Re: 1968 9.5 evinrude hp power increase?
Hi Craig,<br /> Rather than looking for a modification to add power, I would recommend making sure you're getting all the rated horsepower from the get-go. In all likely-hood, your 35-year old motor isn't even putting out 9.5hp. A good start would be to run some decarboning agent through it (OMC Engine Tuner, Sea Foam, etc.) to clean up the rings, exhaust ports, etc. After doing this, run a compression test. Are both cylinders at least 90 psi, and within 5% of each other? If you're on the far side of 110 psi, all the better.<br /> Next, borrow an inductive tachometer to see if you're pulling the optimum revs out of your motor. Don't quote me on this, but I think your motor is rated at 4500 RPM. If you're not pulling that many revs, you might need to look for another prop. That motor has aluminum rods and won't be very happy running at the 6500 revs described above. Might go for a short bit, but I wouldn't make it a habit.<br /> Is your existing prop in good shape? Any dings, scrapes or bends will rob you of power. How about the skeg? Rest of the lower unit? <br /> Often overlooked is the throttle linkage. Your 9.5 has a lot of linkage to wear out. Lots of pieces to get a little loose and keep the throttle from fully advancing. Is the tiller throttle moving the magneto to the stops and fully openin the carb butterfly?<br /> I can't tell you how many times I've had people bring me motors they want "souped up", only to find it needs a basic tune-up and check-up to gain back it's original top end. Good luck!<br />- Scott
