I have a single engine Donzi 26 with 2" high X dimension. If i fit an extension box, could i go up 3" or should i run neutral? Would a bravo prop cope, or was thinking of a maximus!

Don't go to the Maximus.

Your current attitude (of the boat I mean, lol) will determine whether you can go up. On these boats, all though we want to go up, depth is ussually the best route.

Have purchased stand-off box which has the facility to be fitted an inch either side of current X dimension. Are you suggesting I fit it an inch lower than I am currently running? Reading the suitability of the Maximus prop - I thought they were designed for stepped hulls and to improve prop efficiency. Thank you for your thoughts on this issue.

Cheers

If you go up, the added diameter and blade area of the Max will be a help.

I may have spoken too quickly. I don't know your current performance numbers.

Lately, higher X dimensions have caused efficiency issues on these boats however. What type of numbers are you currently running and with which propeller selection?

Am running a stock 30" Bravo prop on an XR with 1.50 ratio. Drive height is 2" high. I have a modified 502 fitted with a M3 prochager. Never really had the throttles to the stops long enough to play with trim etc, but she runs up to 5400 - my max rpm showing 88 on gps. At that point I chicken out, as she starts what i think, to chine walk! I do feel she likes to run a lot of trim (up to 7), but need to trim back into 3 if wanting to do high speeds. This happened at 78, then I fitted big tabs and this seemed to help. So i thought if i fit an extension and even bigger tabs and a change of gear ratio to 1.26 incase it is prop torque.................... who knows ?!!? Your thoughts would be appreciated again

I wonder if your prop surfacing is causing some of your instability?

Hi Bill
Yes thats my thoughts ! Have purchased an extension box
which can mount 1" either side of exsiting gimbal position
and dont know which way to go !!Read another thread saying
moving back 12" drive goes down 3" !! Also have got 1.26
lower gear set and nose cone to fit then will swing smaller diameter prop possibly 5 blades ? What yoju rekon
Trevor

I would start with the Five blade.

I am dying to know if the ext box helps since I have mine all torn down now.

A nose cone is always a consideration since you are in the speed range where they start to help. That is not a big gamble there.

As for the height thing, hopefully someone more versed than me will chime in.

Are you going to be testing some more soon?

Bill