Forum Index
The Boater's Guide to Information, Education & Scuttlebutt...
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Mercruiser 350 MAG MPI Tow Sports Sea Water Pump Impeller

 
Post new topic   Reply to topic     Forum Index -> Mercruiser
View previous topic :: View next topic  
Author Message
CC553



Joined: 07 May 2007
Posts: 2

PostPosted: Mon May 07, 2007 8:18 pm    Post subject: Mercruiser 350 MAG MPI Tow Sports Sea Water Pump Impeller Reply with quote

Has anyone heard of an impeller (within the raw pump assembly) changing the directional rotation of the individual fins during boat operation? I have had this happen to me at least 6 times over the past year. 3 burnt up impellers and several tows later I can't explain this problem.

When symptom occurs (Not always), the boat has been turned off, the motor is hard to start, the belt begins to squeal and slip. What has happened from experience, I have found the impeller fins change direction in the pump. this causes the pump pulley to become very difficult to turn and starts smoking the serpentine belt. The only fix is to remove the pump from the motor (V-Drive Boat), remove the pump cover, pull out the impeller (Sometimes still good) and reset with the correct directional rotation. Keep in Mind Motor does not Diesel when turned off.

Local Mechanic said Boat Checked out fine on ECM555 Scanner. No apparrent problems. Could not find problem with impeller. Ironically, First trip to the lake after service, the impeller problem re-occurred right on the trialer from initial start-up. I Became angry and hit the top of the slipping belt with my fist (Very Dangerous) while motor was running. after the 2nd hit, the Sea Water Pump reversed and immediatley began to run perfect.

Your feedback will be greatly appreciated. Thanks.
Back to top
View user's profile Send private message
boatScotty
Senior Member


Joined: 07 Nov 2006
Posts: 229
Location: Pacific Northwest

PostPosted: Tue May 08, 2007 10:02 am    Post subject: Reply with quote

OK, I need to ask some questions about your engine - and it's functioning.

Let's leave the impeller 'problem' aside for a second. I need to confirm what I am hearing you say.

1. When you describe your impeller as 'burnt up' - do you mean the vanes are gone? Are the vanes snapped off? Or is there rubber fused to the sides of the impeller housing?

I would look at the impellers the very next time you felt the reversing and see what they have done, and check for the impellers cracking.

2. You said a mechanic tested your engine with the EMC555 Scanner "The state-of-the-art ECM555, one of the most powerful engine-control modules on the market, not only monitors vital engine functions to deliver the right amount of fuel, it also protects the engine with its Engine Guardian system in case something does go wrong."
Yet, you are also stating that the 'motor is hard to start' after running when cooled or running then restarted hot? I would check your timing right there as a first step (I will tell you more about why I think this later).

3. Finally, you told me something truly unique! "I hit the top of the slipping belt with my fist (Very Dangerous) while motor was running. after the 2nd hit, the Sea Water Pump reversed and immediately began to run perfect". Wow, I have never heard of a pump running backwards (is that correct?) while the belt is trying to turn it the other way. I suspect what I am stating below has happened.

So here are some things I know. There are times during shut off, on an engine that is high compression AND runs on AND has it's timing off that the engine as it stops will do a little reverse run (maybe a revolution or two at most) with the matched 'wheezing' through the intake. If this were the case, your impeller would have it's fins reversed at shut down BUT should snap back (think, the torque that reversed them is less than righting them) when you start back up. Indeed, your striking the belt (essentially increasing the grip on the pump) snapped the impellers back to the correct orientation.

So, the real question is what is your engine doing at shut down that reverses the impeller?

Simply put, tell me as much detail as you can - I think the impeller is a symptom of something else. Check timing. Pay attention carefully what happens at shutdown.

Finally, I have presumed you are not just running it dry or something similar to cause damage.

Boat Scotty
Back to top
View user's profile Send private message
CC553



Joined: 07 May 2007
Posts: 2

PostPosted: Tue May 08, 2007 3:03 pm    Post subject: Mercruiser 350 MAG MPI Tow Sports Sea Water Pump Impeller Reply with quote

boatScotty,

Thanks for your response, please allow me to be more specific with question # 1, Please Note: all impellers were changed out within 3 months time.

1st impeller - vanes are gone, impeller looked to be dry-rotted (probably seasonal replacement necessary)

2nd impeller- My fault, when I removed sea water pump to open up to reverse the vanes, I forgot to re-open the ball valve to open the fresh water flow to the sea pump. Wonít make that mistake again. Vanes were gone. (Impeller looked fine during removal and reassembly procedure, Vanes were just reversed.)

3rd impeller- currently works fine (Vanes reverse during every outing). Every time I have had to open the pump vanes always look ok.

RE: #2 Iím not sure how to adjust the timing on this motor. I thought the ECM555 control advances or retards the timing accordingly. Is there a way to perform a timing procedure on this motor? and 2nd, should a timing problem have showed up on the 555 scanner with the mechanic?

RE: #3 I took a shot in the dark out of frustration. Probably stupid, but it worked. This will probably resolve the need for removing the impeller housing every time this problem occurs, and yes, I am 100% certain that the vanes reverse their directional rotation.

I have discussed this problem with several mechanics, some have told me this is impossible (Not True), most have never heard of this occurrence, the dealer told me the problem was due to a faulty IAC valve (Showed up on the 555 scan, replaced it, boat definitely idles better) impeller problem still exists, but your assessment of a possible timing problem seems to be the first logical one I have heard.

I will put the boat in the water this weekend and power on and off several times while observing the serpentine belt behavior to see how it is reacting and advise.

Thanks for all of your help. I can really use it.
Back to top
View user's profile Send private message
boatScotty
Senior Member


Joined: 07 Nov 2006
Posts: 229
Location: Pacific Northwest

PostPosted: Fri May 11, 2007 8:14 am    Post subject: Mercruiser 350 MAG MPI Tow Sports Sea Water Pump Impeller Reply with quote

I am willing to bet that when you shut the engine down (and try to do it as 'normal' as possible) that the belt will do that little roll back, reversing the warm, flexible impellers.

Do let me know how it goes.
_________________
Boat Scotty

Marine Tech.
Back to top
View user's profile Send private message
Captain Walker
Site Admin


Joined: 07 Nov 2006
Posts: 105

PostPosted: Fri May 11, 2007 9:14 am    Post subject: Water Pump Impeller Reply with quote

I would like to add a couple of things - it appears you are on the right track.

Make sure you 'lube' or prime the impeller when you install a new one. You can lube it with water (if you were going to fire it up soon) or with a bit of dish soap on the fins.

What type of impeller are you using? There are different compounds AND different companies make different 'mixes' for the same material, resulting in better or worse aftermarket impellers.

I also agree, the impeller is not your real problem, but I would try different manufactures impellers; and carry a spare.

Check out Sierra's parts at Go2marine

http://www.go2marine.com/productcenters/sierra/
_________________
Captain David Walker

Moderator, Boaters Line Moderator
dwalker@go2marine
Back to top
View user's profile Send private message Send e-mail
M Graves



Joined: 26 Apr 2008
Posts: 1

PostPosted: Sat Apr 26, 2008 5:00 pm    Post subject: 350 MPI Impeller Reversed Reply with quote

I just yesterday launched my boat, Merc 350 MPI and the serp belt squealed from the start.
The belt smoked due to the fiction.
I removed the belt and found the water pump would only turn one way and appeared to be the incorrect way.
I was convinced there was another problem until last night I read this thread.
Today I will confirm the water inlet is at the top of the pump which will match a clockwise rotation of the pump looking at the non drive end of the engine. (pulleys).
Basically the impeller is reversed as mentioned above. When testing the direction out of the water (short starts) I did notice the engine kicked back slightly. HAS THERE BEEN ANY INFORMATION ON THE PROBLEM AS MENTIONED WITH TIMING.

Regards
Michael
Back to top
View user's profile Send private message Send e-mail
Waterboy-787



Joined: 08 Jul 2008
Posts: 1
Location: Puerto Rico

PostPosted: Tue Jul 08, 2008 5:56 pm    Post subject: Reply with quote

I have experienced a similar problem several times with both of my Mercruiser 350 motors.

The problem usually occurs once the motors have worked hard, then switched off, and restarted while still warm. A good indicator is motor that is hard to start (I assume due to the fact the serpentine belt is frozen), and when it does start the belt "squels". I find the best fix is to loosed the adjusting pulley and manually rotate the raw water pump in the correct direction - once refitting the belt motor starts and runs fine.

Only potential cause I have found is that the belt adjustment is set to maximum and the belt may still be slightly loose. belt may have stretched but i have found a similar problem after fitting new belts. A solution may be to loosed the 2 bolts holding the raw water pump bracket and rotating it out before tightening. There is play in the pump and this allows increased tension on the belt.

Any additional experience (re timing???) would be very welcome!!!!
_________________
Amberjack 350 twin
Back to top
View user's profile Send private message
jonkidd



Joined: 25 Nov 2008
Posts: 1

PostPosted: Tue Nov 25, 2008 1:04 pm    Post subject: Inpeller removal tool Reply with quote

I'm selling a impeller removal tool.
Total price $15.00 which includes shipping to most U.S. states.
It works very well even if your boat has a ski pole in the way like mine does.
email jonstair@yahoo.com (subject line impeller tool)
I check my email's every day
Thank you
jon
Back to top
View user's profile Send private message Send e-mail
2003Hurricane



Joined: 08 Jun 2010
Posts: 1
Location: Everett wa

PostPosted: Tue Jun 08, 2010 5:26 pm    Post subject: 350mag mpi reversed impeller Reply with quote

This has happened to me a number of times... I found that actually getting two people in the back and manually pulling on the belt in the propper direction seems to turn it back, sounds weird but usually works. After the second time they replaced the impeller, saying the new one was made with better materials ect. Didn't happen for a couple of years until today. It was the first time starting it up for the year. Now even manually pulling on the belt isn't working. Going to pull the impeller and see what I can find.
Back to top
View user's profile Send private message
carmen123



Joined: 25 Mar 2011
Posts: 1

PostPosted: Fri Mar 25, 2011 10:10 pm    Post subject: Re: 350mag mpi reversed impeller Reply with quote

2003Hurricane wrote:
This has happened to me a number of times... I found that actually getting two people in the back and manually pulling on the belt in the propper direction seems to turn it back, sounds weird but usually works. After the second time they replaced the impeller, saying the new one was made with better materials ect. Didn't happen for a couple of years until today. It was the first time starting it up for the year. Now even manually pulling on the belt isn't working. Going to pull the impeller and see what I can find.


Great sharing.... Question Question Rolling Eyes waiting for new ideas
Back to top
View user's profile Send private message
buddyk



Joined: 01 Apr 2011
Posts: 1
Location: kenner la

PostPosted: Fri Apr 01, 2011 11:51 am    Post subject: Re: Mercruiser 350 MAG MPI Tow Sports Sea Water Pump Impelle Reply with quote

CC553 wrote:
Has anyone heard of an impeller (within the raw pump assembly) changing the directional rotation of the individual fins during boat operation? I have had this happen to me at least 6 times over the past year. 3 burnt up impellers and several tows later I can't explain this problem.

When symptom occurs (Not always), the boat has been turned off, the motor is hard to start, the belt begins to squeal and slip. What has happened from experience, I have found the impeller fins change direction in the pump. this causes the pump pulley to become very difficult to turn and starts smoking the serpentine belt. The only fix is to remove the pump from the motor (V-Drive Boat), remove the pump cover, pull out the impeller (Sometimes still good) and reset with the correct directional rotation. Keep in Mind Motor does not Diesel when turned off.

Local Mechanic said Boat Checked out fine on ECM555 Scanner. No apparrent problems. Could not find problem with impeller. Ironically, First trip to the lake after service, the impeller problem re-occurred right on the trialer from initial start-up. I Became angry and hit the top of the slipping belt with my fist (Very Dangerous) while motor was running. after the 2nd hit, the Sea Water Pump reversed and immediatley began to run perfect.

Your feedback will be greatly appreciated. Thanks.
Quote:


Your impellers vanes cannot reverse. That is an old wives tale. The pump is excentric and the vanes go from bent to straight exery rotation.
After one turn the blade lays back. If you set every vane backwards they flip after one turn. This old story is caused because when the motor stops, sometimes it goes backward and during a long storage they take a set with a few backwards. If at this time you open it up, you get the wrong impression. As soon you start it, they will flip. The drag on the blades pulls them back as soon it passes the area where the blades are straight.
good luck Buddy

_________________
aftermarket marine wholesale repair parts
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic     Forum Index -> Mercruiser All times are GMT - 7 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum