Hi, Im new to jet boats. I bought a beat up 1978 glastron carlson cv-23. It has a ford 460 and a Berkly 12JE.
The boat also has hydraulic trim tabs. I finally got the thing into the water to do a wet test. It idled great through the marina and steered well. But when given gas at higher rpms it was very slow to get up to plane. I could hear it was cavitating bad, but eventually planed out. However when we made a turn at speed it slowed down to a crawl and the engine rpms started to rise. Before I could back down on the throttle, the temperature spiked at like 280 degrees and the engine quit.  Well long story short...we had a nice afternoon of floating til the wind pushed us against the rocky beach....and eventually towed to the marina.
I crated up the jet and sent it in to berkly for a rebuild. 
    Question= If the trim tabs were all the way down could that have caused the jet to cavitate to the point where no water was going to tne engine ?
     And I would like to install a jetovator, How would the trim tabs affect the performance?

yep to any of the above. There is no valve inline, but im adding one. The packing was loose, it could draw in air...but that much too overheat the engine, and slow the boat The keyway could have sheared...the boat had not run for serveral years.  The impellar was alil dinged up, but I figured not enough to cavitate that much, Oh well we will see when I install the new rebuilt pump. Thanks for the ideas. Next wet test Ill be sure to bring a sail.