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1989 20 HP Johnson power upgraded to 25 HP for zero dollars
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<blockquote data-quote="Johny25" data-source="post: 354109" data-attributes="member: 7791"><p>So you have an 89' 20hp which you turned into a 25hp correct. The 20 and 25hp have same recommended RPM range 4500-5500 RPM in that year. My advice would be to get real close to the 5500 RPM when you have the lightest load you typically run in your boat. And don't worry if you turn 5600-5800 it won't hurt these motors. In fact the 30hp runs at 5800 and it is just different carburetor. </p><p></p><p> Your gear ratio is a 13:28 also known as 2.15:1</p><p></p><p> Get a tach and we can help you get the correct prop. But by looking at the info you already have given me I think you may be OVER propped already.</p><p></p><p> If you are doing 38kmh (23.5mph in my language lol) with a 2.15:1 gear ratio and a 13 pitch prop then it is HIGHLY likely you are only running at around 4700-4800 RPM. These motors produce the 25hp at 5000-5200 and run way better over 5000k</p></blockquote><p></p>
[QUOTE="Johny25, post: 354109, member: 7791"] So you have an 89' 20hp which you turned into a 25hp correct. The 20 and 25hp have same recommended RPM range 4500-5500 RPM in that year. My advice would be to get real close to the 5500 RPM when you have the lightest load you typically run in your boat. And don't worry if you turn 5600-5800 it won't hurt these motors. In fact the 30hp runs at 5800 and it is just different carburetor. Your gear ratio is a 13:28 also known as 2.15:1 Get a tach and we can help you get the correct prop. But by looking at the info you already have given me I think you may be OVER propped already. If you are doing 38kmh (23.5mph in my language lol) with a 2.15:1 gear ratio and a 13 pitch prop then it is HIGHLY likely you are only running at around 4700-4800 RPM. These motors produce the 25hp at 5000-5200 and run way better over 5000k [/QUOTE]
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1989 20 HP Johnson power upgraded to 25 HP for zero dollars
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