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Hello Brooks89 and yes I properly referenced the impeller vein collapse direction.
When I remounted the lower unit the spline engagement was slightly off, so I had to further rotate the input shaft. It rotated without effort and in the direction of the vein collapse.
I've got to say, Angel, those photos seem to show the impeller melted to the housing from a lack of water.
I winter in Ft. Myers and summer in St. Joseph, Michigan. It’s now about 12 years since I’ve joined this group. I gave my 1972 whaler to my daughter and sold the 17’. Bought an O’Day 28 sailboat and sailed on Lake Michigan. Yesterday I bought a 2005 130 Sport.
Hello Wing15601, it would appear that way from the pictures if no explaination was offered.
Repeating from my initial post, the outboard was ran for approximately 10 to 15 minutes (not continuosly) on two separate occassions roughly a week or so apart and without incident. Initial start-up after re-installing lower unit (impeller rebuild) with motor run on "ear muffs". Second start-up as described above (time and date wise) was done with 40 gallon flush bag and steady fresh water supply and again no incident. The "tale-tale" produced a steady uninterupted stream with each event with the exception of last Sunday (third start-up and a month after last run cycle).
Al who posted previously and recounts his personal outboard repair experiences feels that my description of how the impeller went onto the input shaft may be the smoking gun. I would be the first to admit and wouldn't have bothered posting to W/C if it would have been a situation of failing to supply water to the outboard.
This isn't my first powerboat and I am quite capable of doing most major repairs and maintanence as long as information (shop manuals) or "factory how to secrets" are available. No where on the web does anyone really detail how the impeller is suppose to press/fit onto the input/drive shaft, "my bad" with this incident.
Angel, it sounds like you did all the right things. I agree with wing15601 that at some point, water was absent and the heat buildup caused the impeller to self destruct. While part of this may have been caused by an impeller that was too tight on the shaft, I am now wondering why the stainless cup rotated in the plastic impeller housing. While I am not familiar with the Yamaha configuration, most similar pumps prevent the cup from rotating by a tab or bent circumference to keep the cup in place. Is it possible that the cup rotated, blocked off the discharge port (thereby shutting down the pump's ability to move water) and once the pump was no longer pumping, the impeller failed?? I would not expect even a dry pump to be able to rotate the stainless cup. A dry pump would certainly cause the loss of impeller vanes, but the cup should remain in place and not rotate even under that scenario.
I recommend you go back to the basics when you reinstall. Check to make sure the intake is clear from the screens up to the pump. Check to make sure the engine passages are clear of any debris. Check to make sure you have the correct parts. Double check the vane direction (if engine rotates clockwise when viewed from above, you must either rotate the shaft clockwise or the impeller housing counter-clockwise). Check the anti-rotation features of the stainless housing cup and insure it is seated when you install the pump housing.
Sure wish I was close by to help, and hope the next installation goes without any problems.
I was refreshing my memory on the impeller replacement and searched Youtube. I see one for a 1990 50hp Yamaha and after viewing it, it got me thinking:
Were you able to get the wooddrif key out of the shaft?
Did the new impeller line up with the key?
While it does not show these steps, take a look at the video and see if you might see a cause for the failure. Note, I personally disagree with the author about not changing the wear plate and o-rings.
Hello again Al, yes the stainless cup has a formed/stamped tab for locating within the upper housing. As wing discussed and I will agree, at some point the pump unit failed to draw any water thus the over-heat and failure condition that followed.
The question is when, either soon after the outboard was shut down from 2nd run cycle over a month ago or as I attempted to start it this past Sunday??? Inquiring minds may never really know...LoL.
As you suggested Al, I have already checked water passages and flow through powerhead by back-flushing from thermostat block cavity and by also flushing with block flush port. I checked for any debris through cooling system before and during flush, none present. Exiting water flow was good through "tale-tale", block flush port, and brass up-feed tube. Water passage in lower unit have been thoroughly picked clean and flushed. Strangely enough the broken impeller veins accumulated just behind the plastic inlet screen/baffle of the lower unit.
Phil, thank you for the web link. I viewed this video and various others prior to the rebuild. Unfortunately the water pump assembly in the video is a bit different than on my 2007 Yamaha 90. The only 2 components that appear similar is the impeller and the plastic upper housing (but only in appearance). My upper housing does not use an o-ring for sealing, it utilizes a gasket and there is no o-ring used under my impeller assembly. I replaced the original wood-ruff key with a new unit from the rebuild kit. It is currently intact and with no visible damage. I may elect to re-use it.
I will certainly check and re-check every step of this second rebuild and I will mic the shaft diameter to compare with new impeller I.D. during purchase for irregularities.
Thanks to all who posted and for the suggestions...I will update after second rebuild and start-up.
Although I am unable to add anything more constructive than what has already been expressed by previous posters I am compelled to ask if other brands of outboard have a different and SUPERIOR water pump design.
Though few on this thread could be as inexperienced as I, the impeller replacement was easy....once I could get the lower unit off (1991 Yamaha 40hp).
My biggest gripe with the Yamaha design is the correct seating of the uptake tube (why not longer with a positive connection for something so crucial) and the absence of a mesh filter to prevent debris from clogging the water circulation channels in the upper block.....I am told this will kill the engine.
BTW, NOTE TO SELF: next impeller replacement, buy two impellers....one complete kit and one extra impeller.......it's cheap and reduces the stress of fiddling with a greasy impeller and sharp housing cup.
Hello docsoma, after discovering the amount of salt contamination or crusting within the thermostat environment, I can only imagine what the unseen water passages might look like.
I have flushed as much as I can for now with lower unit having been removed but, I feel that (and also depending on salt water usage of vessel/motor) a chemical flush might be a good option a couple of time during the boating season. Products such as "Salt Away" and similiar and even a "Simple Green" degreaser mix with motor water flush with an appropriate dilution rate of course (10 to 1 ) ratio has been discussed on a few forums.
This was one reason why I purchased the outboard flush bag that I have mentioned during this thread.
I do not feel the pump/impeller assembly design is flawed, infact your's is much simpler than mine. My 2007 Yamaha 90 TLR 2-stroke uses more components than your 50, the issue is that there really isn't sufficient information available for the smaller assembly details. I purchased an official Yamaha manual almost specific to my motor and there is no details to impeller fittment concerns.
We live an learn I guess, I'm just really glad that I never had the opportunity to water test the boat since remounting the lower unit over a month ago. I may have certainly ruined the power head with the failure because the water test would have been intended to check for a "safe-mode" condition that presented itself back in August of last year and which I had posted a discussion thread on.
The August incident eventually uncovered (and after much testing and investigation by me and a boat repair center) that a water pressure/flow problem was developing, thus the cooling circuit overhaul. I would have never imagined this type of failure and at a W.O.T. condition. OUCH!!!
Rebuilt the impeller assembly this afternoon with all new parts from a local boat shop/Yamaha dealer.
I showed them the damaged parts and detailed the trouble I had with the impeller fitment.
The parts guy and one of the mechanics present were quite surprised with the damage. The mechanic's opinion is that the impeller sat high in it's location causing excessive friction with the stainless cup leading to the eventual failure.
The mechanic explained that the Yamaha 90 2 stroke impellers have a tendency to fit somewhat tight but not to the point that they most be forced into place as I had to. He recommends always lapping the shaft area with mild grit emory cloth/sandpaper to dress the diameter prior to install. Then a mild coating of grease or as he mentioned a good lubricant/penetrant such as "Corrosion X" to ease in sliding the impeller.
I mic'ed the shaft diameter before heading to the Yamaha dealer and measured the new impeller I.D. while there. The clearance diameter was good, I did a test fit once home and the new impeller fit perfectly into position and easily removable as well.
The input/drive shaft must be turned "clock-wise" to properly set the curve of the impeller veins which I did when setting the upper housing into place followed with tightening the 4 bolts down to 60 in. lbs.
Thermostat asembly is re-installed and I hope to start the outboard sometime tomorrow. I did encounter one hiccup during the lowerunit assembly the 8mm x 1.25 bolt that goes through the trim anode area up into the mid-section, during the torque sequence failed or fatigued when my torque wrench failed to register the appropriate setting. A bit of drilling and extracting and all is well again along with a newly purchased and installed bolt.
I will post the start up results, till then...
Angel M.
Wanted to update those that followed my impeller failure thread from a few days ago. I mentioned in a post Thursday evening that I had completed the second water pump rebuild. I started the Yamaha 90 yesterday afternoon with excellent results. I ran the motor in the 40 gallon flush bag and before start up I primed the cooling system through the block flush port for added measure.
I ran the motor intermittenly for 5 minutes with excellent water flow from the "tale-tale". Today I water tested the Dauntless. Through a good friend I was granted access to a substantially sized residential fresh water lake system in my immediate area.
I put the outboard through numerous (get on plane) W.O.T. scenerios with excellent results. From the numerous test runs I did today I can say that I have corrected two major issues that were plaguing my outboard.
The first was the original condition from August 2013 the "safe-mode" operation that could not be properly diagnosed even after various attempts. Eventually the culprit was the cooling circuit thus the complete water pump, thermostat assemblies, and temp sensor replacement. The lastest issue with the impeller failure which is now resolved has greatly educated me with impeller design and fitment.
I was also able to test (the new to me) "semi-cleaver" prop I had purchased some months back. Incredible stern lifting capabilities from this prop, the Dauntless jumps right on plane immediately with no effort or stuffing the stern.
The wife and I can't wait to get back out on the bay again and head to our favorite sand bars in the Biscayne National Park area's. Thanks again to all that follow and offered suggestion to my impeller thread.
Happy boating and Memorial Day holiday to all our Military families and friends still in harm's way.
