Idea for preventing over Winter Impeller set

[Scaaty]

I got too many lower units with impellers. I can't be dropping LU/s every spring. That said, my newly crank up 72 135 Merc Stack (less than 10 hours) has those smaller thick impellers that take a set too easy. The whole boat/motor covered, so too much work to hand crank the Flywheel ever month. After starring at it while downing a 6 pack yesterday, the flash hit about beer #5. I uncovered it, loosened all the plugs, put it reverse (it won't work in forward, the ratchet thing), and made sure it wasn't too hard to hand turn the FW. The propshaft turned in reverse. I then stuck the prop on, hand cranked it a touch in reverse. Got the FW to turn about 1/3, so now any compressed blades have moved, replaced with another few. Wrapped it all back up. My plan is go out once a month and give it a slight rotation with the prop (in REVERSE OF COURSE..that a pretty important reminder..go forward, the impeller wil be going the wrong direction and will be junk soon of course)
Thoughts?...or to much beer?

 

[jetwhine]

Re: Idea for preventing over Winter Impeller set

Hey Scaaty,
Now that sounds like a good idea, but if the impeller gets stiff over time dont you think that when started after a winter and run in the forward direction for the first time that it would be even worse for the imperller when forced to bend back in the forward direction? It seems to me that someone should have come up with a modification with a metal imperller that would not have these issues? Just a thought after seeing what mine looked like when I pulled the lower unit. There must be a rubber out there that would hold up to this abuse. To me why did they make an imperller out of rubber in the first place. With my years as a jet mech Ive only seen metal impellers. They work great.
Jet.

 

[Scaaty]

Re: Idea for preventing over Winter Impeller set

Hey Scaaty,
Now that sounds like a good idea, but if the impeller gets stiff over time dont you think that when started after a winter and run in the forward direction for the first time that it would be even worse for the imperller when forced to bend back in the forward direction? It seems to me that someone should have come up with a modification with a metal imperller that would not have these issues? Just a thought after seeing what mine looked like when I pulled the lower unit. There must be a rubber out there that would hold up to this abuse. To me why did they make an imperller out of rubber in the first place. With my years as a jet mech Ive only seen metal impellers. They work great.
Jet.

Your lost here..the impeller turns THE SAME WAY ALWAYS..NEVER...NEVER..NEVER in reverse. The prop shaft is in reverse position, and turning the prop in reverse also, turns the powerhead and impeller the same as always rotation (reverse is in the gearcase, not the driveshaft)...can you visualize what Im saying.? Its can't be done in forward, as the prop will just ratchet.

That said...why the hell we still use rubber impellers is WAY beyond me...seems a SS Gearotor (sp)... (like an oil pump or similar more intelligent design..must be a reason, maybe someone has the reason...

 

[hkeiner]

Re: Idea for preventing over Winter Impeller set

Thoughts?...or to much beer?

My vote is for "too much beer."

 

[Scaaty]

Re: Idea for preventing over Winter Impeller set

My vote is for "too much beer."

Can you elaborate "why"...(not the beer, the idea..which is a known fact on the hard, small, stiff rubber impellers)

 

[hkeiner]

Re: Idea for preventing over Winter Impeller set

Sorry Scaaty, my comment was an attempt at humor.

 

[JCF350]

Re: Idea for preventing over Winter Impeller set

Has far as why rubber impellers goes is that when the engine is at low RPM's the blades ride against the housing making it a displacement pump, at higher RPM's the blades fold a little bit and do not contact the housing making it centrifugal pump.

A displacement pump moves more water at low speeds than a centrifugal and vice versa at higher speeds.

Now has far as the "taking a set" issue goes I ain't got clue cause it don't get cold down here.

 

[jetwhine]

Re: Idea for preventing over Winter Impeller set

Scaaty,
Yes I can visualize what you are saying. Dont know what I was thinking when I said that. Maybe I had too many beers. It is just like any tranny. The bottom line is they need to be made out of stainless steel. As far as the rubber goes, I'm with you , does anyone know why the impellers are made out of rubber?
You never know what those engineers are thinking.

 

[jetwhine]

Re: Idea for preventing over Winter Impeller set

Scaaty,
Yes I can visualize what you are saying. Dont know what I was thinking when I said that. Maybe I had too many beers. It is just like any tranny. The bottom line is they need to be made out of stainless steel. As far as the rubber goes, I'm with you , does anyone know why the impellers are made out of rubber?
You never know what those engineers are thinking.

 

[JCF350]

Re: Idea for preventing over Winter Impeller set

Scaaty,
Yes I can visualize what you are saying. Dont know what I was thinking when I said that. Maybe I had too many beers. It is just like any tranny. The bottom line is they need to be made out of stainless steel. As far as the rubber goes, I'm with you , does anyone know why the impellers are made out of rubber?
You never know what those engineers are thinking.

see the post before yours

 

[ThumbPkr]

Re: Idea for preventing over Winter Impeller set

I think that rubber can handle the occasional ingestion of sediment a lot better than a pump designed to use metal impellers could do,like an oil pump in an engine for example.The water pump in our outboards is designed to exploit the qualities of rubber,its flexibility.A metal impeller could not work in our water pumps as they are designed.
I think the current design is an engineering marvel with the most cost effective tradeoffs all being considered.Ron G

 

[Laddies]

Re: Idea for preventing over Winter Impeller set

Robby, lets load her up and head some where warm, it's 28 degrees here -- Bob

 

[MercGuy]

Re: Idea for preventing over Winter Impeller set

I don't want this to sound sarcastic, but is Impeller set really a problem ?

I've owned 4 outboards since the mid 1980's, and in all that time I've replaced 2. Mainly out of guilt, and found nothing wrong with the ones that I've pulled out.

I don't know of any friends that have ever had problems with impeller set, and I really don't remember reading about it on this board before.

I live in Cincinnati, so it does get cold here during the winter.

Just wondering why you think it's a problem...

Cheers !!

 

[SeaKaye12]

Re: Idea for preventing over Winter Impeller set

I have a 1977 Merc 850 that sat un-used for over 20 years. After re-doing the internal wiring harness I fired it up on the muffs. It pee'd such a strong stream that I ran it for one season before finally looking at the impeller. It was a little hard (compared to the new one) but was in pretty fine shape overall.

I wouldn't think that one year's storage is going to cause much trouble either....but it's not much of a job to replace one. Less work perhaps than trying to figure out how to prevent "set"?

Chuck

 

[Silvertip]

Re: Idea for preventing over Winter Impeller set

I have a hunch that metal impellers aren't used because of the debris that must pass through the pumps. However small that debris may be, it would likely raise havoc with a metal pump. Water also makes a fairly good lubricant for rubber but I doubt it would work well lubricating metal. Rubber doesn't rust like a metal impeller would, unless it was made of stainless steel and that increases cost significantly. Then there is the salt water issue. Just for the record a couple years ago I bought 1998 75 HP Merc with extremely low hours. Since I didn't know how long the unit had sat unused, I replaced the impeller. The impeller fins came out of the housing straight as the brand new one and with nary a mark on it. I really feel storage does not harm them. Besides, a little centrifugal force when the engine is running straightens them out. Is it necessary to replace them frequently, certainly, but unless you are putting hundreds of hours on the engine in a season, certainly not annually. On a recreational boat getting 40 - 50 hours a season, I feel three years is just fine -- unless of course one runs through a mud flat, sand bar, or is constantly in silty water.

 

[j_martin]

Re: Idea for preventing over Winter Impeller set

I hit a mossy chit weed peat bog spot dropping off plane unexpectedly in shallow water. Plugged up the intake ports. I freed them and the water pressure was then low. especially at idle.

It had plugged or jammed both thermostats, the poppit valve, and a few of the small water passages in the exhaust cabinet. Fixed all that, ran it before going after the pump, and it was fine, didn't need an impellor.

I think if you are in the North and have to fog down the engine for storage, you normally run it on the muffs in the spring to clear all the oil out and find out if you have to change out any fouled plugs before you launch it. If the water pressure is good, yer good to go. If not, now's the time to drop the LU and throw in an impellor kit, or a complete pump depending on how deep into the sand you've been.

hope it helps
John

 

[gss036]

Re: Idea for preventing over Winter Impeller set

I think a water pressure guage would be a better investment. I changed my 15 hp Honda's impeller the first time last year, it had been there since 1993 and has 3 to 4 thousand hours on it at trolling speeds. It still worked but was showing signs of low pressure pee stream.

 

[Scaaty]

Re: Idea for preventing over Winter Impeller set

Sorry Scaaty, my comment was an attempt at humor.

(didn't think there is such a thing as too much..too LITTLE..now we got a prob!

 

[Scaaty]

Re: Idea for preventing over Winter Impeller set

Has far as why rubber impellers goes is that when the engine is at low RPM's the blades ride against the housing making it a displacement pump, at higher RPM's the blades fold a little bit and do not contact the housing making it centrifugal pump.

A displacement pump moves more water at low speeds than a centrifugal and vice versa at higher speeds.

Now has far as the "taking a set" issue goes I ain't got clue cause it don't get cold down here.

Excellent post! Its not really a temp issue, its just that the fins are really bent over at one spot, and can take a set (mostly with age, but thats a replace anyway thing).
I have a 125 Force that the pump was replaced probably 6 years ago, maybe more...pumps fine. I don't worry about the small kickers, ..they spit, they get wet. They stop, drop'em.
My 350 engine raw pump at one time had a 6 fin hard/thick impeller. Salt finally got to the bushing. Picked up a new Sherwood"Jabsco, and this is a 12 fin, thinner blades. Much more flexible.
This is a new rebuild, and I'm just a little too picky and paranoid of my motors (this motor last year at this time was just a crankshaft laying on a bench, I built the boat, Merc Guru did the motor....ya should see the look I got when I said its good for a few years (impeller). Thats his baby, and if I don't treat it right, he will come and take my keys away! I'll probably drop it in the spring anyway, as it does hit salt, and I simple want those bolts out nice and easy, plus keep an eye on the shaft under the pump for corrosion that will trash a DS seal. Plus its like my old Harleys...I don't care if I never start them...just fun to look at and twirl a wrench on'em.
Good posts/comments..thanks..
PS. Bob..can't help ya on th 28 temp 'cept wait for the snow, and get those Sleds out..I still miss those sunny cold winters days snowmobiling in the Northwoods, bar hopping with a bunch of crazies!

 

[j_martin]

Re: Idea for preventing over Winter Impeller set

When my OB degrades to the reliability of an old Harley, it's going down the road.

I like to wrench on my own stuff, but I like to use it more.

John