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Discussion Starter · #1 ·
I decided it was time to tune up my motor by sharpening and shimming my impellor today. Turns out I need to probably replace a few parts and thought I would put a pictorial together for anybody who wants to attempt this themselves. I have a 115hp 1994 Yamaha.


First you need to remove the shoe off the bottom of the pump. I have already removed a couple bolts and am about to drop the shoe off



Once I removed the shoe I could inspect the wear ring that the impellor runs very close to. I found quite a few grooves wore in the wear ring. The wear ring should be flat and smooth.



Next I had to remove the impellor so I could reshim it to fit the new wear ring (which I havent got yet). I bent the tabs on the bottom washer that hold the nut on the bottom of the shaft am about to remove the nut that holds the impellor on.




After removing the bolt and the 4 washers from the bottom of the impellor I was ready to tackle the hardest part, removing the impellor. It is important to remember how many washers are on the top and bottom of the impellor, it will give you a starting point to determine where to re-assemble the parts. The impellor is cone shaped, and so is the wear ring, and by moving the washers from one side of the impellor to the other you can move the impellor up and down tightening the gap between the wear ring and impellor. I have heard several numbers of correct tolerance, but believe as close as you can get it with out rubbing is correct. I think last time I did this I ended up with a gap between the wear ring and impellor of 0.015. You can also see the corrosion between the stainless shaft and the aluminum impellor in this photo.



I had to heat the aluminum impellor to get it loose. If you apply heat, you have to be very careful to not ruin the seal above the impellor. My impellor has a plastic sleeve inside of it that partially melted when I heated the impellor trying to get it free from the shaft. It is kind of hard to pry on the impellor since it is built on a radial spiral.



After removing the impellor I found 5 washers on the top side of the impellor. You can see the seal that you dont want to melt, just above the washers which are still on the shaft in the picture.



Upon inspecting the impellor I found some massive wear on the top side of the impellor. Looks like I wont be sharpening the impellor and reinstalling. I now get to buy a new impellor. Might go with the 4 fin stainless, might go with the 3 fin aluminum. Will have to see how much of a premium the stainless one cost.



this photo shows the edge on the impellor that I intended to sharpen. It is quite dull as you can see. The sharpening is done on the top side of the fins. You follow the bevel on the previous sharpening which doesnt show in this photo.



[ 05-19-2003, 07:15 AM: Message edited by: Bait O' Eggs ]
 

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Discussion Starter · #2 ·
Next I unbolted the wear ring from the shoe. My wear ring is held in place with 4 bolts.



The last photo shows the Shoe on the left, the wear ring in the middle removed and the impellor on the right.



To reassemble is a simple reverse process. Coat everything with never seize so you can get it apart next time. It takes a couple times of jumping washers from one side to the other of the impellor to get the tollerance correct between the wear ring and impellor. And you have to reassemble the entire unit to check tolerances. :depressed: It helps to remove the grates from the bottom of the shoe so you can check the tolerance.

This impellor has about 500 hours of time on it. I changed the wear ring at about 300 hours and had none of the pitting in the impellor that I now have. The wear ring was in a lot worse condition last time I changed it. I have tried to run less sand thru the pump after seeing what the wear ring looked like last time. :rolleyes:

Off to the yamaha dealer tomorrow to see what kind of price I can get on a wear ring, plastic sleeve and impellor.

[ 05-19-2003, 07:26 AM: Message edited by: Bait O' Eggs ]
 

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WoW, looks like your pump was sucking in a bunch of air. Cavitation will kill performance and impellers. Anyway, very nice tutorial on shimming. Just for added information, "Out Board Jets" recomends a tolorance of .030 for aluminum impellers and .015 for stainless steel. For quick refrence for those who don't have gages. When shimming an impeller, remove the bottom shims and start moving them to the top of the impeller one at a time and reassmeble. Once you have moved the sufficient amount of shims, you will notice the impeller dragging on the wear ring(turn the motor over with the starter, make sure it will not start motor). After your impeller starts to drag on the wear ring, move one shim from the top stack back to the bottom. Reassemble, you impeller and wear ring should be right where you want them.

suckerfish

[ 05-18-2003, 09:34 PM: Message edited by: suckerfish ]
 

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BOE,

I have the 4 blade impeller in my 115 Merc. When the engine runs,( see as the wrench turns) it flat out leaps out of the hole. Faster than my buddies 200/21'er. My boat is an old flatbottom, which is a lot lighter than his, but the impeller is fast out of the hole and during acceleration. The boat will plane in about 1 1/2 boat lengths. Maybe less.

The downside is the thing is probably 3 MPH or so slower than the aluminum unit. A fair tradeoff if you ask me.

I know very little about pumps and such. The lifespan of the SS unit may help offset the cost. I am not sure.

Great report. Thanks for taking the time.

Mark and the dog.
 

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Great info Roy, wish I would have had it back when I had my old flatbottom with 115 merc pump. It would have saved me some time. Shimming and a little sharpening made a huge difference out of the hole.
 

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Great post. I learned all of that by trial and error when I had an outboard pump.

Looks like the salt water and sand has taken it's toll. No more sand bar hopping to get to that clam bed. :wink:
 

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Call Speciality Manufacturing/Outboard Jets for your parts. I've always bought my new stuff through them, and they've always had the cheapest price. Ask to be set up as a vendor/dealer. I did this over the phone a couple of months ago, and then you get a customer number for future reference/orders. They have a new style intake and wear ring for most motors. This makes shimming must easier and faster too.
 

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One other thing for you to think about Roy. They are now making the impellors in 4 blade aluminum. That is what came stock with the new pump we put on the 150 we traded up to on our boat after the 115 ate itself. Don't know what they cost though. I had changed to the 4 blade SS on the 115 and it did make quite a bit of difference on that motor. The SS impellor came from Woolridge boats in Seattle and cost $410 if I remember right. By the by great post!!
Good luck and tight lines, Jeff :grin: :grin:
 

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I visited Outboard Jet Mfg in Dec to pick up a part. in San Leandro Ca. They mentioned that they might be making a SS version impeller themselves.
 

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Discussion Starter · #10 ·
This has been fun today talking to east coast and mid west dealers :rolleyes: Thought I would use the internet to see if I could find a killer price on my parts :hoboy:

BOE - I am looking for a impellor and wear ring for a jet pump on my outboard

Dealer - A what?

BOE - My boat has a pump, also called a jet for propulsion. It does not have a prop. I need an impellor for the pump.

Dealer - a jet.... a pump..... Oh here I see it now, I can sell you an entire water pump impellor with O rings for the cooling system for $XX.XX.

BOE - I dont want a water pump impellor for the cooling system, I want an impellor for the drive system.

Dealer - I only have one impellor listed on the parts list and you can buy it with, or with out the O rings.

BOE - Listen very carefully,
I do not want a cooling system impellor. I want an impellor for the Jet Pump that pushes the boat to make it go, I do not have a prop on my boat, I have a Jet Pump which makes the boat go

Dealer - You dont have a prop, what makes the boat go??


BOE - The motor sucks water up and spits it out the back which drives the boat.

Dealer - Are you sure you dont want this impellor I have, because the water pump impellor sucks water up and runs it thru the motor, which cools the motor then spits it back out.

BOE - Have you ever seen or heard of a motor that doesnt have a prop?

Dealer - I have seen pictures of the boats with big fans on the back that go across the everglades, ya know like use to be on the show "Flipper".

BOE - You really have no idea what I am talking about do you?


Dealer - you seem to be confused sir, Yamaha only has one impellor and it is used for the cooling system and it does not drive the boat.

BOE - You should really look thru the literature from the manufacture and educate yourself on the options available from the manufacture.

Dealer - I have been selling parts for a long time and understand the motor inside and out, and what you are describing does not exist.

BOE - Do you have Price Albert in a Can? :wink:

Dealer - Huh???

BOE - ....click (hang up) :mad:

Looks like I will be buying the parts locally, most store east of the Rockies have never heard of a Jet Pump. :shrug:
 

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BOE,

I've got a four blade aluminum impellor off a 105 (150 powerhead) Mercury Jet that I will never use. If it would work you can have it. I switched to Stainless and don't plan on switching back. :wink:

I don't know if the 115's and the 150's use the same size impellor or not but I figured I would offer. I really have no use for it and would be happy to get rid of it.
 
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