Impeller replacement Cat 3126

Rssll45

Member
Feb 16, 2009
87
New Orleans
Boat Info
1998 450DA
Engines
Cat 3126
Has anyone figured out a shortcut to replace the impeller on the outboard side (stbd in my case)? Just did the port engine but can no longer lie across the water heater and work thru the exhaust pipes to tackle the outboard side of the stbd eng. Could it be easier to just pull the whole pump, replace the impeller on the bench and reinstall? I've been having a mechanic do it and it's close to $200. Just went though a search and 20 pages with no ideas.
 
On my 410 I remove the fiberglass section of exhaust pipe to do any work down low on that side. Takes a couple of hours to change that one.
 
On a 450DA, there should be room to crawl to the back side of the stbd engine by slowly and carefully crawling over the transmission. Once you bet back there you can squat/lay along the back side of the engine and the seawater pump is pretty easy to get to. Going around the rear of the engine and over t he water heater is much more difficult. If you have trouble doing it the way I suggest, then get used to the $200 cost because there isn't any other way.

Removing the entire pump isn't very efficient because it bolts to the engine's accessory drive and is gear driven off the engine's front end gearing. You still have to get to the back of the engine to get to the pump bolts and to realign the gear teeth when you reinstall the pump.
 
Thanks for the info. That's appears the only way to get to it, i.e., over the transmission from the fwd part of the engine room. I still have to lay across the water heater and work thru that very limited space between exhaust pipes. HUMPH, how difficult is it to remove the section of exhaust pipe? I've thought about that but never tried it. Guess if Frank doesn't know a way, there ain't one. $200 isn't a lot in boat dollars.
 
On the 410s, the stbd exhaust (long fiberglass section) has to come out to access the pump. Not hard, just takes about a half hour the first time. Additionally, for both pumps (on the 410s), a fuel line (from the fuel cololer) and the oil pressure sender have to be removed... Not sure about that on the 450...
 
Thanks for the info. That's appears the only way to get to it, i.e., over the transmission from the fwd part of the engine room. I still have to lay across the water heater and work thru that very limited space between exhaust pipes. HUMPH, how difficult is it to remove the section of exhaust pipe? I've thought about that but never tried it. Guess if Frank doesn't know a way, there ain't one. $200 isn't a lot in boat dollars.



Ive owned my 450 since 1997 so I've done several impeller changes. If there is a trick to this it is to be prepared when you climb behind the engine. Have your wrenches, rachet, extensions, sockets, screwdrivers, puller, new parts, etc. ready and laying on the aftercooler cover so you are ready when you get in position and so you only have to make one trip to never, never land. As far as removing parts of the exhaust system is concerned, changing the impeller is about a 10 minute job. I'm not a fan of doing 30 minutes work to accomplish a 10 min job unless it is absolutely the only way. While not the most comfortable position to be in, squatting behind the engine and leaning over to get to the water pump is favorable to making a long term project out of removing the exhaust system.

The one I am not looking forward to at all is changing out the water heater.....................
 
Fortunately my mechanic is a little bloke who makes the difficult jobs look simple. He also has the patience of a saint...whereas i am deficient in this area.
 
On the 410s, the stbd exhaust (long fiberglass section) has to come out to access the pump. Not hard, just takes about a half hour the first time. Additionally, for both pumps (on the 410s), a fuel line (from the fuel cololer) and the oil pressure sender have to be removed... Not sure about that on the 450...

Great design on that right? Once you understand what to remove before you start, it's not too bad...
 
Ive owned my 450 since 1997 so I've done several impeller changes. If there is a trick to this it is to be prepared when you climb behind the engine. Have your wrenches, rachet, extensions, sockets, screwdrivers, puller, new parts, etc. ready and laying on the aftercooler cover so you are ready when you get in position and so you only have to make one trip to never, never land. As far as removing parts of the exhaust system is concerned, changing the impeller is about a 10 minute job. I'm not a fan of doing 30 minutes work to accomplish a 10 min job unless it is absolutely the only way. While not the most comfortable position to be in, squatting behind the engine and leaning over to get to the water pump is favorable to making a long term project out of removing the exhaust system.

The one I am not looking forward to at all is changing out the water heater.....................
Frank, my friend with a 560DB had his water heater fail and he ended up adding a new one forward of his port engine. Amazing when they (MM) suggested pulling a motor (3406E), removing the salon decking or cutting a hole in the hull to access it! All of the above involved cutting the air conditioner bracers and welding them back together later. Relocating the power and plumbing was easy!
 
Thanks for your replies. I'm just going to get out my checkbook and call the mechanic. I'll down there in front of the engine pulling the cover off the heat exchanger to recover the always missing vanes, so I can pass him tools.
 
I am having a very difficult time just with basic impeller removal on my 3126. I am currently working on the easily accessible one. I have the cover off with 3 bolts. Next I tried using the large bolt threaded into the shaft opening but after I get it maybe 1/4" out it just seizes up. The bolt just won't turn anymore. I tried tapping it a bit with no effect. IT was suggested to me to turn the engine over just briefly but that didn't do anything either.

Any suggestions at this point would be appreciated.

Thanks

Dave
 
Spray some WD40 or other lubricant into the pump body. Bump the engine over (get the key slot as close to top position as possible before pulling impeller). With the lubricant the impeller should slide out pretty easily. As mentioned above, you need to remove the oil pressure sender and pivot the fuel line connection in to the fuel cooler (shouldn't need to remove this) to gain clearance. I pull the fuel solenoids as I do this when the boat is blocked and don't want the engines to fire when I bump them.
When installing I use a zip tie to compress the lead end of the impeller then use a silicone lubricant (generously). They slide in by hand, but don't get them too far in until you have the key-way lined up and the key inserted.
Easy on the port side. Stbd side is the same routine...just not a great working position. I change them every year and hate the job less each time.
Good luck!
 
Ahhh, impeller on the starboard, I've spent a few hours on the outside of the engine. I got stuck back there once. bring your cell phone.
 
Me too Turtle - especially when you get a charlie horse down there - I don't know whether to laugh or yell for help!!!

Do you pull your exhaust pipe to get down there? I do and I pulled the aluminum hatch brace when I replaced the pump itself. Gave me much more room.
 
I've had it done every year without pulling the exhaust or the oil pressure sender (takes the right length puller bolt). It's tedious work, but it seems like pulling the exhaust would be a time consuming messy job. Solved the problem this year. Since the Cat guy was coming to reset my overheads and recommended rebuilding the sea water pumps, I had him put a new pump on the stbd side and rebuild the port.
 
Do you pull your exhaust pipe to get down there? I do and I pulled the aluminum hatch brace when I replaced the pump itself. Gave me much more room.

Yes. Not too hard to pull the exhaust. My aluminum brace is "siliconed" in, so I haven't removed it. Seems like the throttle cable is attachedd to it as well...
 
I am having a very difficult time just with basic impeller removal on my 3126. I am currently working on the easily accessible one. I have the cover off with 3 bolts. Next I tried using the large bolt threaded into the shaft opening but after I get it maybe 1/4" out it just seizes up. The bolt just won't turn anymore. I tried tapping it a bit with no effect. IT was suggested to me to turn the engine over just briefly but that didn't do anything either.

Any suggestions at this point would be appreciated.

Thanks

Dave

It sounds like you have the wrong thread on the extraction bolt; I believe it is 3/4-16.
 
Yes. Not too hard to pull the exhaust. My aluminum brace is "siliconed" in, so I haven't removed it. Seems like the throttle cable is attachedd to it as well...

Silicone was not too difficult to deal with and the cable clamps are screwed on. The extra 30 minutes to remove was worth it! You could get down in there for short periods of time. Port side pump is a 2-hour or less project. Starboard side, more like 3 or 4 hours.
 

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