proper trim/prop selection

[joseph1980]

I recently purchased a 4 blade 18 pitch comp prop form my 96 bayliner 1950 with a 3.0 liter mercruiser. (the previous prop was a 19 pitch 3 blade aluminum, however i never ran the boat with this prop as it was missing a big piece out of one blade) My question is when the manufacturer listed the max operating rpm at 4400-4800, was this with the prop trimmed all the way in the water? At wot with prop trimmed all the way in i'm pulling about 4100 rpm. If i trim it out of the water some i can get in that range and one time i came out to far and went over. I guess my question is basically does it sound like my prop is a good selection? I use the boat mainly for tubing and watersking.

 

[Realgun]

Re: proper trim/prop selection

Heres the deal. IF you are running in the recommended range of the motor you and your at a normal load you want to be near the top of the range. If your at the bottom and you heavy that fine. Triming the motor for Max RPM spped is how you get you Readings. Now if you feel the boats not up to skiing then you could lower the pitch 2 inches and get a better pull however you will need to be careful not to over rev the motor.<br /><br />A husltle prop would be great in this situation. You just change the prop not the housung and you can have a slow prop to pull skiers with (lower pitch) and a Fast prop (Higher pitch)for those WOT and long cruises. Better mialge that way as long as your in the range the motor is recommended for.

 

[Realgun]

Re: proper trim/prop selection

As to trim you will need to raise the motor till its running at max rpm and is not cavitating. Also if the boat starts to porpose then go down a we bit on the trim as thats probably the sweet spot right there.

 

[danie]

Re: proper trim/prop selection

Joseph<br />Can I ask what you meant by "..one time I came out too far and went over." <br />Did you flip the boat and went into the drink?<br />D

 

[joseph1980]

Re: proper trim/prop selection

by "going over" i meant i exceeded the max rpm's. I went up to about 5 grand.

 

[walleyehed]

Re: proper trim/prop selection

5K ain't gonna hurt it....ya need to see just how far it will go with proper trim to see what we need to recommend...