Hey all, new owner (or soon to be), and I am replacing the impeller in the Oberdorfer raw water pump. The impeller came out easy enough. Any tricks to sliding the new impeller in to the housing? Seems like I should clean out the housing real good, clean the cover and swap out the old ring gasket for a new one. Also seems like I should put some kind of lubricant on the impeller itself, as it will be rotating a little bit before its fully wet. What do you use to lube it?
Mike
1999, Tall, Wing, In-Mast Furling
Phinneys Harbor, MA
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Jackfish Girl, 1999, C36 MKII, Tall Rig, Wing Keel, In-mast furling, Monument Beach, Bourne, MA
A little vasoline will work. Apply some to the impellor sides and either the pump housing or a dab on the end of the fins. Also, while you have the faceplate off, run your fingernail over the area in contact with the implellor to check if any wear is occuring. If there is wear, polish the face plate flush.
Paul & Wendy Keyser
"First Light"
Rye NH
2005 C36 MKII #2257
Wing, M35B
Great advice, as always. Thanks again. I'll be at it tomorrow. I'll check for wear on the inside back of the faceplate.
Mike
Jackfish Girl, 1999, C36 MKII, Tall Rig, Wing Keel, In-mast furling, Monument Beach, Bourne, MA
I had a C30 with an M25 cooled by an Oberdorfer. It had about 600 hours on the pump ( with multiple impellor changes). For three years, I experienced intermittent engine overheating. I replaced or inspected all the hoses, impellor, temp guage, strainer, exhaust riser, muffler, engine antifreeze pump and other things numerous times but nothing fixed it. This drove me crazy and it was dangerous- like when transitting the Cape Cod Canal with freighers bearing down. Then, the mystery grew deeper. I found I could make the engine overheat when I turned the boat hard right. Hard left had no impact. It turned out the Oberdorfer face plate was worn (weakening the suction) and the placement of the keel and raw water intake broke the suction on hard right turns. The face plate had maybe .010"-.020" of wear. The oposing pump face probably had the same amout of wear and it was enough to cause intermittent suction loss. Sanding and polishing the face plate to a flat surface fixed the problem for the rest of my ownership. The Oberdorfer on our current boat has a two sided plate to flip to the unworn side if necessary. The older pumps had cast bronze face plate that were not reversable.
Paul & Wendy Keyser
"First Light"
Rye NH
2005 C36 MKII #2257
Wing, M35B
Wow, thanks for sharing Paul. I put the face plate back on yesterday and realized I didn't mark which way was up, In other words keeping the faceplate in the same orientation going back on as it came out. Wondered to myself if it would matter. I fid in fact clean it real well and replaced the thin O-ring. Hopefully it's sealed..
One issue I had, since this was my first go at this, was getting the little retaining clip back on. It's probably common knowledge within this forum that when sliding the new impeller in to place the pump shaft the force seats the shaft back in to the engine just enough so that the groove for the retaining clip is concealed by the impeller hub. (design flaw?). I called Oberdorfer, nice guy at tech support, but he didn't really know what I was trying to tell him, he did give me phone numbers for boat yards where the guys would know. Anyway, the solution was to apply some Vaseline to the shaft (stop giggling please), and then slip my longest flat head screwdriver into the slot at the base of the housing and applying just a slight pressure to the shaft to prevent it from moving, I was able to slip the impeller on to the shaft and have the groove exposed. I pressed the clip on the same way, then pushed the entire slippery mess into the housing so it was fully seated.
Anyone experience this? Yes, I'll be inspecting the pump with a keen eye after first engine start. (next year I probably won't replace the impeller until it's actually in the water).
Mike
Jackfish Girl, 1999, C36 MKII, Tall Rig, Wing Keel, In-mast furling, Monument Beach, Bourne, MA
Special Snap Ring pliers are made that make it easy to reinstall the ring on the shaft. You can get them from a car parts distributor like NAPA or Autozone. Finesse will work if you don't have pliers, but it's common for the ring to pop out of the pump and bounce around the cabin sole when trying to seat it. Beause the impellor is firmly held held in place by the pump housing when the face plate is mounted, I've heard comments from some that they don't even bother replacing the snap ring.
Paul & Wendy Keyser
"First Light"
Rye NH
2005 C36 MKII #2257
Wing, M35B
I have the pliers, no problem there. I guess I'm having a hard time describing what's going on...When pushing the impeller onto the shaft, the shaft seats back in to the engine, so far that the groove for the clip isn't exposed, it's covered by the hub of the impeller. I was able to hold shaft out just enough to get impeller and the clip on, then pressed it all back in. The fact that no one has come across this leaves me a little concerned. Maybe everyone just pulls the shaft out with the impeller and slips the impeller on to the shaft in hand, then slides it all back in?
Mike
Jackfish Girl, 1999, C36 MKII, Tall Rig, Wing Keel, In-mast furling, Monument Beach, Bourne, MA
Mike-
That is one way to do it. Just be careful when you slide the shaft back in that you don't damage the seal on the back side of the pump. (Otherwise, sea water will find its way into the engine.)
I think the impeller shaft mates with its drive shaft (the end of the valve cam shaft perhaps??) in the engine via a slot and key on the ends of the shafts, so you shouldn't be able to push the impeller shaft too far into the engine, but yes, far enough to make it difficult to reinstall the snap ring.
Paul & Wendy Keyser
"First Light"
Rye NH
2005 C36 MKII #2257
Wing, M35B
David S. Power
Two If By Sea #1687
Burnt Store Marina
Punta Gorda, FL
I guess you've done the job already but the other thing you have to look for is which way the impeller blades are bent before you take the old impller out. Other wise, you could put the new one in with the blades facing the wrong way.
Chuck Parker
HelenRita 2072 Mk II
2002 Tall Rig - Winged Keel
Atlantic Highlands, NJ
Not sure that's much of a concern. Once the pump shaft begins rotating the blades will sort themselves out -- you can view this if you rotate the engine back and forth by hand while the pump cover is off.
Matthew Chachère
s/v ¡Que Chévere!
(Formerly 1985 C36 MKI #466 tall rig fin keel M25)
2006 Catalina Morgan 440 #30.
Homeported in eastern Long Island, NY
Yes! I was so paranoid doing this for the first time, I took pictures every step of the way. But I ensured the fins were swept in the the correct direction.
There was a forum post on another site that warned about not allowing the shaft to come out all the way or you would have to remove the entire pump. I just don't think it's the case with the model I have. So I'm thinking it would probably be OK to allow the shaft and impeller to come out in one piece and reassemble it in your hand, lube it up and stuff it back in. Thoughts? Thanks!
Jackfish Girl, 1999, C36 MKII, Tall Rig, Wing Keel, In-mast furling, Monument Beach, Bourne, MA
"There was a forum post on another site that warned about not allowing the shaft to come out all the way or you would have to remove the entire pump. I just don't think it's the case with the model I have. So I'm thinking it would probably be OK to allow the shaft and impeller to come out in one piece and reassemble it in your hand, lube it up and stuff it back in."
That's been our experience. Sometimes the shaft comes out when you remove the impeller, but not a big deal to just stuff it back in.
Matthew Chachère
s/v ¡Que Chévere!
(Formerly 1985 C36 MKI #466 tall rig fin keel M25)
2006 Catalina Morgan 440 #30.
Homeported in eastern Long Island, NY
Les & Trish Troyer
Mahalo
Everett, WA
1983 C-36 Hull #0094
C-36 MK 1 Technical Editor.
Commodore
Thanks so much. Much more confidence next time!
Mike
Jackfish Girl, 1999, C36 MKII, Tall Rig, Wing Keel, In-mast furling, Monument Beach, Bourne, MA