my 1985 20 hp evenrude needs to be set to almost full throttle to start her up, and set at anything less than 50% she dies, basically won't idle at proper low setting and when running at full throttle seems like she is only at running at approximately half speed. I have a 14 ft aluminium boat and with two people and my gear i can only get up to 17 mph if i'm lucky, should be going alot faster than that should i not?