Great Moments in Cat History
01-03-2012 | 07:06 PM
#701
Thread Starter
Allergic to Nonsense
Joined: Aug 2001
Posts: 5,007
Likes: 21
From: Granite Quarry, NC
Great thread. Never saw it until this year and have been trying to read the whole thing but never quite get there. I have read posts 1 - 100 about 10 times though while trying to get through it.
The prop rotation information was particularly enlightening. I never considered the torque factor and feel lucky I have never had an incident due to my rotation (in). I plan on reversing my rotation this off season.
There is another variable I would like to get T2X's take on regarding prop rotation. Assume a 36 Skater with #6's.
I would think that the Port side prop blades when turning out would be entering the water above the horizontal centerline due to the fact that the hull angle would deflect the water such that it is higher on the left side of the prop and lower on the right side of the prop. It seems this would be true at least at slow and medium speeds when there is still a reasonable amount of the hull - at the transom - in the water. Over 120, I'm guessing it doesn't make much difference as there isn't much hull in the water even at the transom at high speed.
If the prop enters the water above the centerline when turning out, you would think this would result in additional transom lift. Conversely, when turning in, the prop would (theoretically) enter the water below the centerline, resulting in less transom lift. Perhaps this would require less energy and result in a few extra mph, as I have experienced when I changed from an "outie to an inee".
I have no idea if this is accurate. This is a question, not a statement of fact. I would like to get T2X's take on this as he seems most qualified to confirm or debunk the idea.
The prop rotation information was particularly enlightening. I never considered the torque factor and feel lucky I have never had an incident due to my rotation (in). I plan on reversing my rotation this off season.
There is another variable I would like to get T2X's take on regarding prop rotation. Assume a 36 Skater with #6's.
I would think that the Port side prop blades when turning out would be entering the water above the horizontal centerline due to the fact that the hull angle would deflect the water such that it is higher on the left side of the prop and lower on the right side of the prop. It seems this would be true at least at slow and medium speeds when there is still a reasonable amount of the hull - at the transom - in the water. Over 120, I'm guessing it doesn't make much difference as there isn't much hull in the water even at the transom at high speed.
If the prop enters the water above the centerline when turning out, you would think this would result in additional transom lift. Conversely, when turning in, the prop would (theoretically) enter the water below the centerline, resulting in less transom lift. Perhaps this would require less energy and result in a few extra mph, as I have experienced when I changed from an "outie to an inee".
I have no idea if this is accurate. This is a question, not a statement of fact. I would like to get T2X's take on this as he seems most qualified to confirm or debunk the idea.
01-04-2012 | 08:33 AM
#704
Thread Starter
Allergic to Nonsense
Joined: Aug 2001
Posts: 5,007
Likes: 21
From: Granite Quarry, NC
01-04-2012 | 07:26 PM
#707
Registered
Joined: Mar 2002
Posts: 2,142
Likes: 3
From: Miami Beach
T2x is spinning in always bad? I have a center console with twin diesels with bravo x drives. I don't gain any speed spinning in but I do get a 10% increase in fuel economy. The boat tops out at 55 but my cruising speeds are 30-45 mph usually 38.
I do think my boat needs more bow lift I installed 1.5" spacers and that helped, I'm running bravo 4 blades now but also have Maximus 5 blades that give me more lift but they seem hard on the drives. Curious as to your opinion.
I do think my boat needs more bow lift I installed 1.5" spacers and that helped, I'm running bravo 4 blades now but also have Maximus 5 blades that give me more lift but they seem hard on the drives. Curious as to your opinion.
01-05-2012 | 12:33 AM
#708
Banned
Joined: Feb 2005
Posts: 9,373
Likes: 1
From: Arlington Tx
01-05-2012 | 06:43 AM
#709
Thread Starter
Allergic to Nonsense
Joined: Aug 2001
Posts: 5,007
Likes: 21
From: Granite Quarry, NC
T2x is spinning in always bad? I have a center console with twin diesels with bravo x drives. I don't gain any speed spinning in but I do get a 10% increase in fuel economy. The boat tops out at 55 but my cruising speeds are 30-45 mph usually 38.
I do think my boat needs more bow lift I installed 1.5" spacers and that helped, I'm running bravo 4 blades now but also have Maximus 5 blades that give me more lift but they seem hard on the drives. Curious as to your opinion.
I do think my boat needs more bow lift I installed 1.5" spacers and that helped, I'm running bravo 4 blades now but also have Maximus 5 blades that give me more lift but they seem hard on the drives. Curious as to your opinion.
Wow! I have no idea why prop rotation in that speed range would have so dramatic an effect on fuel economy....unless you have something causing cavitation from the hull or drives. Is there a hook in the bottom? Put a straight edge (at least 10 feet long) on it and check the entire running surface. Also check the centerline measurements on your drives.
