Why is it on some of the bigger offshore boats with dual motors, they have props that spin in opposite directions? Is it to prevent the boat from ‘crab walking’ at wot?
Also, some of the bigger boats that have what looks like stacked props on the one motor? What’s going on there?
Might be some silly questions to some, but I am just curious whats going on there, thanks in advance fellas!
Fishing Nerd
“you win some, you lose some…but nothing beats getting some!”
Yes if both rotated in the same direction it would cause the boat to pull to one side. The boats with multiple props on the same shaft are actually counter rotating on different shafts. You see that on inboard cruisers. More power, less drag. Still can’t touch my 150s. 
26 Seahunt
Angler’s Dream
Yes, it’s to equalize steering torques so they are pushing, or pulling in opposite directions, which balance each other out. Twins should always counter rotate. I don’t know anything much about how trips are set up.
Capt. Larry Teuton
Swamp Worshiper
quote:
Also, some of the bigger boats that have what looks like stacked props on the one motor? What's going on there?
I think the only system I’ve seen that on is the Volvo Duo-prop drive, but it uses the same theory. Counter rotation = no torque. Although in my experience they are a mechanical nightmare and very expensive when they break. Not if, just when.
Capt. Larry Teuton
Swamp Worshiper
10 4! Thanks for the enlightenment!
Fishing Nerd
“you win some, you lose some…but nothing beats getting some!”
quote:If you don't maintain them... but isn't that true with anything. No problems with mine
Originally posted by Cracker Larryquote:
Also, some of the bigger boats that have what looks like stacked props on the one motor? What's going on there?
I think the only system I’ve seen that on is the Volvo Duo-prop drive, but it uses the same theory. Counter rotation = no torque. Although in my experience they are a mechanical nightmare and very expensive when they break. Not if, just when.
Capt. Larry Teuton
Swamp Worshiper
-Albemarle 248xf “Chella”
-Dolphin 18BC Pro
-Miscellaneous boats
“Praise the lord and pass the ammunition” -Howell Forgy
quote:
No problems with mine
Not yet? You got a good one 
I worked for a Volvo dealership with certified mechanics, factory trained in how to maintain them. I was the service manager. Nobody who had to work on them for a living would ever own one 
Capt. Larry Teuton
Swamp Worshiper
Ran an 01 hooked to a diesel for a long time and mine is an 03 hooked to a gas with no real problems. I know about the props sticking if not greased every year and the gimbal bearing. what other major problems have you seen? Would like to know if I need to do something different to my maintenance plan.
I have heard the composite unit can be a rough one to own.
-Albemarle 248xf “Chella”
-Dolphin 18BC Pro
-Miscellaneous boats
“Praise the lord and pass the ammunition” -Howell Forgy
quote:
Ran an 01 hooked to a diesel for a long time and mine is an 03 hooked to a gas with no real problems.
My information and opinion are out dated then, and positive changes may have been made that I’m not aware of with the Volvo duo-prop drive. I quit that job in 1991, and have not worked on one since then. Old age is talking. We hated for them to come into the shop, and we usually saw them again, and again… but that was then and not now
Albemarle makes a heck of a good boat. No doubt about that. Much better than most who get better reputation for some reason. And Volvo makes a dang good diesel engine too. But those early duo prop outdrives on them were a nightmare.
Personally I wouldn’t own a boat with an I/O of any kind, not even brand new. Straight inboard, or straight outboard for me.
Capt. Larry Teuton
Swamp Worshiper