setting prop back on prop shaft

[daytrader]

What does setting the prop back a little on the prop shaft accomplish? Is it hard on the shaft bearings? Ive seen it done on drag boats, the prop set back with a spacer or washers.

[rock]

As the water hits the front of the lower it parts to go around lower. This gives the water a hair more time to return to the surface of the lower unit plus the water will be a bit cleaner. This tends to increase blow-out speed.

Rock

[daytrader]

So I would assume that the prop gets a little more bite being back in "cleaner" water.

[rock]

I've tried it and not noticed any difference but maybe some have. Most times I seen it another thrust washer was used which seemed to me could easilly throw things off balance. I made a spacer that fit correctly on the shaft to avoid the issue. It has to put a bit more side load on the prop shaft and wear the seals a bit more. Anything for a tenth of a second.

Rock

[davemvegas]

I am guessing the only reason to run a thicker washer. Would be to create a gap for exhaust to ventilate prop.

[Ted Stryker]

It doesn’t let more exhaust into the blade, and I have noticed a fuzz more bow lift of a hot v6 and light vee bottom.

[daytrader]

It doesn’t let more exhaust into the blade, and I have noticed a fuzz more bow lift of a hot v6 and light vee bottom. I agree, mainly because most of these boats have relieved exhaust systems

[rock]

I have noticed a fuzz more bow lift of a hot v6 and light vee bottom.

Which makes perfect sense. Small gain in leverage.

Rock

[crazy horse]

I still have a 14X30 two blade from Michigan wheel that I did that with. This prop was made for me when I first had my viper. It is a solid hub and it has the smallest hub I've ever ran. I just checked it and it is only 3 3/8 long by 1 1/4 dia. I made spacers for it and play with it using lip stik on the blades. My boat is real light and I could feel the change when I ran back on the shaft. When I bought my first VC cleaver I never looked back.

[daytrader]

I still have a 14X30 two blade from Michigan wheel that I did that with. This prop was made for me when I first had my viper. It is a solid hub and it has the smallest hub I've ever ran. I just checked it and it is only 3 3/8 long by 1 1/4 dia. I made spacers for it and play with it using lip stik on the blades. My boat is real light and I could feel the change when I ran back on the shaft. When I bought my first VC cleaver I never looked back. What changes did u feel?

[crazy horse]

Way back then I had read a couple of things about fine tuning props and want to screw with it. The bow seemed a little lighter and the steering felt a little tighter or stiffer, Maybe? I remember using lip stik on the 14 in. dia prop and was kinda surprised how little of those prop blades would run in clear water. Moving the prop back chaged that area a little. I'm pretty sure messing with it didn't help my gearcase back then. That 14X30 with a bunch of cupping would rattle that whole boat.

[99fxst99]

I would think it would be more susceptible to breaking the prop shaft with the prop sitting further back

[daytrader]

[QUOTE=crazy horse;3066479]Way back then I had read a couple of things about fine tuning props and want to screw with it. The bow seemed a little lighter and the steering felt a little tighter or stiffer, Maybe? I remember using lip stik on the 14 in. dia prop and was kinda surprised how little of those prop blades would run in clear water. Moving the prop back chaged that area a little. I'm pretty sure messing with it didn't help my gearcase back then. That 14X30 with a bunch of cupping would rattle that whole boat.[/QUOTE How far back would u move the prop, roughly? Also, always loved your boat,and I love those old 2 blades. My first hydrostream was a viper.

[Ted Stryker]

I would think it would be more susceptible to breaking the prop shaft with the prop sitting further back

Most likely has a degree of negative effect or fatigue if ran hard or for extended time. If a prop has any rake or natural “pull down” when only the bottom half of the prop is in the bite, then yes I think it’s the same effect as reaching your hand farther out on a breaker bar.

[Instigator]

Basically like adding rake.
In theory.

I tried it on my 543 lb, 101 mph Vector and saw nothing.

[Ted Stryker]

Basically like adding rake.
In theory.

I tried it on my 543 lb, 101 mph Vector and saw nothing.

My rig at the time was a 1993 17cc Bullet comp layup est.625lbs, 6” setback with a heavily cut steel 2.5. Prop was a Yamaha drag on the short, and lake riding was a worked 24pitch chopper 2.

[crazy horse]

Well,I can't remember how far back I try to run that two blade but it was far enough to mount a 1.125 blowout ring on the case. I still have the old ring hanging in the shop. I guess I don't get rid of anything around here. Seems like that what I was looking at was if you could reduce the blowout threat with those two blade wheels back in the early 70's.