prop change help ! ! !

[coby-5]

i have an 04 90 hp mercury.the stock prop is:12 3/4 X 21.....i want to put a SS prop thats is 13 1/4 X 21.....what wil the 1/2 larger dia. do?<br />thanx for any and all help

 

[walleyehed]

Re: prop change help ! ! !

Allow a higher mounting height of the engine for one...most likely will give a little better hole-shot, but for the most part, you may need to raise the engine one hole and test.<br />Try it out first as-is and see what ya get and we'll go from there.<br />Guess we need some other info too, like max RPM now, what type of boat, etc.

 

[DJ]

Re: prop change help ! ! !

Bass,<br /><br />Before you change, make sure you are within your top rpm range, as dictated by Mercury. If you are below, you are "lugging" the engine. Which is NOT good.<br /><br />The higher diameter prop may drop your rpm, slightly, but will offer a greater holeshot and greater "holding" ability in turns.<br /><br />Again, make sure you can turn the rpms needed with a moderate load.

 

[coby-5]

Re: prop change help ! ! !

04 nitro Nx750....17 1/2 ft<br />04 90 hp mercury<br />WOT when trimed up high can go over 5500 ...maybe to 5700<br />at 5400 it does 52 mph on speedo<br />holeshot is fair but not great<br />stock prop is black max 12 3/4 X 21<br />replacement is express SS 13 1/4 X 21...from iboats prop page<br />hope this helps

 

[walleyehed]

Re: prop change help ! ! !

If RPM drops at all, you may need to move the engine up a hole, but over-all, I think you'll see a good improvement and you want to go no lower than 5500RPM if carbed , and 5800RPM if it's an Optimax.<br />What holes are in use now, as far as mounting holes??

 

[coby-5]

Re: prop change help ! ! !

right now the lowest holes are used<br />I measured and from shaft to bottom of boat is 8 inchs<br />worried about raising motor because prop has broken loose in turns at high speed!

 

[walleyehed]

Re: prop change help ! ! !

The bigger diameter prop will allow better bite in most cases and should help eliminate the blow-out.

 

[LubeDude]

Re: prop change help ! ! !

Originally posted by Bass Turd:<br /> worried about raising motor because prop has broken loose in turns at high speed!

Walleyehed is "The man about props", so he will get ya sorted out. Being an old bass boater myself, you will allways need to bump the trim dowm a bit on turns when trimmed out all the way, and walleyeheds right about the bigger diamiter prop helping your bite and having to maybe br raised at least another hole.