First Impeller change

[Top Hatt Craig]

Thanks all for the great advice here. Even though we weren't having any cooling problems the archives here got me going on impeller change outs, having been running on luck since March. Took a look in the trans cooler as advised and it's clear now. Surprised how hard working this pump is, seeing how far the blades are bent over at the cam.

 

[Tim Powell]

Thanks all for the great advice here. Even though we weren't having any cooling problems the archives here got me going on impeller change outs, having been running on luck since March. Took a look in the trans cooler as advised and it's clear now. Surprised how hard working this pump is, seeing how far the blades are bent over at the cam.

I always have a hard time getting the old one out. I have noticed that some have a brass threaded end for a bolt. Just for your information.

 

[Pascal]

Some impellers have a threaded core so you can use a bolt and a wrench to pull it out. Easier than the typical impeller tool

I ve always found the hardest part was pushing the new one in, at east when dealing with bigger impellers

 

[Tim Powell]

Some impellers have a threaded core so you can use a bolt and a wrench to pull it out. Easier than the typical impeller tool

I ve always found the hardest part was pushing the new one in, at east when dealing with bigger impellers

AGREE! i learned to use a little dawn which helps and tell you when and if it is pumping by looking at the exaust for suds.

 

[Walter P]

I have an impeller puller which if I'm not mistaken is made by Jabsco. It works very well on my engines (6-92). Also I agree with the use of Dawn or similar dish washing soap. It will rinse itself out very quickly and not affect the new impeller. A trick I use (not my idea, it was shown to me years ago)which works very well is to use a couple of wire ties to compress the vanes and using a pair of wire cutters (dykes) snip them off as you progress sliding in the new impeller.

Walt

 

[eze2bme]

I agree with Walt - I use plastic zip ties to compress the vanes and dawn - the zip ties usually slide up the impeller as it's being inserted. I also marked the outside top of the cover with an arrow to indicate the rotation direction to make sure that the impeller is inserted properly.

 

[scottinsydney]

On the larger impellers I can generally get them in about 1/3 by hand and then use a rubber ended mallet to tap the rest in. Works a treat.

 

[bobk]

I have never seen one fail as shown in the second picture. Any idea why?

Over the past ten years with the 48MY operating at 1000-1100 rpm and about 400 hours per year, I find cracks just beginning at the root of the vanes after 400 hours so change them once a year. I have not had a vane fail in that time.

Bobk

 

[Boatsb]

The bore and cam should be smooth. If not they will chew up impellers. Also did you check the seal, bearing and cam?

 

[eze2bme]

Leave them in long enough and they will break apart like that - especially boats that spend months out of the water in covered storage over the winter. When I bought my 43 it had always been in winter storage out of the water for 6 months - and the previous owner had changed the impellers every 3 years. When I bought it - it was at the end of the 3 year cycle. After launching and a short trip to my slip I noticed that the starboard engine water discharge was significantly less that the port engine. I changed the impellers and the one on the starboard engine had only one vane intact - the rest were downstream. I disassembled the downstream plumbing until I found all the missing vanes. I'm in fresh water and don't need to pull her out over the winter, so now I just change them every other year.

 

[jrbrein]

Has anyone had experience using "SpeedSeals" on their raw water pumps?

They use thumb screws to fasten the front cover on the impeller housing and a nitrile ring embedded in the plate cover thus eliminating the need for a gasket. This ring might be useful if you just want to have a quick look without changing gaskets.

I am thinking of installing them.

Jon

 

[MikeP]

On our 8V71TIs I pull all impellers at winterizing with a Jabsco impeller tool and drop them in a pot of very hot water. That "straightens" the vanes. I also pull the Genny impeller. After the vanes are straight I take them out and they sit on the dining room table until I reinstall them in the spring. But I buy/install new impellers every two years regardless of how good they look.

For installation, I again put the impellers in very hot water for a few minutes, then take them out of the pot, smear some lubricant on the pump inner surface and the impeller vanes. I can push the warm, lubricated impellers in by hand with no need for wire ties, hose clamps, etc.

I have often said that we all do what we are COMFORTABLE doing, regardless of what may be the "normal" or "recommended" way. I am not comfortable leaving impellers in place over the winter with no idea of their condition when the engines are restarted in the spring. I want to see/inspect them and KNOW they are in excellent condition every season.

I do NOT want to pull an impeller after some years when there is a flow problem to discover impeller vanes/bits are now somewhere in the intercooler...

 

[SEVEN]

On our 8V71TIs I pull all impellers at winterizing with a Jabsco impeller tool and drop them in a pot of very hot water. That "straightens" the vanes. I also pull the Genny impeller. After the vanes are straight I take them out and they sit on the dining room table until I reinstall them in the spring. But I buy/install new impellers every two years regardless of how good they look.

For installation, I again put the impellers in very hot water for a few minutes, then take them out of the pot, smear some lubricant on the pump inner surface and the impeller vanes. I can push the warm, lubricated impellers in by hand with no need for wire ties, hose clamps, etc.

I have often said that we all do what we are COMFORTABLE doing, regardless of what may be the "normal" or "recommended" way. I am not comfortable leaving impellers in place over the winter with no idea of their condition when the engines are restarted in the spring. I want to see/inspect them and KNOW they are in excellent condition every season.

I do NOT want to pull an impeller after some years when there is a flow problem to discover impeller vanes/bits are now somewhere in the intercooler...

Very smart.

 

[Top Hatt Craig]

I have never seen one fail as shown in the second picture. Any idea why? Over the past ten years with the 48MY operating at 1000-1100 rpm and about 400 hours per year, I find cracks just beginning at the root of the vanes after 400 hours so change them once a year. I have not had a vane fail in that time.Bobk

The inside surfaces of the pumps at 1730 hours are smooth as can be, based on my experience as a former auto mechanic, I'm confident our impellers were allowed to exceed their service interval by a significant amount of time and hours. Interestingly to me, I don't see any difference in the flow of water out the exhaust with the new impellers. This cooling system maintenance started with new screens when I found quarter size holes in them.

 

[MikeP]

"Interestingly to me, I don't see any difference in the flow of water out the exhaust with the new impellers. This cooling system maintenance started with new screens when I found quarter size holes in them."

Have you checked the intercoolers/Heat exchanger (whichever provides the first barrier) for impeller pieces that may be clogging them? Those remnants of the impeller vanes have to be somewhere... Also, have the Heat Exchangers been acid-cleaned to ensure they are not clogged with the normal deposits that accumulate over time?

Clogged HEs would restrict water flow...

And, there are the shower heads, of course.

OTOH, the important issue is: do the engines remain at safe operating temps at WOT under load? If they do, then it would appear everything is fine!

 

[Top Hatt Craig]

"Interestingly to me, I don't see any difference in the flow of water out the exhaust with the new impellers. This cooling system maintenance started with new screens when I found quarter size holes in them."Have you checked the intercoolers/Heat exchanger (whichever provides the first barrier) for impeller pieces that may be clogging them? Those remnants of the impeller vanes have to be somewhere... Also, have the Heat Exchangers been acid-cleaned to ensure they are not clogged with the normal deposits that accumulate over time?Clogged HEs would restrict water flow...And, there are the shower heads, of course.OTOH, the important issue is: do the engines remain at safe operating temps at WOT under load? If they do, then it would appear everything is fine!

Hi Mike, yep, cleaned loose vanes from trans cooler (first pics) although I'm never going to be a marine diesel cooling system engineer, I strongly suspect anything that made it through the small passages in the trans coolers would get stuck in the shower heads. I don't find our water flow restricted in any way and a recent 15 min run at 2000 rpm produced no more than normal temps (160) so other than a couple zinks I think we're good to go. Here's a pic of the Pump Cam just to show what our impellers compress against. I think it's impressive that they last as long as they do. Does anyone have anything to say about the silicone impellers?

 

[Top Hatt Craig]

Hi Mike, yep, cleaned loose vanes from trans cooler (first pics) although I'm never going to be a marine diesel cooling system engineer, I strongly suspect anything that made it through the small passages in the trans coolers would get stuck in the shower heads. I don't find our water flow restricted in any way and a recent 15 min run at 2000 rpm produced no more than normal temps (160) so other than a couple zinks I think we're good to go. Here's a pic of the Pump Cam just to show what our impellers compress against. I think it's impressive that they last as long as they do. Does anyone have anything to say about the silicone impellers?

Edit: anything that made it through the small passages in the trans coolers would NOT get stuck in the shower heads. But who knows?Regards, Craig