How do i set a manuel jack plate

once again i got a 1986 bumble

once again i got a 1986 bumble bee with a 1979 mercury 150 on back. had a jack plate on back when i bought it. guy that owned it before me has it jacked all the way down which has got the prop sitting about a foot or more below the bottom of the boat. how do i set this or know how much to bring it up. someone once told me that i should be running so many rpm's but my last post was about how do i fix my rpm gauge that is not working right. would it hurt if i brought it up some. i heard not to bring up to high or else water would not get into bottom and would burn engine up. any info would help. until i get rpm gauge fixed how high can i bring it up so that it will run better. right now with two people in voat. it puts the exhaust under water which causes motor to bog down.

"I think you should monitor th

"I think you should monitor the pressure from the water pump. As long as it is high enough, you can jack ut up further without overheating the enginge. I don't know the minimum required pressure, but someone else on this board might.
Robert"

"Jimmy, Start with the motor&

"Jimmy, Start with the motor's antiventilation plate even with the bottom of the hull. You should not have any issue with cooling in this position. If it doesn't ventilate, you may raise it up for better speed. It is best to have a water pressure gauge, but if you don't keep an eye on the telltale to make sure it pumps at it's raised location, as you raise it up."