Johnson Horsepower Question (50,60,70)

[pshell]

I have a technical question on 1985 and newer 3 cylinder Johnson and Evinrude- 50HP, 60HP, 70HP. All three horsepowers use the same pistons, rings, rods, cranks, and reed valves. How do they get a 20HP difference with the same parts. Is it carbs, carb jets, port timing, or a combination of these. I am rebuilding a 60HP and have noticed all three horsepowers use the same parts. Is it possible to make my motor(1993 60HP Johnson) a 70HP. Please help. Thank you.<br />Philip Shell<br />pshell@midtnn.net

 

[Spidybot]

Re: Johnson Horsepower Question (50,60,70)

This topic comes up now and then.<br /><br />Bottom line is, that it is not worth the money as alterations involve many small and big things. In your case it's different as you have to buy parts anyway, but getting an idea of the total cost is a must.<br /><br />The rule says 'if you want more power, buy a more powerful motor'.<br /><br />At the end of the day you may end up in worries and problems not worth the extra 10 hp.

 

[Dhadley]

Re: Johnson Horsepower Question (50,60,70)

As UU stated, this comes up all the time. There are small differences but you would have to have a high performance type hull design to get any benifit. Believe it or not sometimes the motor is simply rated at a lower RPM. Keep in mind you have the same bore/stroke and gear ratio. The same thing happens when someone trades in a 50 on a 70 and are wondering why they run the same prop and about the same speed. <br /><br />Now, if you had a 2 cylinder 50 and went to a 3 cylinder 70 -- yes you would see a greater difference. Lots more torque. <br /><br />If I was rebuilding a 93 60hp and had to change the cylinder head, I would certianly opt for the 70 head but I would not spend the bucks for it otherwise.<br /><br />Sorry!