90HP to 140HP Johnson V4

[mwgriffin]

I've recently acquired a 90HP Johnson V4 (circa 1985-1990). The previous owner said that they had modified it by replacing some things from a higher HP motor - i.e. heads, carbs, ignition, exhaust. The net effect of these changes was to increase the HP to 140. <br /><br />I saw a similar change described in another post regarding 90-115 HP Evinrude. In this post there were references to WOT throttle setting, and how this setting was important to realize the potential of the changes. What is WOT throttle setting - i.e. butterflies and timing, and what should it be.<br /><br />Also does anyone else have experience with such an engine that they can share. I would like to know what the operating RPM should be, etc...

 

[Mod2]

Re: 90HP to 140HP Johnson V4

Welcome to iboats MW. Normally this is a general discussion post but you have several issues that can best be handled by our wrenches over in Johnson/Evinrude Forum. I'll move it there.

 

[Dhadley]

Re: 90HP to 140HP Johnson V4

Welcome!<br /><br />Were the ports changed to the 140 specs (port timing and port area)?

 

[jimmbo]

Re: 90HP to 140HP Johnson V4

We are refering to the 99.6 cu.in. block. To make a crank rated 90 into a crank rated 115 you have to port the block, change the heads, and change the carbs. To make this or a crank rated 115 into a crank rated 140 you now have to add the bubbleback/tertleback exhaust housing and inner exhaust tubes. Some years also used different exhaust tuning tubes in the midsection. BTW. the old 140 never put out more than 128 hp anyway but it was within the +/- 10% of its 140 hp rating. The 140 was later prop rated and called a 115.