I only use my electric for maneuvering around or through structure when stealth is important or I'm in shallow water. When trolling I use my 4 stroke. When foward trolling, speed is subjective to the species & mood of the fish. Try your troll at idle on your motor. While trolling, make s turns of medium to small size, just make sure they are big enough to turn your lures, not too big to cross your lines. If you find your getting hit during turns, notice which side off the boat is getting hit. If the inside lure is always getting hit, slow your troll. If the outside is getting hit, increase your troll. Some lures require a faster troll to get proper action, always check the lures action next to the boat at your trolling speed to make sure your getting proper action and nothing is wrong with your bait. You will learn what fish want at different times of the year. Right now, I troll SLOW. Cold water usually = sluggish fish. Most times I troll about 1.8 mph. I also use speed to contour troll lead and downrig. Speed will decrease the depth of your lead line or downrigger weight. As you see a hump or decrease in depth on your finder, increase speed and your lures will come up, if you find you get hits at that time, determine if, 1. was the strike due to your speed?
2. was the strike due to the structure?
3. was it maybe a combination of both?
When you find what works, reproduce as much as possible. I usually will always increase and decrease speed on a random basis. Change it up, when not getting hits. Even the occasional stall to stop the baits. Sometimes a sudden change will get a strike. When your casting a lure you usually impart some type of action to the bait. Do the same with your troll.