prop placement

[fatboy0054]

How far down below the trans can the prop go . I need a starting point 78 Power shift maxius. 15 ft - 500 cad Thanks! MR Thunder for the other important infor ,thanks

 

[c chardt]

I was told that max below the transom is 5" avrage is about 2-3" to blow the back wash out.

 

[Waterthunder]

I would set the prop down 5 inches below the transom. A lot of aircraft guy’s will tell you not to do this but remember your trying to over come a problem an aircraft will never have. Are you going to run a Maxumus or a Power Shift Three blade. Because I built a friend of mine 500HP plus 383 SBC for about 7 years ago. I begged and pleading with him not to put a 2 blade Maximus on his boat the boat was running a Warp Drive. Well he had everyone whispering in his ear about how much better a Maximus was over the three blade Power Shift. So he put a Maximus on a three year old boat that was in perfect condition. Well in about a month the cage was junk all the tubing and welds were cracking. His rudders were even getting damaged. I will admit the prop pushed hard but I swear you could hear the air pulsing of the blade and the harmonics that a two blade wide blade put out are horrendous. You could watch the rigging and rudders bouncing back and forth at Idle. See a prop that wide doesn’t balance well with only two blades. Anyway now he would do anything to have a Power Shift three blade to put on what’s left of his boat. I’m guessing but you might have a few people recommending the Maximums if so I bet they are running direct drive. In that case there a great low RPM prop. However if you run a gear box to turn more RPM’s why would you run a prop that’s designed for max efficiency at lower RPM’s. I’m honestly trying to help out I like to share any helpful information I may have. So if I’m to over bearing just tell me. I just hate to see the same mistake made over and over and over.

 

[fatboy0054]

YES sir Mr thunder - 3 blade Max .they said 80 instead of 78 on the three .blade I told them give me about 2 weeks . I geuss they dont sell very many 78 -3 blades .or dont make them . dont worry about giving your views to me . Tickels the s--- out of me some one is trying to help . I am my own worst fear! I really thank for your input .so i will do 2.38 3 blade max 5 in below trans Like you said i I will make things ajustable so i can tweet things . I wil have to start sending you a check ever month . Thank you very much for letting me in the circle :lol:

 

[Waterthunder]

No problem at all I'm glade to be of help. Now you are running the Power Plus series prop right. You don't need to run a three blade Maxumus unless your making 800 Plus HP.

 

[fatboy0054]

NO- I was thinking the 3 blade max they said i could run the 3 max . Dont no - see thats why i ask ! I would like to keep the rpms at 4800 to 5000 .for longgevatee-- ? I know no spelling --with a 2.38 -3 -b--PS-plus that would give about 2100 @ prop. will that give me enough prop rpms .I am tring to get as low noise as i can . I seen a 2 blade max and it was real hush - would get close to 90@50 with alot of push . I got have the most of push to go to the circle K down the road. you no what i mean , speed is nothing Igot to go dry about 1000 ft before it gets wet .cant afford a trailor.thanks Mr thunder

 

[passtime]

how far away from the transom, not below, should the prop be?

 

[fatboy0054]

I have found threw these guy s on here . 6in works for me for a wide prop . Harmonics was bad any closer .Its apain but worth it . Hopfully some one with more , will tell you . This the first auto motor boat . but liking it .A lot of real knowable people on here.