Re: 69' 9.5 performance question
I also have a 9.5, although mine is a 67, but should be the same. I had some problems with mine, but with the help of this great forum, are all resolved now.
So, from my recent work on my motor which did similar, check the following:
1) When at WOT, is the carb fully open (look down into the throttle body opening)
2) Check the main jet which is in line with the fuel bowl drain plug, mine was pretty blocked. Removed the drain plug, then use a narrow straight blade screwdriver to get deep into the hole to unscrew the main jet.
3) Check the low speed mixture. Get the motor warm, put it in neutral with the RPM up a little so it is off of idle, strictly should be around 450 rpm if you can measure the rpm. Pull or pry off the low speed mixture knob so you can rotate it more than the stops on the knob. With a pair of pliers rotate the splined end of the shaft clockwise a little at a time until the engine starts to idle rough, note that position. Turn it back counterclockwise until it does the same and note the position. Then set it mid way between these two point sand push the knob back on in the center position (make sure you don't lose the spring washer behind the knob). The base starting point for the low speed screw is 3/4 of a turn out from dead closed.
When I rebuilt my carb to fix the lack of high rpm, I found it was still sluggish until I reset the low speed screw. Not sure why it really affected high speed, but it did, it ran faster than ever after cleaning the main jet and setting the low speed screw. Oh yes, when you make the adjustments, do them slowly and give the motor a little time to react to the mixture change.
The max rpm should be around 4,500 rpm, look at the plate on the side of the outboard mount.
Mine sounds fast now, not like it did before, she screams pretty good.
Tony
