Looking through my service bulletin collection I came across this and don't know if it had been shared before but thought I would anyway. I find test wheels very helpful in diagnosing problems or setting full throttle timing accurately. I use a fiberglass tank that is 10' long X 2' wide X 2 1/2' deep. We cover the back 7 ft when running them to prevent water blow out but with that length it isn't that bad and we suffer no cavitation of the prop.
From the Service bulletin:
"NOTE: These test props have been developed because of Dual Exhaust Lower Units. Force test wheels previously used will ventilate on a Dual Exhaust Lower Unit."
model proop p/n pitch reduced dia. rpm
150 hp P685-1 17 11" 5150-5200
120 hp P685-1 17 9 7/8" 5200
90 hp P685-1 17 9" 5000-5150
70hp 816704A40 13 9" 5000
Next time you get a mauled up prop in that you replaced and it is one of these, send it off to you prop shop and have them cut it down. My shop does it for free---of course I send them about 100 props a year to get repaired, polished, etc.
From the Service bulletin:
"NOTE: These test props have been developed because of Dual Exhaust Lower Units. Force test wheels previously used will ventilate on a Dual Exhaust Lower Unit."
model proop p/n pitch reduced dia. rpm
150 hp P685-1 17 11" 5150-5200
120 hp P685-1 17 9 7/8" 5200
90 hp P685-1 17 9" 5000-5150
70hp 816704A40 13 9" 5000
Next time you get a mauled up prop in that you replaced and it is one of these, send it off to you prop shop and have them cut it down. My shop does it for free---of course I send them about 100 props a year to get repaired, polished, etc.