that up. Anyway that point about the jeep is that I can hear the engine "lugging" whereas with the Perkins it sounds "happy" at the lower rpm even pushing into a head wind. I'll probably reduce that pitch back to 12 inches approx. so to get more horsepower rating. At 2000 rpm the shaft hp is 8 whereas at 2500 it's 14. (3000 is 21)
One other thing that I noticed about rpm and WOT. When tied at dock my WOT rpm is about 150 rpm less that when out on the water. This I can understand since less force is needed to move the boat underway vs tied to the pilings. Not sure if I said that right. Anyway expect that I can achieve a higher WOT setting still if I'm going against a stiff current. (flow past the prop allows the prop to work less and I've seen around 2600 rpm on WOT) Hull spreed through the water would still be the limiting factor so there is a limit to how much rpm could be gained going against the current.