How fast should my boat be?

So I'm running a 70's Sears 12' Semi V, with no weight in it other than me, the motor, and 3 gallons of gas. I'm about 220lbs, the motor is 77lbs. The motor is a 1977 15hp Johnson.

Today I was averaging 20mph topped out, and hit 21mph at one point according to my GPS.

This seems a bit slow? Anyone have any thoughts?

Currently the cavitation plate is about 1.5-2" below the boat. I know this isn't helping anything, but I was assuming the boat would do 25-29mph.......would it significantly speed the boat up if I raised things 2"?

Growing up we had a 12' Semi V with an Elgin 7.5 and it would get up on plane with my father, my brother and myself with our gear in it also. It probably ran about 15mph with an estimated 600lbs in it. My 14' Duracraft flat bottom with a 9.9 Evinrude probably runs in the 18-20mph range with myself and my gear in it. I am 240lbs with about 150lbs gear with a three gallon tank. Never had a GPS in it to check for sure. It jumps up on plane very quickly and runs pretty quick. So 20-21mph in yours sounds about right to me.

On my 1240 vee with my 15 hp (same motor you have)I get about 26mph.

crazymanme2 said:

On my 1240 vee with my 15 hp (same motor you have)I get about 26mph.

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Thanks for the input.

Is your cavitation plate exactly level with the bottom of the boat?

Nope,it's about 1.5 above but if your is 1 above that should be good.Each boat is different how high you can raise motor.Just make sure it's pumping water.

crazymanme2 said:

Nope,it's about 1.5 above but if your is 1 above that should be good.Each boat is different how high you can raise motor.Just make sure it's pumping water.

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Mine is actually about 1.5" below the bottom of the boat. I'm thinking this is the problem, because the motor really seems to run strong. It could also be a prop issue too I guess......I'm guessing the stock prop is designed for a boat that weighs a bit more. Mine really gets on plane quick......a bit more prop might give me better top end speed and still get up quickly.

I have a 14' sea nymph big water. I get to about 21-22 mph gps. 6 gallon gas and I wiegh just 190#. I've tried moving the gas forward to see if it would help with speed , but it dosen't. I will help the steering though. My cavitation plate is just below the botom of my boat. Hope this helps. Spin

spinfisher said:

I have a 14' sea nymph big water. I get to about 21-22 mph gps. 6 gallon gas and I wiegh just 190#. I've tried moving the gas forward to see if it would help with speed , but it dosen't. I will help the steering though. My cavitation plate is just below the botom of my boat. Hope this helps. Spin

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Is your motor a 15?

I think yous are getting about the rite speeds when running 15hp.15HP isunt much HP and yous can only get so much from it.

yes 1985, 15 hp johnson