Impellers Again

[Ken Juul]

I've been reading Ron's tales of eel grass (EG).  Didn't quite get the picture because I had never experienced it.  Not a virgin any more.  Had the family out on the Chesapeake for a week.  Because we had the time, explored the eastern shore.  EG was every where.  For you other coast sailer's, it is like a floating island of kelp, but much finer.  More like the weeds/bad grass that grows by splitting into a thousand runners that split at every knuckle. 

I left a dock, must have sucked a bunch of EG up while warming the engine/untieing lines.  Noticed the temp was running 10° hotter than normal, stopped in the middle of the bay (no wind) to investigate.  Pulled a significant plug of EG out of the strainer/intake.  Reprimed the the pump and restarted the engine.  Water flow out the back was not normal.  Shut down again and pulled the impeller apart.  The pictures show the condition of the Globe impeller.  It was less than 3 months old, never run dry.  It probably ran 20-25 minutes at less than full water flow and never saw temps above 170°.  Not buying the 15 minutes run dry.

To make matters worse, burned out my back up rubber impeller the same way the next day.  We were anchored in a creek with very brown water.  That's the way it is here because of the tanins and the lack of current.  2-3 inches of visability is normal.  After a few phone calls, we resorted to Towboat US.  Even though we have "unlimited" towing it took over an hour of talking with different supervisors to get approval for the 25 mile tow home.  There was not a impeller available within a 120 mile drive of where we were located and it was Sunday so it would have been an over night wait. They eventually agreed, our only claim in 11 years of boat and towing coverage. 

Had a new impeller delivered by a friend who picked it up on the way to the marina.  Finished the vacation, all in all a wonderful time.  Moral of the story. Either Globe has changed their manufacturing process or there is no such thing as a run dry impeller.  If you suspect you have had blockage of the raw water cooling system, check the impeller before you restart the engine.  Spares are a wonderful thing, wish I had 3 sets of impellers and Heat Exchanger gaskets instead of just 2.  It was my first "experience" in 9 years on the bay, there is always something to experience and learn.

Legal Disclaimer:  Not dissing Globe.  They are cheaper than comparable rubber impellers.  Just not buying the marketing claims any more.

[prh77]

Mainsail had a thread about the Globe impellers a while ago. I think his issue was also hubs spinning. I have had the best luck with the Orberdorfer units. Assuming one has that brand of pump of course.

[Ron Hill]

Ken : I was told some 23 years ago by a Universal Marine part supplier that : "Impellers are like light bulbs" some will last a long time and other will fail immediately!  

I've had great life out of the black and the Globe impellers.  However, I take my impeller out of the pump at winter haul out.  I spray it with silicone, set it in a shallow cup and let it set under the engine till spring.
In spring I take the impeller off the shaft, inspect it and REVERSE it when placing it back on the shaft.
Then reinstall the shaft and impeller back in the pump, placing waterproof grease on the pump faceplate and inside surface.  
I also store my extra impellers( I carry 3 or 4 extra) in a ziplock bag after I spray them with silicone - that doesn't let them dry out!!!

Needless to say that a simple bronze strainer caulked lightly to the underside of the hull's raw water intake, could have prevented your clogg!!  

A few thoughts.  

[Stu Jackson]

I'm pretty sure Ken has a strainer on his raw water intake.  Are you saying, Ron, that a bronze one is better and will prevent eel grass from getting through, compared to a plastic (OEM - probably a Sherwood) one that most of us have on our boats?

[Ron Hill]

Stu : All of the C34s that I've seen, have a Hypro Series 3350 nylon line strainer as OEM from the factory.
That strainer is attached to the inside of the hull on the raw water thru hull, just above the thru hull shut off lever and has a clear screw-on bowl with a SS strainer inside.

I've written up the advantages of an exterior raw water strainer on the outside of the hull numerous times.  I also have recommend that it be held on by caulk rather than screwed in to place.  That reason being so that if bad went to worse and that clog was sooo bad, all you'd have to do is take a 3/8" wooden dowel and knock off that round bronze strainer from the inside.
 
In past articles I've even listed the WestMarine sku # of that bronze strainer and cautioned people that if they decide to mount one - don't forget to use bottom paint on the inside of that strainer before lightly caulking it in place.