Rudder length and location

[12ftgso480]

Trying to finish up a project boat. This hull had a small block direct drive. We have moved the rigging forward and raised the cage close to a foot to allow for bigger blade and added a gearbox. I just noticed that my rudders are now off center from my prop and need modified to bolt back on. The original rudders are 4' and I think I can build a pedestal for them. Does anyone know the importance of switching to a bigger prop on same boat without switching rudders ? The bottom of prop is really close to flush with the transom. If they are not quite perfectly centered up and down will it cause issues/porpoising ect ?

 

[Arbuckleoutdoors87]

Trying to finish up a project boat. This hull had a small block direct drive. We have moved the rigging forward and raised the cage close to a foot to allow for bigger blade and added a gearbox. I just noticed that my rudders are now off center from my prop and need modified to bolt back on. The original rudders are 4' and I think I can build a pedestal for them. Does anyone know the importance of switching to a bigger prop on same boat without switching rudders ? The bottom of prop is really close to flush with the transom. If they are not quite perfectly centered up and down will it cause issues/porpoising ect ?

I personally like my rudders low, less lean more slide when turning.

 

[John Fenner]

Rework top, plumb center to boat "leveled" re tab top, build hoop and tabs for bottom, plumb bob is your friend here, 22" apart 11" from center each side, only want about 9" from prop give or take.
You may find later that those 48" rudders are not quite enough, may need to go 60", IMHO.

 

[Coastslider]

Prop can be 5” or so below transom height. Plenty of car motor boats out there with 48” rudders and 82” props. Sounds like the original motor stand was a tad bit to high

 

[12ftgso480]

Gotter did. Thanks guys