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Old 01-05-2013, 19:25   #1
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Impeller Outboard Fiasco!

Couple days ago, I noticed the 4.5 merc on my dink appeared to suffer from prostrate problems. It would pee, but it was more like a dribble. Damn it, its always something messing in boats. Just the other day, I fixed a leaky stuffin box, too much water, and then not enough water coming out my outboard.

I studied up on the possible causes, watched a your tube video, looked at the schematics online. Best guess was a bad impeller.

I called up to Murray Marine on Stock Island to see if they had the parts. Guy on the phone asked, " what size is the shaft?" DUH! " I dont know I replied, call ya back." Got back on the internet, searching. merc can have 2 size shafts!! Ah hell I thought, and called the dude back and asked if they had the impeller for both size shafts? Dude said he had both in stock, good I thought, see ya in a bit.

Dinked into the dink dock with my sorely pissing motor. Tied off and began the wrestling match getting the merc off the transom and onto the floating dock. Didnt do too bad, only took me a couple trys. That merc is a bit heavier than that 2hp Mariner that Rocketman loaned me. I can grab that mariner with one hand and jump onto the dock holding it above my head, no problemo!

Merc off the dink, onto the dock. Grabbed one of them shopping carts that we have at the dink dock to put the merc in and push it to my truck. Another wrestling match began. Ya know that floppy thing that tightens up to the transom...well that dern thing kept floppin around, and the tiller extension slapped me upside the head a couple times, before I got it into the shopping cart. Up to my truck did I go, and wrestles the damn thing out of the shopping cart and into the bed of my truck. Now drippin wet with sweat, I jumped into the truck and off I go.

I get to Murray Marine. I go inside and asked if it would be alright if I took the lower unit off in their parking lot, sure no problem the man said, "just dont spill any oil". "What do ya need?" I need an impeller for my I am thinking, I didnt see anything on the internet about oil coming out if I take the lower unit off...cross that bridge when I get to it.

Back out to the truck, tools out, ready to do surgery. I get the lower unit off, HA! No oil came out..nice thing that. I go back inside with the lower unit, and dude pulls out a couple impellers, slide them on the shaft, "this is the one ya need" Great! How much? 23 bucks +tax. Hmmm...ok I guess. Paid the man, and back to my truck.

Now, I pull off the impeller housing, and sure enough, a chewed up impeller inside. Did all the stuff I saw on youtube, slid off the O-rings, set aside, pulled out the old impeller, set aside, pulled out a broken impeller wing, set aside, looked for anything else in there, nothing. Good! But to make sure, I turned the lower unit upside down and tapped on the top. was that? I heard something metal hit something metal on my truckbed. Then it dawns on me....the KEY thingy. I read about the KEY thingy on the net. On hands and knees crawling around the bed of my truck looking for something, a KEY, of which I have no idea WTF it looks like. I'm just looking for something foreign, that I have never seen before, that is new to the bed of my truck. I found something, very small and shiney. A piece of metal. I looked at the shaft nearest to where the impeller sits, and I see a small flat place on the shaft, looks to be the same size as this little shiny metal piece I have in my hand. I slide it onto the flat spot, perfect fit! This must be the KEY thingy. Then I look inside the old impeller, and see a slot, same with the new impeller. So this, key thingy sits on the shaft, and the ridge on it slides into the inside of the impeller.

Now I have to figure out, how to slide all this together. As the flat part on the key sits on the flat part of the shaft, and I have to slide the new impeller down the shaft, making sure I line everything up. Couple problems here. One, the key keeps falling off the shaft. Ok, I go back inside and buy a tube of grease, 10 bucks +tax. Put a dab of grease on the Key, and stick it to the shaft. Two, I cant see the groove on the inside of the impeller when it is on the shaft. So I see which flap it sits under, and follow that line down the shaft. Problem here is, that the new impeller just doesnt slide down nicely, I have to bend over all the flaps to get it to tuck inside. But I cant bend over all of them at the same time! So one by one, I start to bend over the flaps, while turning the impeller to go inside the housing. Another problem, I forgot which flap has the groove underneath it, to slide onto the key. Zip ties! damn dont have any...back into the store for a bag of zip ties, 9 bucks +tax.

Ok, good to go now. Back out to the truck, everything in place. Use a zip tie to scrunch down the flaps. No problem now, everything slide into place. Impeller installed. Now to put the lower unit back together. Slide on the O-rings, check, grease down the top of the shaft and tranmission shaft, check, grease the studs, check, everything looks good, ready to put the lower unit back into place. Problem here is, I tried to put the drive shaft into the hole that the transmission shaft fits in....didnt realize this till the second time I tried to put the lower unit in the wrong spot and lost the upper O-ring somewhere inside the transmission shaft housing. DUH!!! I fished out the upper O-ring, after many attempts. Ok, we good, everything is back together. Feeling good about myself, I drive back to the dink dock.

I get back, and its starting to sprinkle. Battle the outboard, out of the truck, into the shopping cart, and onto the dink transom. Tighten everything up, connect the gas, and fired that muther up! WTF?? No Pee at all! Just a bunch of bubbles, and the transmission shifter is all out of whack. I cranked the motor in gear, and the dink just took off forward and bounced off the finger dock, as I scramble to flip the selector into neutral, I flipped it into reverse, and now the merc is trying to come out of the water, finally into neutral I get it. No PEE, just bubbles. Now its starting to rain for real.

Again, wrestle the merc, out of the boat, into the shopping cart, into the pickup. Now its rainy goodly. I'm getting good at this now. Took everything apart, piece by piece, slowly. Rain running down the back of my shirt, I take my shirt off, my shorts are getting wet heavy and sliding down a bit. The mississippi butt crack is imminent. With great care, I reassemble everything, struggling with putting the impeller back in, the KEY thingy again, rechecking and rechecking time and time again, till its all back together....again! Merc out of the truck, into the shoppiing cart, into the dink, onto the transom. Transmission selector is dead on this time. Reconnect the gas, a few pumps of the fuel balloon thing, a few tugs on the rope, and she fires up.....PEEING ITS ASS OFF this time. AH HELL!!! Its Katy bar the door this time!! I was grinning like a Cheshire Cat. Untied the dink, and took a ride around the bight, at high speed...its peeing! Its Peeing! and it stopped rainingy too!

What a day!!
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Old 01-05-2013, 19:38   #2
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Re: Impeller Outboard Fiasco!

I love it. Sounds like my life back when I was living in the islands. Standard joke, cruising is doing boat repair in exotic places. I started out knowing nothing at all about engines, boat maintenance, repairs and such but a few years of cruising and fixing I ended up learning how to fix a lot of boat stuff.

Now I'm not an outboard expert but I'm thinking there should be some oil in the lower unit? Might want to get out the manual or get back on the internet to check that out.
The water is always bluer on the other side of the ocean.
Sometimes it's necessary to state the obvious for the benefit of the oblivious.
Rust is the poor man's Loctite.
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Old 01-05-2013, 19:39   #3
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Re: Impeller Outboard Fiasco!

What a day indeed!


Know what you are now?

You sir, are a mercury small outboard impeller changer expert!

Wear it with pride, you earned it.
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Old 01-05-2013, 20:18   #4
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Re: Impeller Outboard Fiasco!

i realize that this suggestion doesn't apply here, seeing as how your impeller really was mangled up, but...

when an outboard stops peeing, especially in salt water, the problem is most often that the pee hole is clogged up - usually with salt. i find a paper clip is a handy tool to keep around - straighten it out and stick it up the pee hole as far as you can get it. usually gets the motor peeing again. single strand copper wire is also usually stiff enough to use.
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Old 01-05-2013, 20:23   #5
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Re: Impeller Outboard Fiasco!

Better watch out BO... one of these days yo gonna have yourself some experience, and then all of the newbies will be plaguing you with questions all bloody day long!

Good one, mate!


Jim and Ann s/v Insatiable II, lying Port Cygnet Tasmania once again.
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Old 05-05-2013, 05:13   #6
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Re: Impeller Outboard Fiasco!

Honestly, I fretted about making the repair, as with all new things thats never been attempted. I have the innate ability to really screw something up while trying to repair something. I usually break something else in the process of repairing. So with that said, thanks for the postings on this thread.
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Old 05-05-2013, 06:51   #7
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Re: Impeller Outboard Fiasco!

You still need to find out what caused the impeller to fail. Mauritz
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Old 05-05-2013, 07:35   #8
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Re: Impeller Outboard Fiasco!

A Woodruff key is what they're called (if they're flat on top and circular on the side that rests in the slot). Lots of impellers, gears, pulleys, flywheels, clutches, etc are mounted on shafts with them. 19th century invention that is still going strong.

Never seen an outboard that did not have the cooling pump impeller fail at some point in its life; reason why outboard stores always have them in stock.
The cleaner the water, the longer they'll live, but inlet filter does limited job to keep dirt out. Also, every time motor stops cooling water around still hot cylinder gets 'boiled' creating uncontrolled sticking together of microscopic particles, like sand and salt. Once an impeller starts to wear, it sorta starts eating itself, until it creates the prostate problem.
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