OK, so it's about time to tackle the newest problem that's come up. Looking for some tips from y'all before I dive in....
Clue #1: Previous owner had told me a story about how his bellows-type
shaft seal started leaking while underway - and he couldn't get it to stop. So he had it replaced with a new type Lasdrop carbon seal unit.
Purchase survey said the running
gear was fine (don't they
all say that?)
Clue #2: PO says the guy came down and installed the new seal while they were still waterborne. Hmmm.... the Lasdrop instructions say that's a no-no...
Clue #3: When the shaft is turning I can visibly see runout at low
RPM. Seems to settle out at higher RPMs but is still there. I wonder if that's more than just normal thrust torque I'm seeing... Does not seem to be more or less than the way it was when we bought the
boat.
So fast forward about 100 hrs of motoring later. I take the
boat to
haul out, get her a haircut and then splash again. Quick 1-day round trip.
Clue #4: While she's hanging in the slings, I turn the prop by hand and feel a resistance through one portion of the circle - seems to be about 30 degrees of rotation where things bind up a bit. Doesn't seem real bad but enough for me to notice.
So, splash back in and boy she moves faster through the
water now with the clean hull! But yikes, the
shaft seal leaks.
Clue #5: Seal
leaks LOTS when under load.
Bilge pump keeps up just fine but I really don't like
water coming into the people tank like that. While at low / no
RPM all is dry (thankfully).
Clue #6: No abnormal vibration heard / felt after the haul-out. All seems the same except for the leaking shaft seal.
Clue #7: Come to think of it, the
engine used to spin happily up to 3200 RPM under load. Now I get black smoke and increasing temp around 2200 RPM. She will not go past 2300.... this can't be good. However, prior to the haul-out this was also true.
So now it's time to repaint the bottom and address the seal issue. As I've thought about it, the scenarios could be (from least to most severe):
a) Since the new seal was installed while waterborne, I just need to readjust it properly while out of the water this time.
b) I need to re-align the shaft and then readjust the seal. If the resistance is gone when I turn the prop after that, then all is fine.
c) The new seal is toast and will have to be replaced. Nothing else really wrong. Will have to break the coupling to replace the seal, then realign the shaft.
d) The
motor mounts are sagging and will have to be replaced if I'm ever going to get the shaft run-out down to spec. (By the way - how much run-out is acceptable?)
e) The cutless bearing is shot and is the cause of misalignment / seal leakage.
f) The shaft is bent / warped and it trashed the cutless bearing so bring a big check book....
Being the
newbie that I am, I've never done an alignment before and don't have the gages or mounts I'd need. Will probably hire that done but wouldn't mind doing it myself.
Any thoughts / tips / probable causes you folks can share? As always, many thanks in advance for your replies!
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