Ran-Dom 32

you will never get on plane with 4 blades & being 3" above the sponson, I believe you are at the optimal position 1" above, all you need now is more HP

chromecat

I would try it with the 2" shorties.. and get some 5 blades... you may have to put in some 1" spacers in, but I would try it with the 3" and play with props... The nose cone on the shorties will help out too.

Don

phil_p999

Don, I think Randy is right about being too high. I can't spin my props over 5000 w/ 30p 4 blades, if I add a blade this will make things worse??

I'm going to leave the motors for the summer and possibly put some whipples on in the winter.

I have a serious case of "NFE"!

chromecat

you are right about adding a blade at that height, but if you raise the x up, you will need the blade to get the bite and ultimately you will speed up.

there are boats out there running with 3" above and they are using 5 blades to make it work. I would not recommend that setting if you are running high hp... because the boat will get too loose, but with 500's you will optimize your speed by going that high and getting the props to work with you there......

good luck
Don

phil_p999

thanks for the input Don.


When are you going to get back into a cat?

tssteph

The reason Don is saying to try shorties is because of the boxes. Most of us do not have have boxes and even or a little above is about perfect with that config.

tssteph

i personally picked up 9 mph with -2 shorties with no boxes and absolutly no other changes. With that being said my boat really frees up around 95 mph which is where I was stuck prior to the shorties. Mine is a 98 so is probably similar in weight to yours.

Also 95 mph at 5000 rpm with 30 pitch props and 1.50 drives would be zero slip. This is not likely. Some number somewhere must be off.

ROTAX454

Phil, The picture of your outdrive leaves me with the idea that those ext boxes are stellings. If so, they have a limited vertical movement/adjustment. In general terms (jump in here guys if my info needs correcting) the IMCO and Stelling in the neutral position will give you a 1" drop of your prop shaft vs. having the Bravo transom assembly mounted directly to the transom.

So, what is the common X dimension of an AO with a Bravo 1 with a standard lower? I am trying to figure out the -1" dimension with your standard lower. Did AO have a factory higher outdrive transom cutouts? Or, they are Stellings positioned in the upper location?

If you do stick with the standard lowers, (as others have suggested) you will need to install a nose cone. My recommendation is the Hydromotive unit.

ROTAX454

I was also crunching the numbers and the 30P x 5000rpm didn't get it to 95 mph (with a common slip % thrown in). My boat using a standard Bravo 1 28P prop at exactly 5000 read 78.9mph on the Garmin.

tssteph

Normal is roughly 2 down. His extension boxes are probably in the 3 up position giving it 1 above.