The Boatist

Sailboat Ownership, Translation Work and Tales of Minor Adventure

Retire early, be passionate, don't worry, die poor

Friday, January 15, 2016

The Oberdorfer Pump Mechanic

Why does a 30-minute job take 4 hours on a sailboat? 

This is how I replaced an Oberdorfer N202M-07 raw water pump that cost me the incredible sum of €486.
($266 for the pump + $127 for UPS freight + €118 customs + €9 credit card fee).

changing an oberdorfer pump n202m
Pump housing plate, with the pump already removed from the Universal 5444 engine (Kubota 1902 block).
1. Position, light and tools
I had to work on my knees with kneepads, needed a good source of light and had to search for a number of tools stored in what could be the largest (7 x 3 feet) and most disorganized tool box ever to exist on a sailboat.

2. Corrosion
For 14 years, the pump has been intermittently dripping salt water onto the lower 1/2 inch mounting bolt. Its head has become severely corroded, deformed and slightly stripped. The stripping part probably happened in the Azores where I removed the pump in an attempt to fix it.

The 1/2 inch wrench did not work so I tried using vice-grips. The bolt did not budge, but I managed to strip the head some more. Then I tried some metric socket heads and, you guessed it, mangled the head even more. Out of desperation and frustration, I selected a metric socket that was a touch too small and started hammering it onto the head. And, by God, it worked (but now I can't extract the bolt from the socket).

3. Finding an imperial bolt in a metric country
So now, with the pump off, I needed a 1/2 inch bolt of the same length which, incredibly, I found at a nearby car parts shop. I noticed that it weighs a lot less than the original bolts - obviously it must be made of superior quality Chinese material.

4. Scavenging parts
The new pump did not come with hose ports, which I needed to scavenge from the old pump which I clamped in a vice.
The hard part was placing the hose ports on the new pump at an angle matching the hose connection directions, which implied placing the exact amount of teflon tape so that the port would be nice and tight at the perfect angle.

oberdorfer marine pump
You can see 1 of the 2 accesses to the cluttered toolbox, which occupies the cavernous space under a long settee. I also have other smaller tool areas here and there.
5. Disorganization and bad memory
Although the pump came with an engine-to-pump gasket, it wasn't in the box. I looked in my gaskets bag but couldn't find it. No need to panic, the boat is only 39 feet long and I have all day. After searching everywhere, some places twice...nothing! Then I gave the gasket bag one last shot and there it was neatly packed in a thin envelope that looked like a piece of paper. At that moment, I wished I had beer or wine aboard, but I didn't.

6. Cleaning
The plate is attached to the engine with four bolts in cavities filled with muck and goo. I cleaned them out, drenched them with WD40 and then anointed the cavities with oil using Q-tips. Then, after sanding the pate surface with 400 metal sandpaper, I was ready for the big event.

7. Assembly operation
This was actually pretty easy; I simply followed the instructions I printed out from a website: Align engine slot with the pump slot; insert pump with bolts and gasket; tighten mounting bolts until finger tight; open sea-cock and start engine at low revs to allow the pump to self-center; lastly tighten bolts with a wrench while engine is running without losing your arm in the pulley belt. That's it! 

Port of Peniche

I was a happy man watching a copious flow of water gushing from the exhaust outlet.

Time for a late lunch and a walk around the port before cleaning up the huge mess.

Peniche Port Entrance


  1. Horacio, man, I'm sorry, but I got a good laugh with your bolt removal. Been there so many times it ain't funny. Hammers rule! The whole mess of an Imperial engine in a metric world is.... aww forgetaboutit!
    Running the engine before tightening down the pump seems interesting. I'll run that by my Man. Maybe that's why my coupling broke a couple of years back. My water pump has giving me such grievance it ain't funny. Finding imperial seals is next to impossible and the metrics leak. 5 bills is a lotta dough though.
    I'm still crying looking for my "made of gold" winch grease... but I've always got beers aboard and on my boat day I crack one open at noon sharp whilst strapping on the knee pads!

    1. Well, if we didn't have a good laugh about this "sailboat madness", there'd be no fun in it.
      But, when you think about it, if my old jeep gave me 1/10 of the work my boat does, I'd douse it (the jeep) with gasoline, light a match and start walking. Is there a sailboat rehab organization???

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