375stinger

i had a hard tiem gettin an answer for thsi in the tech section.. where shold the propshaft be in relation to the bottom of the hull in triple engines bravo nose cone cigarette? thanks

Comanche3Six

Craig Barrie might be the one to answer that question.

bbladesprops

Without trying to sound condescending, it should be wherever the boats personality wants it to be. It could be between 5'' below to 2" above. Most likely the answer will be some place between.

How does the boat perform now? What characteristics are bad?

375stinger

bad porpoise when raising drives slightly at about 70. puttin new engines in withitn next few weeks. (burned up cylinders in all of em) triple stock bravo 600 horse 625 torque. showers, nose cones. drive placing is same as from factory. boat in theory should run upper 80s close to 90. 4 blade 26 pitch hydro inside (right hand rotation) and two 25 pitch hydros outside. I understand that it should be wherever the boat performs best at, but i dont want to buy 6 thousand dollars worth of equipment for somtthing such as extension boxes, and find out that it handles worse. hope to go down thsi weekend to get some measurements etc. thanks

bbladesprops

The more information you can give us, the better we will be able to help. Besides the X dimension, we need rpm/speed numbers at WOT and any others you have.

We may be able to help some of the porpoising with propellers, but drive depth may come into play too. I'm assuming the outer props turn out not in?

May be best to get new numbers once the engines are back in place.

Keep us posted.

375stinger

hard to say cuse the engines only had 5/16 fuel linesbefore so were only makin abuot 400 something hp. and with the same props maxed at 4800 rpms and got about 70 with drives in neutral. if we raised the drives at all it would porpoise horribly. i have never payed attention to which way the outer props turn (we have been restoring it over a year and have only ran it 6 hours). how could which way the props turn affect how the boat handles, speed etc? just talked to the engine builder, and it should be a few weeks until the engines in and able to run, but not sure how soon it will get warm around here. i can get the measurements very soon thou. what kind of propellers would be better to reduce porpoising? i have heard that 3 blades cause a lot less porpoising than 4 bladdes. hope to get more info soon. thanks

zum.offshore.Malta

Hi guys ... i would like to know how to calculate the X dimension myself or if its posible i would like to ask someone out there if they are ready to help me out with my query i got a 30 footer deep vee offshore with 22 degrees deadrise and with a maximum beam of 8 feet ... i will install a 525 mercruiser with a bravo 1 or more likely an XR drive ... ! ! ! ! but do not know the hieght of the propshaft what it should be from the keel. the hull has no notched transom and it has a constant of 240..... for a lot of u out there its a simple question but not for me ..thanks ! ! ! actually i was wondering to build the next boat with a notched transom this time... again with a single mercruiser 525 and XR drive.... knowing that a notched transom helps to raise the drive s height....but have no clue what should b the height nor the length of the notched transom to work properly.............. ! ! ! any ideas ???????????

throttleup

Because of different lowers and spacers I prefer to reference prop shaft distance in relation to the bottom of the hull.

For a boat like yours the drive will not be able to be raised too high. If you don't have an extension box or a notch a good place to start would be to mount the prop shaft 3 1/2" below the bottom of the hull. If you were to mount it a little higher than that it would be OK. You could always use a spacer to lower the prop shaft deeper, if necessary.

Matt

bbladesprops

Spacing down is always a option, bringing the drive up can require a much larger amount of work. Spacers are available in 1/2" increments to 3". A hull like yours would typically have a low prop shaft depth (no notch will amplify this even more). It may be as low as 5.5" below the lowest point of the keel.. I agree it is smart to start a little higher. and space it down as needed.