Hello, new to the site. I recently bought a used boat and I'm trying to maximize its performance. The boat is a 1988 Lowe Big Jon, 14ft. The motor is a mid 90's Johnson 15 hp. It is missing the number plate so I don't know the exact year. It has some of an electric start kit on it and there are a few pieces missing and it was clearly "tinkered" with. Altitude is 4000 feet. I weigh about 270 and have 6 gallons of gas, trolling motor and battery aboard.
Just to make the story long, at first I couldn't get more than 13 mph out of it. I checked the carb and it appeared that the throttle plate wasn't opening all the way. I adjusted that and got 16 mph with very slow acceleration. Turns out it had a 9.5x12.5 prop on it.
So I ordered up a Solas 9.25x10 prop and a cheap tachometer. Now it still gets 16 mph. 5500 rpm wot. Acceleration is good and it gets on plane quickly. Changes to the trim didn't get any more speed. The motor seems to be running well and it starts easily. Spark plugs look good.
Does this sound normal? I see a lot of people on the internet claiming much higher speeds from a similar set up. Prop slip seems a little high. I could go to a 9 pitch but I don't know if that would help.
Thanks
Just to make the story long, at first I couldn't get more than 13 mph out of it. I checked the carb and it appeared that the throttle plate wasn't opening all the way. I adjusted that and got 16 mph with very slow acceleration. Turns out it had a 9.5x12.5 prop on it.
So I ordered up a Solas 9.25x10 prop and a cheap tachometer. Now it still gets 16 mph. 5500 rpm wot. Acceleration is good and it gets on plane quickly. Changes to the trim didn't get any more speed. The motor seems to be running well and it starts easily. Spark plugs look good.
Does this sound normal? I see a lot of people on the internet claiming much higher speeds from a similar set up. Prop slip seems a little high. I could go to a 9 pitch but I don't know if that would help.
Thanks
