Fuel Boost Pumps

[Skymaster337B]

If it were a dangerous condition it probably would be an AD by now. Most times a SB is for the manufacture to extort money or to cover their own butts for screwing up. The fact is, if your electric boost pump fails the airplane will keep flying...the only reason it is installed is for back-up of your engine driven fuel pump. I know, you use it for engine start; but it can start without it too, using the primers.
The electric pump is designed to leak fuel overboard, out of that little vent if the diaphragm seal leaks. My view is fly it to failure...it's a Skymaster after all...if it's not broken then don't fix it. But! If your pump is leaking fuel (mine did) then by all means replace or repair the pump...or if it fails then replace it right away too. Besides your pump has lasted this long...so it probably isn't the type discussed in the SB...or the SB was an extortion attempt.

Hi, Just a bit of FYI. The C337 maintenance manual says to replace these pumps every 10 years. Here in Canada, if you fly them commercially it's a requirement. Privately, it's at the owner's discretion.

[sunnysky]

I have a 337G with Dukes auxillary pumps.
There was a requirement to replace these pumps because of broken vanes which could then go further into the fuel system and cause the mechanical pump to stop working, then engine failure !!

[billsheila]

I was aware of that Service Bulletin (note it apparently never reached the level of an AD). Any new pump was apparently supposed to be labelled to indicate it had the new type of vanes. I couldn't find these on my pumps. In the end, even though the old ones were working fine, I opted to replace them for the peace of mind.