Impellors- Sharpening/Shimming

[Hookset]

The boat feels a little sluggish so I checked out the impellor today. This is a 200hp Mercury jet drive with a stainless steel 4 blade impellor. The leading is edge is rounded and I could see a couple small nicks. The edge needs to be sharpened and maybe the impellor shimmed.

For those that have done this. Is the process hard and how can you sharpen a stainless impellor? What about front eedge angle, I was told this can really make or break the performance. How do you determine when and how much to shim? What tools and parts do I need to complete this?

I'm sure you get the general idea behind this post. I need some help and really need to improve the performance.

Thanks, hook

[Bait O' Eggs]

Hook, I did this to my boat a while back, I have an aluminum impellor and a Yamaha but it shouldnt be to different

Pulling the shoe is quite easy, I had about 8 bolts or so on a ring. The sleeve the impellor runs against will come off with the shoe. This needs to be pretty smooth. Mine had been completely eaten. I could lay a quarter in a couple different spots that had been eaten out and the impellor would not hit it. Guess I should run less sand thru the pump. [img]images/icons/rolleyes.gif[/img]

I had a big nut to pull off the bottom of the impellor. There will be several washers between the nut and impellor. count how many you have at this spot. Pulling the impellor was a hemorroid (pain in the a$$). An aluminum impellor and a stainless shaft created some nasty corrosion that didnt want to let go. I would bet that since you have a stainless impellor it should come off easy. I had to heat my impellor up to get it loose from the shaft. You cannot get it to hot or you will ruin the seal on the shaft above the impellor. There was a plastic sleeve inside the impellor that I did melt though.

Once I got the impellor off, I dont remember what angle I tried to maintain, but it was pretty obvious what the existing angle was and I just tried to match it, with a file.

I think I had 5 washers below the impellor and 2 above on my motor. When I put it back together with the new sleeves (one plastic one inside the impellor and a new metal one in the shoe) and the same washer configuration I had a 0.035 gap between the impellor and outer sleeve. Terry at South river marine told me to get it as tight as I could, he liked to get about a 0.020 gap, with no rubbing if I remember correctly.

I took it back apart and moved one washers from the bottom of the impellor to above it. I was then at about 0.27 or so. So I jumped a couple more washers and was at 0.015. This is when I tightened it up and called it good. My performance was night and day difference.

To make measuring the gap easier I pulled the steel grates from the shoe so I could get my feeler gauge up to the impellor. I also sharpened the bottom edge of the steel grate kind of like a knife so I could get water into the shoe easier. There are a couple other things that you can do to trick out a shoe for better performance. They didnt sound easy and I just went with the sharpend grate.

I know you said your boat didnt perform very well on the floatilla. One thing you might check is that you have the right impellor on your motor. My dad went with a 4 fin stainless from a 3 fin aluminum. His boat was a big dog after doing this. As he told me, they sold him the impellor for a 200 hp Yamaha when he had a 115. When he finally got the right impellor in the motor, it performed much better. I would think a 200hp impellor would not fit in a 115 but I guess it did.

Good luck,

[willierower]

hookset,
Tom,s Outboard can tell you the angle that needs to be on the impeller. The # is 503-63-8744.
Shimming the impeller is fairly easy. BOE pretty much explained it.
One thing you should do when you have the shoe off the pump is, Sharpen the the grate pieces. Sharpen them on both edges, top and bottom.
There is a whole bunch of things you can do to the shoe to increase performance. You need access to a lot a machineing tools to do it. Tom Sperb can tell you what to do.

[Thumper]

I have to disagree with BOE on one point. I sharpened the intake grate edges on my old 200 too and cursed doing that for the rest of my time with that motor. When the plates are left alone; i.e., square-edged, they may pick up small rocks and sticks but when the motor is turned off those obstructions generally fall away, leaving the grate clean. When you sharpen the grate edges they pick up the same junk but it gets wedged into the grate (natch!). Then when you turn off the motor the junk stays stuck. It doesn't fall away. You then get to pry that crap loose with a screwdriver every time you run in shallow water. Never sharpen those grate edges. They are flat-edged for a purpose.

[Bait O' Eggs]

Thumper that concern did cross my mind, I figured I could jsut flip them upside down if it was a problem. So far nothing stuck in the grate, been about 3 months.

[FishinMission]

I just had my impeller shimmed...the guys at Stevens say .010 is the fit you want. Bait...you got it close enough for me. That ain't much room. They'll do it for you for a hundred bucks. If you go this route...you can speed up the turnaround time by removing your pump and takling just the pump in for the work. Steven's needs to book appointments based on boat storage. They told me about 2 weeks out if I bring the boat. I took the pump off...and had it back the very next day. As for the performance....the correct shim will be more important than the sharpening...but since you got the impeller out... I'd sharpen it.

[blackdog]

What about sharpening the prop on a kicker? I have an 8 horse Merc that I've been running on my driftboat for over ten years and the props edges are way less than sharp. Can I just get out a metal file and go at it until they are sharp and clean or is there anything specific I should look for? I appreciat the help.

[Thumper]

Sharpening the impeller edges is a no-brainer. I say that because I can do it, and I have a hard time tying my shoes. You just remember that the idea with an impeller is to draw water in. So you sharpen only the upper edge, only very lightly touching the lower edge just to remove burrs once the upper edge is done. The lower edge should be flat. One of our members (Fin) has a 75 HP Merc on his little 16 ft. Guide Model Alumaweld that has never had its impeller sharpened, and he got the motor in 1985 or so. It runs and performs great after all these years. Sharpening isn't needed very often, and almost never is needed on the stainless upgrade.

[boater]

hook, the impeller is easy to sharpen, just file to the same angle thats on it and you will have no probs, it`s kinda like a lawnmower blade, sharpen on the top and never on the bottom. i went to autoparts store and picked up some extra long feeler guage blades, they are about a foot long so you can stick them thru the grate prety easy and check the clearance. also i found out the liner in the pump will wear even if you dont suck anything thru it, the water burns it and eats material away. also you should talk to other owners of the same setup you have and see if there max. rpm is the same as you, if yours is high you probly have the wrong impeller. just my 2 cents of bs..

[Hookset]

Thanks everyone for the help. Haven't had the pump off and never took one apart yet. Sounds like the first thing is to check the clearance of the impeller from the sleeve. Just looking at it, looks alot wider then .015, more like .060. Is the sleeve tapered from end to end? If I take it apart, it'll probably be self explanatory.

Willierower, where is Tom's outboard? In Lebanon? The phone number you provided is missing one number.

Hey bait, when you were down here, I should of had you stop over to help shim/file this impeller. Sounds simple enough.

FM, what rpm's are you running with your 200hp and what is your top miles per hour? I'm running 34 mph at 4900rpm with just me. Not great and certainly not what I get with a load of people.

thanks,

hook

[FishinMission]

Hook..Tom's is on Mcloughlin...just south of Milwaukie, and right across from the "Bomber". Well...I'd say my top speed with my old 200 and the new impeller was right around 38-40 mph...@5000 rpm.(20 foot flat bootom Fish Rite barge)with just me in the boat...but upon dis-assembly of my 200 I found a couple of cylinders that had no wear on them (I could still see the hone marks from 10 years ago) so I have to believe I had a couple of cylinders with lower compression that I'm sure affected my performance. Good news here tho is that the wifey agreed last Sunday to "cave" and we went and bought a new 200 Merc. Supposed to get it "hung" on the boat next week. Woo hoo!!!! And no...I didn't get the "new" jet...we bought a new 2000 model as close-out from Stevens. I just dumped $800.00 into my old pump...and would pretty much eat that $800.00 if I bought the new 200 Jet. Instead I'm into this new motor for about $2500.00 less than the newer model jet. I suppose I can live without that extra 10 mph. for $2500.00.

[ 06-05-2001: Message edited by: FishinMission ]

[ 06-05-2001: Message edited by: FishinMission ]

[willierower]

hookset,
here is the # again
503-653-8744
503-680-1036
Theses are the #'s on his buisness card. My friend gave me the card. He was up there last friday and Tom told him all the little tricks to do to his pump.

[Jim]

I definitely would have someone sharpen my SS impeller!! The sharper the better! With SS you should be able to shave with it...

Mission...you are exactly right...I have a 21' Thor and with me in the boat we go about 52...the nice thing though...is that with 4 more adult males we go about 48...don't lose much...any nice to have a new motor on the back end...just feels good!

Jim

[FishinMission]

Uh huh...I have to wipe the drool off my keyboard!! [img]images/icons/grin.gif[/img]

[FishinMission]

Hook...if you shim your impeller yourself...don't forget to get the little plastic sleeve that fits between your shaft and impeller. I got mine at Steven's, but anybody that works on pumps should have them. The idea behind them is that you heat your impeller enough to melt the plastic sleeve that's there now, then your impeller should slide off. You'll need to replace it though when you put it back on. Very important!! also...look at the cup to see if it's worn or has grooves in it. You may need to replace it too if it's grooved or worn. That'll run you about $40 bucks...again...available at Steven's, and usually in stock. Good luck!!

[Lives_to_fish]

Question,
Can the shimming be avoided by replacing the cone? Is the depth and diameter of the cone precision enough that if you replace it, the clearance will be correct, or is it one of those things that when you install a new cone, you just plan on adjusting the shim pack?

Thanks,

LTF

[Bait O' Eggs]

Lives to fish - All I can tell you is from my one time experience. I replaced the outer sleeve and the impellor was not tight when I put it back in the same spot. This makes sense, because as the sleeve wears I can only assume the impellor wears also. Gotta keep that tolerance close so you dont lose water around the outside of the impellor.

[LAYthe5]

be careful when filing on impeller's and watch out for ding's. These both can take the balance out of your impeller and wear on your main shaft bearings. Seek a professional, and they will most likely check the balance too.

LTF