silversupercoupe

No bellows yet.....hopefully, parts will arrive this week.

Wouldn't the postion of one prop relative to the other only effect the positon in rotation at which point blades would cross? In this case, maybe it makes sense not to have them cross directly under the skeg in order to minimize pressure pulses.

C_Spray

I agree with your logic, but don't understand why it would matter. If it was so important, I would have though that it would be easy to find information or bulletins on it, but I can't turn anything up using Google. I've owned Volvo DuoProps of various models for 14 years, and have never seen anything regarding clocking the props. I know that there are design aspects of Volvo props that Mercury cannot duplicate due to patent issues, so maybe that's why there is a Merc tech bulletin, and nothing on this from VP.

Can anyone post any sort of document, or will we have to go to Snopes.com to sort this out?
All I've found is anecdotal conversations, all relating to BlackHawk (surface-piercing) drives, where it would make sense that you would not want the props clocked in such a way that each prop had a blade striking the surface of the water at the same time. That would create some nasty vibrations, and the Blackhawk was abandonded for that reason anyway.

If both props are fully submerged, and the water flow around the skeg and lower gearcase is half decent (it had better be!), I can't see a reason for the orientation to matter. Besides, the leading edge of the rear DPX prop is so swept, it's hard to define where the front "edge" is.....

Looking at these press shots of the 600/DPX-A, it's hard for me to make a conclusive judgement. I'll have to see something in writing to be convinced it matters.

Magicfloat

Chuck,Merc bulletins don't have a search feature,but I do remember a drawing,but that was about 16 years ago.We did have a couple of situations where the props were not timed and performance suffered,so since it takes only an extra few seconds to time them when installing,why not time them? If the theory has no merit,then it wouldn't matter either wayIf I wasn't so busy trying to save my 382/600 sale over the octane issue,I bet I could find that drawing,but that is taking up most of my time right now

Knot 4 Me

My boat with a Bravo III loses performance if I do not clock the props properly. Simple as that.

Jeff

C_Spray

OK - I'll give it a whirl and keep you posted....

Knot 4 Me

It might not matter as much with Volvo's props as they are a bit different than Mercs. Still, it only takes an extra second or two to clock them so why not. I always set the forward (big) prop to where the anti-ventilation plate is directly between the 2 upper blades and then set the rear (small) prop with one blade straight up directly underneath the anti-ventilation plate.

techman

Confusion. Isn't it called the anti-ventilation plate? I believe cavitation is a different circumstance directly on the props due to pressure/heat/boiling point of water? The plate on top keeps the air or "ventilation" from entering into the prop stream.

Unless they are used interchangeably? Always was confused by that one.

Knot 4 Me

You are correct. However, I see so many people call the plate the cavitation plate that I used the term most seem to refer to it as. I corrected my other post. Thanks.

silversupercoupe

I may be opening up a whole new can of worms here....

....but has anyone had good or bad results after trying to make small repairs to their props themselves...i.e. with a file and/or sandpaper?

I have a few small nicks on the leading edges of my front and rear props that would probably smooth out nicely with some 400 grit paper. Do I risk throwing off the balance, or worse?

C_Spray

Small nicks should not be an issue. I've been at my props several times over the years with body hammers and dollies, files and sandpaper. (I used to boat around Philly, on the Delaware River/lumberyard...). It's not a bad idea to send them out if you've had to do a number of touchups, or had major damage. Some "PropScan" authorized shops will claim to check them at no charge, but somehow, they always manage to find something that needs "fixing".