View Single Post
  #6   IP: 142.68.126.98
Old 12-31-2008, 06:07 PM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
On the big twin power boat we had for a decade, I changed them annually, owing to a bad experience first year or two and a fair bit of summer cruising. For this smaller engine, I like Don's advice from the MMI pump instruction kit, and I dreamed up some additional reasons to change the impeller. Here is my personal checklist:

1. Fins appear stiff, cracked, have a pronounced "memory" (bent lobes), or any other sign of damage.
2. Every two years of average summers in clear water.
3. Every 200 hours (= 800-1000 miles under power), more often in sandy water.
4. Episode of running pump dry more than a few seconds (during startup, or episode of clogged strainer).
5. Episode of engine overheating, regardless of cause.

Remove impeller every fall and put it back in every spring, so the vanes do not remain bent up all winter (leave a reminder somewhere obvious for spring). The new MMI pump makes removal a snap.
Carry at least one spare.
__________________
1974 C&C 27
Reply With Quote