Bent prop --- on K Planes?!
07-22-2017, 07:53 AM
#1
Registered
Thread Starter
Bent prop --- on K Planes?!
Everyone, not even sure this was possible, but here goes.
Let me describe the equipment first.
2002 Cig TG TS
575 SCI
XR Drives, Bravo 1, 4 blade, 32P (labbed props), Kiekhaefer 380 Planes, Lathem external steering.
Backing out of my dock (at idle), probably 50' into my cove (deep water approx. 30') when I hear a "thunk". Continue to back out, shift into forward, no vibration at all.
Later when I pull boat back on my lift to access the damage I find a bent prop blade (starboard drive) and "nicks" on all other 3 remaining blades.
The marina who services my boat boat (LOTO, well respected, great reputation b4 anyone comments) calls and tells me that the the damage was due to the prop making contact with the starboard k plane. I was surprised because I did not even think this was possible. Mechanic said he is going to send me the photo showing point of contact. He further said that the drives were probably up as well as the planes. Now, after consulting a number of my friends who have a world of knowledge over me in all things mechanical (powerboat owners in particular who build their own engines) several said although not impossible to believe they found it highly improbable that this would have been the cause. Even the previous owner of the boat found it hard to believe.
Have not yet received the pics from the marina showing point of contact,but I will post as soon as I do.
I'm sending the prop to B Blades in WI (which I'm told are one of the best shops for this work). They quoted me $250 to repair after reviewing the pics I sent that they requested.
I guess what I'm asking the group is --- possible? plausible? If in fact this WAS the cause, can the steering be adjusted (a stop inserted) so that this could never happen again?
Thanks.
Let me describe the equipment first.
2002 Cig TG TS
575 SCI
XR Drives, Bravo 1, 4 blade, 32P (labbed props), Kiekhaefer 380 Planes, Lathem external steering.
Backing out of my dock (at idle), probably 50' into my cove (deep water approx. 30') when I hear a "thunk". Continue to back out, shift into forward, no vibration at all.
Later when I pull boat back on my lift to access the damage I find a bent prop blade (starboard drive) and "nicks" on all other 3 remaining blades.
The marina who services my boat boat (LOTO, well respected, great reputation b4 anyone comments) calls and tells me that the the damage was due to the prop making contact with the starboard k plane. I was surprised because I did not even think this was possible. Mechanic said he is going to send me the photo showing point of contact. He further said that the drives were probably up as well as the planes. Now, after consulting a number of my friends who have a world of knowledge over me in all things mechanical (powerboat owners in particular who build their own engines) several said although not impossible to believe they found it highly improbable that this would have been the cause. Even the previous owner of the boat found it hard to believe.
Have not yet received the pics from the marina showing point of contact,but I will post as soon as I do.
I'm sending the prop to B Blades in WI (which I'm told are one of the best shops for this work). They quoted me $250 to repair after reviewing the pics I sent that they requested.
I guess what I'm asking the group is --- possible? plausible? If in fact this WAS the cause, can the steering be adjusted (a stop inserted) so that this could never happen again?
Thanks.
Last edited by steve chalupka; 07-22-2017 at 04:05 PM.
07-22-2017, 10:06 AM
#3
Platinum Member
Platinum Member
iTrader: (6)
Are your drives on boxes ?? I have ITS 8 inch set back, and in the perfect scenario the prop will hit the k-plane, I found this out when bleeding the ps system after the engines went in and the drives went on while on the trailer.
07-22-2017, 10:21 AM
#5
VIP Member
I did it once.
I think you would only be able to do this with 380 planes, not with 280s.
I was negotiating some shallow water, and had just came off plane, having the tabs lowered to some point, because I knew I was coming off plane in shallow water. I did not pull the tabs back up, and did have the drives trimmed up (way further than they should be due to U-joint pinching), and upon putting the drives in reverse, and turning the wheel I clipped the trim tab. I knew what it was immediately. Fortunately, I was in reverse, so the prop nicked the tab with only the trailing edge (stock props, still thick) and no damage to prop, but took a nick out of the tab.
When I got home after that trip, I trimmed the corners off of my tabs; which is very, very common to do.
Your hydraulic systems are not "self aware" to know there will be interference, and do not have limiters accordingly.
I suspect you backed out with your drives too high, and didn't realize it. It's not a hard mistake to make. And now a fairly cheap lesson learned.
Just spray some Mercury Phantom Black on the tab for now, and come off season, pull them off and have the inner aft corners lopped off. It does not affect their performance in any fashion that you would notice. I took the measurements years back of how to cut them, but not sure I still have them. However, I know at least one person I gave those dimensions to still has the boat and can reproduce.
I think you would only be able to do this with 380 planes, not with 280s.
I was negotiating some shallow water, and had just came off plane, having the tabs lowered to some point, because I knew I was coming off plane in shallow water. I did not pull the tabs back up, and did have the drives trimmed up (way further than they should be due to U-joint pinching), and upon putting the drives in reverse, and turning the wheel I clipped the trim tab. I knew what it was immediately. Fortunately, I was in reverse, so the prop nicked the tab with only the trailing edge (stock props, still thick) and no damage to prop, but took a nick out of the tab.
When I got home after that trip, I trimmed the corners off of my tabs; which is very, very common to do.
Your hydraulic systems are not "self aware" to know there will be interference, and do not have limiters accordingly.
I suspect you backed out with your drives too high, and didn't realize it. It's not a hard mistake to make. And now a fairly cheap lesson learned.
Just spray some Mercury Phantom Black on the tab for now, and come off season, pull them off and have the inner aft corners lopped off. It does not affect their performance in any fashion that you would notice. I took the measurements years back of how to cut them, but not sure I still have them. However, I know at least one person I gave those dimensions to still has the boat and can reproduce.
07-22-2017, 10:33 AM
#6
Registered
Yes tabs hitting the props can happen.
07-22-2017, 03:24 PM
#8
Registered
We rerrig a 2007 Donzi 35 ZR, come with 496's and switch to 525's, no ITS or Extensión Boxes, the customer also switch the tabs bottom plate from 280s to 380s, with 15.25" diameter props hit the starboard trim tabs by 1/8", centerline are 34.5"
Gold Member
