professor_speed

I think what you are looking for what is the point of diminishing return? again still dependant on props/ prop height etc. look at what some hulls are doing with raised prop height and newer prop tech. Any of the new fast stuff has high prop heights and 5-6 blade props, the problem with standard bravo drive is depth and to get the prop up your center of gravity goes to crap if you just raise the engine, when possible its better to keep the engine low and shorten the drive. Look at what Steve Tripp and RPM 26 owners are doing. That is probably the best single I/O cat resources.

ray pampena

In my own experiences. . The pointy nose like imco etc only works out when the drive is right at the surface. The waters surface does not like the roundness of the bullet and you end up with blowout/slippage at hugher speed.. mid 80s and up.
running slightly deeper.. the other is true. The stock style rounded bullet type drive still has a very sharp leading edge above the bullet which is what is breaking the surface. When the deeper round bullet is under water.. it no longer airates the prop. The round style drive is shorter from front to back which creates lover drag even though it is not as pointy. The added length of the pointed lower cancels the effect of having the point when its deep.
the way I look at it is.. how high do you need to run your drive for your boats design.. setback.. water type being smooth or choppy. If it needs to be on the deeper side run stock lower.. if it needs to be at the surface run the pointed.
My information if from these examples of my experience. I ran an air entrapment hydrostream which needed no bowlift . A boat that doesnt need much bowlift help can be run higher. With the stock case it increased speed as I went higher until it kept blowing out in the mid 80s. Then.. I installed a cone and it slowed a bit at the same hight BUT once I went even higher I got 90s by going higher yet.

next is my 29 kryptonite. I have a stock bravo xr and run low/mid 90s. I bolted on a stock length imco lower and lost almost 2mph. Id need to raise it (shortie) to try and counteract that. But.. if I do.. I will be doing much more throttling in the rough

hope my experience helps you

Ray

Cobra100+

XR cases are faster than Imco size for size. The Imco is larger/ more robust that the XR. The smaller the case=faster it would be all things being equal otherwise.

the deep

Thank you Ray . What you have described is exactly what we are seeing but did not know the cause . In some of the vids of my cat at speed you can plainly see a splash pattern in the roost that indicates a surfacing prop . I don't yet have the power to get beyond 83mph gps but my friend does and is experiencing the wall at around 85mph . His is also a 25' single engine cat with a blown MR HP500 . Now we know what has to be done . Thank you again , this will be a tremendous help . Sam

ray pampena

Good luck with it Sam and post up your results! Thats a sweet boat

RaggedEdge

[QUOTE=the deep;4016979] . I don't yet have the power to get beyond 83mph gps but my friend does and is experiencing the wall at around 85mph



Been 94 with Bravos in this current boat, been just shy of 100 in the Velocity years back, have friends that have been well past 100 with Bravo boats, some with the standard lowers, some with cones etc. Doing so and not turning it into a grenade is more the trick than being able to get the number in the first place.

ray pampena

[QUOTE=RaggedEdge;4017149]ha! so true.

the deep

Hey Ray , I just measured to see where my prop shaft is in relation to the bottom . Prop shaft sits 1 5/8" below the lowest points on the sponsons . Do you think a -1" shorty is the way to go ? Maybe a prop that is meant to surface ?

professor_speed

The rpm 26s are I believe 2-2.5 above the center pod. Not sure where the center pod is on a warlock but food for thought.

the deep

This is the best pic I have of the drive in relation to the bottom . I have been told that the handling goes away on this hull with a -2" shorty but works well on a 25' Eliminator . I do believe my drive is set higher though .