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Changing shaft angle?


DarkSide

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Just a curiosity here. First I am not sure if this is even feasible. Given the following. Malibu has shallow prop angle I calculated 10.4 degrees. This allows a 45" shaft to have 8.25" of hull clearance. Thus it only accommodates a 15" prop.

If a person was to put a small spacer between the hull and strut. Say .375 inch, this would create an extra 1/2" of hull clearance allowing a person to now use a 16" prop. This would change the prop angle by 0.6 degrees netting a new angle of 11.0. You could also increase spacer to 3/4 or so and create enough clearance to accommodate a 17" prop. This changes prop shaft angle to 11.6 degrees. A difference of 1.2 degrees from baseline

For those who like to run heavier weights and the new boats with taller trannies this could help.

I am not a mechanic, I just am curious if this would be a feasible option. Also what would the consequences be?

Edited by DarkSide
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Darkside - don't you have the LSA? I've run a ton of weight, wedge, and 10 people and not had any issues. My tranny is 1.25:1. What prop are you running?

I will say you do need bow weight if you're running an extra 2800lbs and all those people though.

PS I'm in MN...so altitude is not an issue.

Edited by tjklein
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I am not having issues, just curious. The 17 x 17 seams to be the standard for really heavy boats. M235/G's

Ahopkins, I wouldn't change v drive to engine connection. Just the angle between prop and vdrive, thus increasing the spacing allowing for a larger diameter prop. The smaller props seam to slip more.

This is really just a hypothetical. When I started searching for a prop this summer, oj really wanted a greater diameter but that was not an option. So I guess the question is what is the tolerance of vdrive shaft angle. I wouldn't think 1 degree would cause an issue. But I AM NOT A MECHANIC.

TJ: I typically run Full MLS 800 in the bow and 1300 in each corner, plus crew and a couple clicks of wedge. Yes LSA, OJ 15 x 15.5 prop

Edited by DarkSide
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The shaft has to stay in its line since it is coupled to the v drive or transmission. The shaft log has to have proper clearence, then the strut sets the angle within the logs opening, then the engine/tranny/vdrive has to be angled at that same angle so the couplers will seat square on each other otherwise it will want to gap and be put of alignment and cause stress and breakage. I bet it could be done but there are more points to consider than just shimming the strut to create a different angle.

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The steeper your angle to accommodate a larger dia prop the more you become inefficient due your vector of downward thrust.... Assuming you could solve engine/tranny alignment issues.

So as you reduce prop slip with a bigger dia prop... You trade in a more inefficient thrust direction.

17" prop boats need to be engineered like that from the beginning.

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I think I understand now why this will not work. I was just curious. Again flawed thinking. But when you lift a truck, the engine/tranny, does not move, the drive shaft angle changes a little. I suspected there was a reason no one had tried this.

Thank you for the answers, it is appreciated.

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I think I understand now why this will not work. I was just curious. Again flawed thinking. But when you lift a truck, the engine/tranny, does not move, the drive shaft angle changes a little. I suspected there was a reason no one had tried this.

Thank you for the answers, it is appreciated.

Different styles of connections.

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I think I understand now why this will not work. I was just curious. Again flawed thinking. But when you lift a truck, the engine/tranny, does not move, the drive shaft angle changes a little. I suspected there was a reason no one had tried this.

Thank you for the answers, it is appreciated.

The driveshaft is designed to accommodate up and down travel, and the subsequent changes in angle. I'm pretty sure teh V-drive system is rigidly mounted.

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On our boats everything is a rigid connection with fixed angles. On cars/trucks you have universal joints or CV joints that are designed for a range of angular Mia-alignment.

In reality to swing a larger prop with the existing V-drive you could lower the front of the engine (this is at the back of the boat near the transom) but the shaft log, the opening for the prop shaft and the strut would all have to be modified or changed. At this point you might as well start looking at a different boat that will generate the wake/wave you want in an "as delivered" configuration with maybe additional ballast. But then here we go again with the slippery slope of more weight requiring more prop and so on.

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if you did not want to change the alignment angles, you would need to lengthen the shaft which would give more clearance. but then the strut would need moved aft as well and so would the rudder so the lengthened prop would not hit it...

so as someone else previously posted, a NEW and DIFFERENT boat is a better solution than to try and re-engineer a boat after the fact... :whistle:

just my .02

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