I recently bought a 1992 H28. During sea trials, I noticed that there was more vibration and movement in the prop shaft than I expected. I know that the cutlass bearing needs to be replaced but that can't account for all the vibration. Is it possible that the previous owner got a mooring line or lobster trap wrapped around the prop and bent the prop and/or the shaft? If the shaft is bent, how can I tell? If the prop is out of balance or bent, how can I tell? Can the vibration be caused primarily by the alignment of the engine? Any advice about correcting the situation so I can motor "vibration free"? Thanks.
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Quality, didn't you haul the boat and inspect
the underside prior to purchase? It's a must in order to find the problem you are having. With the boat out of the water, the shaft is turned. Look for any sign of a bow. If the prop looks good and true, well, that's all you can do without pulling it and sending it to a shop. During the pre-purchase haul out your surveyor looks for stuff like structural damage and electrolysis damage. If you were planning to pay a fair market price, it's important.
the underside prior to purchase? It's a must in order to find the problem you are having. With the boat out of the water, the shaft is turned. Look for any sign of a bow. If the prop looks good and true, well, that's all you can do without pulling it and sending it to a shop. During the pre-purchase haul out your surveyor looks for stuff like structural damage and electrolysis damage. If you were planning to pay a fair market price, it's important.
could be a number of problems
the vibration could be caused by fouled prop, by barnacles, growth, and yes a net or line caught on the shaft or prop. My engine vibrated excessively when the exhaust elbow was clogged. Bottom line the surveyor should be able to tell you what it is. (if you can't figure it out for yourself)
the vibration could be caused by fouled prop, by barnacles, growth, and yes a net or line caught on the shaft or prop. My engine vibrated excessively when the exhaust elbow was clogged. Bottom line the surveyor should be able to tell you what it is. (if you can't figure it out for yourself)
vibration
can only be caused by 4 things: bad prop, bad bearing, bent shaft, or out of alignment. Or any combination of these together.
can only be caused by 4 things: bad prop, bad bearing, bent shaft, or out of alignment. Or any combination of these together.
Hauling for a Survey was a Must
I did have the boat hauled and a thorough survey conducted. Rotating the shaft didn't reveal anything out of the ordinary. Of course at higher RPMs (say 2000) even a slight bend that is inperceptable by turning the shaft will cause a fair amount of vibration. I didn't do more than visually look at the prop. It also seemed OK -- and again even a slight misalignment will shake everything. I knew that the cutlass bearing needed replacing but I don't think that alone would cause the vibrations (or would it?) I plan to pull the shaft and prop and have the local yard do a better check. While the shaft is out, I'll replace the cutlass bearing, swap the plastic stuffing box for a bronze one, replace the hose connecting the stuffing box to the hull, and do a rough (out of water) alignment. Once I go back in the water next spring, I'll do the final engine alignment. I just hope I don't have to fork out $500 for a new prop and another $$$ for a new shaft. what do you think about having a bent shaft or prop "fixed"?
I did have the boat hauled and a thorough survey conducted. Rotating the shaft didn't reveal anything out of the ordinary. Of course at higher RPMs (say 2000) even a slight bend that is inperceptable by turning the shaft will cause a fair amount of vibration. I didn't do more than visually look at the prop. It also seemed OK -- and again even a slight misalignment will shake everything. I knew that the cutlass bearing needed replacing but I don't think that alone would cause the vibrations (or would it?) I plan to pull the shaft and prop and have the local yard do a better check. While the shaft is out, I'll replace the cutlass bearing, swap the plastic stuffing box for a bronze one, replace the hose connecting the stuffing box to the hull, and do a rough (out of water) alignment. Once I go back in the water next spring, I'll do the final engine alignment. I just hope I don't have to fork out $500 for a new prop and another $$$ for a new shaft. what do you think about having a bent shaft or prop "fixed"?
Any good shop can do it.
don't let somebody in Tim buck too (I know, I can't spell it and I don't care
) sell you new stuff if you don't want it. It's a matter of planning to keep your options open. If it looked good when you bought it, odds are even goodder it's fixable. Not sure about the cutlass being the problem but when you replace it have the shaft and prop checked at the same time. You won't need it but good luck anyway.
don't let somebody in Tim buck too (I know, I can't spell it and I don't care
) sell you new stuff if you don't want it. It's a matter of planning to keep your options open. If it looked good when you bought it, odds are even goodder it's fixable. Not sure about the cutlass being the problem but when you replace it have the shaft and prop checked at the same time. You won't need it but good luck anyway.The cutlass bearing is a clue
This may have been a problem for a while. Bent shaft is possible. So is a bent prop. Run over a crab pot, dock line or painter and you could do that. The line might work its way into the cutlass bearing and tear it up a little too. Look for any indications you can see ie: worn paint, scratches and dings, corrosion too. To check the shaft, get a dial indicator and clamp its mounting bracket onto something solid (skeg rudder, etc). Hold the shaft end solid at the prop end or at else tighten the cutlass bearing using something (small wooden wedges?) to remove any play in the mounting. Turn the shaft slowly by hand and look for some out of round indication. Anything more than about ten thousandths of an inch is a concern. Bent shafts can be straightened - in or out of the boat. Find someone competent to do it! You didn't say anything specific about the prop. Two blade props vibrate more - in my experience. Alignment could be checked easily but you did not say if you did that. While you are at it, ALWAYS check the elbow. That will tell you something about the engine too. Vibration free motoring? - I doubt it but your teeth shouldn't rattle.
This may have been a problem for a while. Bent shaft is possible. So is a bent prop. Run over a crab pot, dock line or painter and you could do that. The line might work its way into the cutlass bearing and tear it up a little too. Look for any indications you can see ie: worn paint, scratches and dings, corrosion too. To check the shaft, get a dial indicator and clamp its mounting bracket onto something solid (skeg rudder, etc). Hold the shaft end solid at the prop end or at else tighten the cutlass bearing using something (small wooden wedges?) to remove any play in the mounting. Turn the shaft slowly by hand and look for some out of round indication. Anything more than about ten thousandths of an inch is a concern. Bent shafts can be straightened - in or out of the boat. Find someone competent to do it! You didn't say anything specific about the prop. Two blade props vibrate more - in my experience. Alignment could be checked easily but you did not say if you did that. While you are at it, ALWAYS check the elbow. That will tell you something about the engine too. Vibration free motoring? - I doubt it but your teeth shouldn't rattle.
Exhaust elbow is on the back of the engine
It is the cast iron fitting where cooling water is injected into the exhaust system. It tends to get filled with soot and rust over time especially if the engine is not run hard enough and long enough to get it hot. I do not know your engine but mine is attached with 4 bolts into the manifold and a hose clamp each on the water injection line and the exhaust hose. Use care when you remove it and you won't even need a new gasket. Pull the hoses, loosen the bolts, give it a twist to loosen the gasket, remove the bolts holding it and look inside. Chisel out the soot with a screwdriver and look for cracks. If it is ok, put it back. If not replace it. Shop around prices vary a lot - mine was quoted at $400+ to $86 locally If it is filled with soot, that may be your main problem. This is a good annual maintenance item but few people do it. You also can check the archives.
It is the cast iron fitting where cooling water is injected into the exhaust system. It tends to get filled with soot and rust over time especially if the engine is not run hard enough and long enough to get it hot. I do not know your engine but mine is attached with 4 bolts into the manifold and a hose clamp each on the water injection line and the exhaust hose. Use care when you remove it and you won't even need a new gasket. Pull the hoses, loosen the bolts, give it a twist to loosen the gasket, remove the bolts holding it and look inside. Chisel out the soot with a screwdriver and look for cracks. If it is ok, put it back. If not replace it. Shop around prices vary a lot - mine was quoted at $400+ to $86 locally If it is filled with soot, that may be your main problem. This is a good annual maintenance item but few people do it. You also can check the archives.
Your prop shop knows which prop!
QT: If you want to change your prop, you need to check with a reliable Prop Shop. They will fit the proper prop to your vessel. DO NOT DEPEND ON HEAR-SAY!
QT: If you want to change your prop, you need to check with a reliable Prop Shop. They will fit the proper prop to your vessel. DO NOT DEPEND ON HEAR-SAY!
Just been through it all
Don't know what happened or when but boat developed an intermittant minor grinding,groaning and vibration in aft section. I had a diver check cutlass bearing and nothing was obvious like looseness and I then had an engine alignment and it helped a little. Cutlass Bearing then totally failed while transiting from Ft. lauderdale to Miami with resultant extreme shaking and noise. Shutdown engine and got Tow to Norseman Marine where they found that shaft was bent and prop needed reconditioning. I also had bottom done and a dripless stufing box installed. Shaft runs straight now and all is fine but wish the 18 HP Yannmar did bounce so much on its rubber mounts. Jim
Don't know what happened or when but boat developed an intermittant minor grinding,groaning and vibration in aft section. I had a diver check cutlass bearing and nothing was obvious like looseness and I then had an engine alignment and it helped a little. Cutlass Bearing then totally failed while transiting from Ft. lauderdale to Miami with resultant extreme shaking and noise. Shutdown engine and got Tow to Norseman Marine where they found that shaft was bent and prop needed reconditioning. I also had bottom done and a dripless stufing box installed. Shaft runs straight now and all is fine but wish the 18 HP Yannmar did bounce so much on its rubber mounts. Jim
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