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williamlweaver
User Rank
Platinum
Re: Leaky boat
williamlweaver   1/10/2012 3:19:10 PM
NO RATINGS
I hear you LarryR46. My parents purchased a new 1979 Aristocraft with a 170 hp Mercruiser I/O and we used it trouble-free through the 80's. What surprises me is that something that is so obvious to boat owners would not be easily detected/predicted or anticipated by design engineers. As is the case which Agile software development attempts to address with customers on the development team, I wonder how many of the Volvo engineers were actually boaters -- much like the problem of software designers that build user interfaces for bench-top laboratory instruments never having stepped foot in a chemical laboratory.

LarryR46
User Rank
Iron
Re: Leaky boat
LarryR46   1/10/2012 11:53:17 AM
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Mercury outboard moved their PT hydraulic fluid (very much like auto xmission fluid) reservoir from inside the boat to outside the boat around 1980, depending on the model.  Since Volvo-Penta's original IO design was mostly high-jacked from Kiekhaefer in early 60s, it's fitting that Volvo should copy mercury marine's trim design albiet somewhat late.  The outside reservor is a much cleaner installation than the older external one with very many fewer connections and hyrdaulic fittings to leak.  Most of the leaks occur in the three actuating cylinders which would be outside the boat in either case.  I agree that leaking ATM is BAD for the environment and more effort should be put forth to eliminate leaks.  I'm not sure that keeping the reservoir inside the boat does this, however.  Making the replacement of seals in the actuating cylinders more straight-forward would also help.

Dave Palmer
User Rank
Platinum
Re: Leaky boat
Dave Palmer   1/10/2012 10:30:02 AM
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@Beth: If it's a hydraulic trim unit that's leaking, then I assume that what's leaking is hydraulic fluid.

Some dissimilar amorphous plastics can be ultrasonically welded, if they have similar chemical structures and if their melting points are within 50°F of one another.  But from the description, I'm guessing that at least one of the plastics is a glass-filled nylon, which is a semicrystalline plastic (not amorphous).

Moisture content can be a big problem in ultrasonic welding of nylon.  Nylons can absorb a significant amount of moisture from the atmosphere.  When the material is welded, the water turns into steam, which leads to a weak and porous weld.  This can be avoided by welding in the "dry" state immediately after molding, before the material has had an opportunity to absorb any moisture.

Glass content can also make ultrasonic welding more difficult.  Many ultrasonic welding equipment manufacturers won't recommend welding anything with more than 20% or 30% glass, although it is actually possible to do so.

Glancing briefly at Volvo-Penta user forums, it seems like many boat owners have encountered this problem.  The best solution I've come across seems to be to remove the welded plug, drill and tap the housing, and put in a metal plug.

Rob Spiegel
User Rank
Blogger
Re: Leaky boat
Rob Spiegel   1/10/2012 7:19:11 AM
NO RATINGS
That's a good question, Beth. I suspect it's oil. If it's gasoline, boats might be blowing up in the water. I asked the author of this Monkey posting to weigh in. Hopefully we'll get the answer soon from the source.

Beth Stackpole
User Rank
Blogger
Leaky boat
Beth Stackpole   1/10/2012 6:41:37 AM
NO RATINGS
What exactly is leaking into the river--oil, gasoline, what? Sounds like this could be one of those examples of designers caught up in the feature chase or redesigning for redesign sake without really considering the broader ramifications of their efforts.

 

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