I just finished restoring a '64 Chris Craft wood boat. We have had it in the family for over 50 years now. It has the very first '63 Mercruiser I stern drive on it.
After getting it in the water, I've had a ton of trouble with prop ventilation/cavitation. I started with an old mercruiser prop 13" x 15" on it (48-32390A3). Any RPM over ~2500 will take ZERO steering wheel input without revving to the moon. Even while running straight it will start to over rev in slightly choppy water.
I took a hard look at the prop, and it appears it had been hitting the driveway or something during running, because it had a sharp burr on it around the widest circumference. Probably about .050" or so.
I had another old 13" x 17" Michigan Wheel PR-157 to try, so I put that on there. It is significantly better, but still will not make any reasonable turns over about 3000rpm or so. With two people tubing on the boat today, it would not achieve full throttle without over revving either. The 13" x 17" is a dog for sure on this boat too.. 1mph loss in top speed, and killed the bottom end.
This boat has no power trim adjustments. It's currently trimmed full down on the manual plate. The cavitation plate on the drive is roughly even with the bottom of the keel (no adjustments there).
What are my options to improve this boat. Will trimming it up help slightly by getting the nose up/stern down? It was noticeably better with a person sitting at the rear of the boat today, so that gave me the idea.
Since I'd like to put another prop on it, would buying something with some "cup" in it help? The props I have are 1965-85 era, so hardly modern technology!
Please let me know if I can answer any further questions, I'm open for suggestions, and appreciate all the help I can get!
After getting it in the water, I've had a ton of trouble with prop ventilation/cavitation. I started with an old mercruiser prop 13" x 15" on it (48-32390A3). Any RPM over ~2500 will take ZERO steering wheel input without revving to the moon. Even while running straight it will start to over rev in slightly choppy water.
I took a hard look at the prop, and it appears it had been hitting the driveway or something during running, because it had a sharp burr on it around the widest circumference. Probably about .050" or so.
I had another old 13" x 17" Michigan Wheel PR-157 to try, so I put that on there. It is significantly better, but still will not make any reasonable turns over about 3000rpm or so. With two people tubing on the boat today, it would not achieve full throttle without over revving either. The 13" x 17" is a dog for sure on this boat too.. 1mph loss in top speed, and killed the bottom end.
This boat has no power trim adjustments. It's currently trimmed full down on the manual plate. The cavitation plate on the drive is roughly even with the bottom of the keel (no adjustments there).
What are my options to improve this boat. Will trimming it up help slightly by getting the nose up/stern down? It was noticeably better with a person sitting at the rear of the boat today, so that gave me the idea.
Since I'd like to put another prop on it, would buying something with some "cup" in it help? The props I have are 1965-85 era, so hardly modern technology!
Please let me know if I can answer any further questions, I'm open for suggestions, and appreciate all the help I can get!