Commuter Boats
Commuter Boats
- Joined
- Oct 28, 2006
- Messages
- 177
- Reaction score
- 12
- Location
- Southeast Alaska
Good morning folks, I've got some questions about shaft bearing temperatures.
Shaft alignment is something that I don't normally get called for in less there's somethings unusual or somebody else has made a significant mess, two external cutlasses / struts on a twin-engine yacht, vessel lengthening, etc.
I have a great client with a 40-year-old commercial fishing boat who undertakes a big job every other year on his vessel with the intent to rebuild better than new. A few years ago I was involved in replacing the stern bearing while another mechanic replaced shafting and realigned the engine/ shaft bearings. Last fall my client hauled out so that I could replace the little bulkhead that the shaft gland was mounted on, I chipped out concrete, renewed the shaft tube and replaced the bulkhead. Got everything hooked back up so the client could launch the boat and returned to his slip where I demoed most of the fishhold and shaft alley, built new support beams for the intermediate bearings and other associated work. Works completed and on sea trials the aft bearing was running at about 112° and the forward one was running at closer to 130°. I've mucked around with it some and presently have the aft bearing at 116° and the forward bearing at 112° when the boat is run hard ( temperatures are lower at normal cruise ). The gland is staying within a couple degrees of the ocean temperature with only a minimal amount of water passing the packing. The shafting is about 22 feet long, 2 inch stainless with about 5 feet between the transmission and the first bearing, 5 feet between the two bearings, and about 4 feet between the aft bearing and the cutlass with a shaft coupling close to the aft bearing. There's about 6 feet between the gland and the stern bearing.
I'm not knowledgeable enough to know what the best case scenario might be as far as temperatures and how much effort I should put into improving the situation.
Recommendations and past experience would be appreciated, thanks
Gerald
pictures to follow in another post
b
Shaft alignment is something that I don't normally get called for in less there's somethings unusual or somebody else has made a significant mess, two external cutlasses / struts on a twin-engine yacht, vessel lengthening, etc.
I have a great client with a 40-year-old commercial fishing boat who undertakes a big job every other year on his vessel with the intent to rebuild better than new. A few years ago I was involved in replacing the stern bearing while another mechanic replaced shafting and realigned the engine/ shaft bearings. Last fall my client hauled out so that I could replace the little bulkhead that the shaft gland was mounted on, I chipped out concrete, renewed the shaft tube and replaced the bulkhead. Got everything hooked back up so the client could launch the boat and returned to his slip where I demoed most of the fishhold and shaft alley, built new support beams for the intermediate bearings and other associated work. Works completed and on sea trials the aft bearing was running at about 112° and the forward one was running at closer to 130°. I've mucked around with it some and presently have the aft bearing at 116° and the forward bearing at 112° when the boat is run hard ( temperatures are lower at normal cruise ). The gland is staying within a couple degrees of the ocean temperature with only a minimal amount of water passing the packing. The shafting is about 22 feet long, 2 inch stainless with about 5 feet between the transmission and the first bearing, 5 feet between the two bearings, and about 4 feet between the aft bearing and the cutlass with a shaft coupling close to the aft bearing. There's about 6 feet between the gland and the stern bearing.
I'm not knowledgeable enough to know what the best case scenario might be as far as temperatures and how much effort I should put into improving the situation.
Recommendations and past experience would be appreciated, thanks
Gerald
pictures to follow in another post




