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Hi
I have a trapper 500, about the same as a mark 3 I think, Late last season I noticed a rumble noise coming from the area of the prop when motoring. I assumed it was probably fouling on the prop and kept the revs low. I have just relaunched following 8 weeks of winter maintenance which included cleaning up the prop and shaft and applying the Seajet 'pellor clean' antifouling.
I'm disappointed to find that the rumble is still there in forward and reverse. I had the cutlass bearing, prop shaft and engine mounts replaced 18 months ago. The engine is a volvo 2002 18hp with a 13 x 9 prop, the tip clearance is only about 3/4". Any Ideas?
Brad Croshaw
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There are a couple of things I would do first, one being a mental exercise and the other being hands-on investigation. First, ask yourself, what did it sound like before? When did you notice the noise? Was it a sudden change or did it sneak up on you? Your prop clearance is small, but if it didn't bother you before, it's not the problem unless you changed something inside the hull. If that analysis doesn't give you some solid answers, think about what's changed in the period in which you noticed the noise.
If it happened right after you had the engine and shaft work done 18 months ago, go back to the guys who did your work and show them the problem. If they don't help, hunt down the best marine mechanic in the district (note "marine mechanic" - accept no substitutes) and pay him what you may consider an outrageous amount of money to diagnose and fix the problem. Some mechanics are idiots and thieves, but good mechanics have, in seconds, fixed problems that have bedevilled me through hours of blundering amateur poking and prodding.
As to the hands-on part, if you decide not to call in a mechanic (and you may want to do some of this before you call the mechanic):
An engine guy taught me that the first thing to look at is whatever you've been messing with recently. New cutlass bearing, prop shaft and engine mounts? Check them first.
<ul><li>Run the engine at various speeds with the shaft engaged, then uncouple the shaft and do it again; get a sense of the sound compared with the sound made with the shaft in place. That may give you a sense of the source.
<li>Check the mounts - are they secure?
<li>Check the alignment (bad alignment makes a shocking amount of sound and vibration and thus would be my first guess as the source).
<li>Haul the boat and check the p-bracket, the cutless bearing and the shaft (you may have to pull it and get a machine shop to check it for true - bad alignment can throw a shaft out).</ul>
Good luck. (Oh, and from what I've heard from a former owner, a Trapper is more like a Mark I with a quarterberth instead of an icebox - check the dimensions in Evolution and foil shapes against those shown in Guide to Marks if you're interested.)
David Weatherston
Towser, Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
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Brad: A couple of thoughts: The 3/4" clearance is , as David mentioned, "small". Ten percent of prop diam. is a minimum to avoid the nasties associated with being this close. But, it worked ok before---right? You mentioned you had work done 18 mo. ago. Cutlass bearings can last 20 years-----that is if you are not running in "mud"---and you dont change a known good alingnment. When you have an existing 3/4" clearance---any little change you make in the drive train can cause accelerated cutlass wear---and a severe reduction in your already skimpy clearance. Check and see if your stuffing box got changed or re-packed--if you are not familiar with how these things work, check with someone. Best, DaveDave Tinder
DAWN BREAKER Mk3
Ft Myers
Thanks for yout feedback,
mine is an early trapper from 1973, doesn't have the quarter berth like the later trappers and has a lead keel, the info on this site has been very informative.
The noise appeared at the end of the season after a year with the new cutlass, shaft and mounts. I hadn't done any work or maintenance immediately before it appeared, hence my thinking it was fouling.
When the engineer did the work we noticed there was some wear to the side of the outer end of the stern tube. The mechanic said he would re-allign the shaft and engine but later reported that he was unable to do the work because of the beds, there was no room for adjustment.
Whilst the boat was out recently I checked the bearing by trying to detect any sideways movement around the bearing whilst applying sideways back and forth force, there was very little detectable movement, nothing I found alarming. When I rotated the prop the was some noise but nothing like what I have been hearing whilst the motoring, maybe this is because I wasn't able to rotate the shaft fast enough by hand.
I am fairly tuned into the normal running noise of the engine and this is definitely additional, i've done some simple listening tests and the noise is only there when the prop is rotating, in forward and reverse, at any speed but gets a bit more aggresive as the speed increases. I've also laid on the dockside and next to the boat and can hear it resonating through the hull. It is cyclical and ryhtmic but not in tune with prop rotation as such, it sounds a bit like when a worn ball bearing is spun fast and some rumbling chatter is audible.
I had the stuffing box re-packed and the rubber hose connection between the stern tube and stuffing box replaced at the same time. When I observe the coupling/ stuffing box area from within the locker there is some vibration movement but I assume this must be fairly normal for a small 2 cyl diesel.
I don't mind engaging the services of a good mechanic and paying for a good job but as I've just paid out for a haul, storage and relaunch and I've moved ports away from the original mechanics, I'm trying to decide whether it is something I can safely live with till the end of season haul or is it in danger of rapid deterioration and failure which requires immediate attention.
Thanks, Brad
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A long shot: While the engine is running and the prop is making "noise"----------I want to say "step on the engine"---but impossible on a 27 as we all know---point is put some pressure of some sort on the engine---trying to sudue its nature of jumping all around the compartment----try a 2X4 or some other lever in an attemp to alter its natural movement----see if the noise changes to any degree.Dave Tinder
DAWN BREAKER Mk3
Ft Myers
Good call, went to the boat today and threatened it with a lump of 4x2 and it shut up, so, sideways pressure on the rear of the engine stops the noise. I presume this means alignment, is it ok to ease the rear engine mount bolts and gently shift engine or am I just going to create a problem elsewhere?
Thanks
Brad
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Brad: Engine alignment is a "multi step" process at best. There are an infinite number possible locations---but only a finite number of things that can be "moved". The desired result is, of course, or at least in most cases, that the centerline of the engine's output be mated, coupled, matched, or whatever, to the centerline of the rest of the drive train.
For starters: Remove the 3 or 4 bolts/nuts that couple the transmission output flange to the prop shaft flange (these should be grade 8 fine thread---dont replace them with anything but). These mating flanges generally come together with some sort of male/female alignment arrangement. Most likely you'll need to insert a slotted screw driver blade to get them apart---maybe even a little "taptaptap" if they are uncooperative. This is important: Mark both flanges PRIOR to separating them. As they come apart--and are totally independant of oneanother----notice what the shaft does---droops, sags, raises, goes of to one side, etc. What we do ultimately is not nearly important as to what we do NEXT. The goal is to get those two flanges to "meet" with no more than 0.003 inches misalignment. There is a process to achieve this---if possible. My guess is that during your installation the mechanic could not or would not get it right---and said "close enough"----the engine and drive train are trying to "get comfortable' and their "disageement" has manifested itself over time. I'm not an expert---but I have a PhD in engine alignment that is awarded all those that spend 6-10 hours upside down in tiny places. If you need further help----we'll try. Good luck.Dave Tinder
DAWN BREAKER Mk3
Ft Myers
Well put, thanks, when the mechanic did the work he had to drill the old coupling off due to rust. I'll have a good look when i'm at the boat in the week.
Thanks again for the 'distant diagnosis'
Brad Croshaw
'Much Ado' Trapper 500
UK South Coast
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You are quite welcome. Now on to the possible fix----
Nine times out of ten one can adjust the engine mounts to get the desired results. You already know that these little diesels jump around like BB's in a coffee can---therefore---the mfr's use very soft mounts trying to subdue the little beasts. This being the case, it is important that you let the forces of nature bring the engine to its final resting place on its mounts---you can threaten the little guy again with your 2X4--and the mushy mounts will flex enough to let you think you've got it right. Sorry---gotta go----but where we are heading is to make sure the mounts are secure on the stringers----prior go going further.Dave Tinder
DAWN BREAKER Mk3
Ft Myers
---continued after recess: Generally, engine mounts are lag screwed to the stringers and it is rare to see these coming loose unless something really ugly has happened. A good case of "ugly" is usually some form of marine mechanic without the skill nor the desire to get it right. Lets assume your mounts are secure. Not all mounts are adjustable---some mfr's only give you 2 out of the 4 that can be adjusted laterally. Those that can be adjusted side to side are usually aft---there is probably some sound engineering here somewhere---but I'm convinced its done that way just to put them out of arms reach and make us mizerable. At this point we have 4 mounts that adjust "upanddown" and 2 or 4 that adjust "sidetoside". Don't assume that the threaded bolt coming up from the mount is securely vulcanized in its rubber base---nor should you assume that the "pad", "ell", "angle" or what ever is securely attached to the engine. After checking all this stuff its now time to see if its "possible" for that engine to sit on those mounts attached to those stringers and allow for those two flanges to meet the 0.003 tolerance. Simply, is there enough adjustment in this whole mess to line up the flanges? If you're good to go at this point go out and get 100 monkey's each with 2 big open end wrenches--and put them down in "there". My experience is that they stand some chance of getting it right----my chances are far less than random. It is all pretty much common sense---but easier said than done. One other caveat---make sure all the flange faces are perpendicular to the centerline of the shafts. The transmission side is usually ok----but the prop shop has to "fit/face" the shaft side flange. Check the stern tube for wear.
Put the mess back together and go sailing!!!!!! Best,Dave Tinder
DAWN BREAKER Mk3
Ft Myers
Dave,
just checking back with an update, spent today in the lockers and jumping up and down the companion way without steps, only got stuck once, I don't know how I managed to get so far in but for a while it was some pretty tricky reversing. Anyway I've had quite a bit of success, the mechanic was talking rubbish, there was up and down and side to side adjustment available on all 4 mounts, she's quitened down considerably just a bit of noise at lower revs when the engine is lumpy so i'll probably have another crack at it (and really stuff it).
Thanks
Brad
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