How to change the impeller on a Universal M25 XP

How to change a sherwood impeller on a Universal M25xp:

Step 1 – Attempt to unscrew the bolts holding the pump housing. Curse the designers who thought it would be a good idea to put the bolt heads on the *back* of the pump. Skin knuckles.

Step 2 – After 45min or so of unscrewing each bolt 1mm at a time, carefully slide pump housing off shaft. Skin knuckles again. Watch as important little piece that must not be lost falls out of the shaft. Fortunately you were smart enough to put a tray under the housing to catch said piece. Congratulate self on outsmarting a boat project (BIG MISTAKE!!!)

Step 3 – Install new impeller in housing. Prepare to mount back on the shaft. Watch in horror as important little piece that must not be lost goes “SPROING” and flies away, landing somewhere inaccessible under the floor.

Step 4 – Spend 15min cursing every curse in the book. Make up a few new ones for good measure. That’ll teach you to get smug with the boat-project gods

Step 5 – Spend the next 2 hours upside down in the bilge, peering under the floorboards trying to locate said important little piece that must not be lost… Remove all possible access panels/boards Acquire numerous cuts and bruises.

Step 6 – Finally locate piece. Out of reach of course. Spend the next hour rigging up contraptions to try and fish it out.

Step 7 – Retrieve the piece and re-mount the pump, while the boat project gods laugh.

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2 responses to “How to change the impeller on a Universal M25 XP

Step 8: Get rid of the Sherwood pump and convert to an Oberdorfer. You will be so happy when its just 4 screws to change the impeller.

I feel you on this one. I fought with my Sherwood for 1 year. Then I had enough and tossed it off the boat. I had to do a lot to change to the Oberdorfer, cut the base, redrill holes, etc. All you have to do is bolt it on. Worth the $250. Could you ever imagine trying to change that impeller while drifting down the ICW?

Good luck and fair winds,



Yup – I think next time the impeller is due for a change, I’m gonna just switch the whole pump out for the Oberdorfer…

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