I have a 10 year old 25 Hp Merc on the back of my jon boat. It starts easy and idles well. The problem is when I run at full throttle for more than a couple minutes. When I do so, the RPM’s will shoot up super high. In order to get the RPM’s back to a normal level, I need to take the boat off plane. I can then get back on plane and run for a couple more minutes. Anyone have any idea why the RPM’s would shoot up so high?
It sounds to me like your motor tilt setting is set too-high. Try setting it down a notch. The same thing happens with motors that have power tilt & trim when you trim it up too-far. What is happening is that you prop is not digging into the water enough.
Eyehunter
I thought that was a possibility too, but then I don’t understand why it wouldn’t happen as soon as I got it on plane running full throttle.
Mine will do the same thing after I have been up on plane for a while. My prop is biting-in good until I hit wake or turn a corner which causes the prop to lose it’s bite and free spin. Then all I do is touch the down switch a bit until the prop is back in the water where it is supposed to be.
Eyehunter
You must be logged in to reply to this topic.
