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Author Topic:   Water Pump Impeller Life

skiprobinson posted 11-28-2006 02:39 PM ET (US)
[My 85-HP Yamaha outboard motor] overheated in April at the Waccamaw River Whaler Rendezvous, and subsequently I had the impeller replaced. Everything ran GREAT the rest of the season. Last week I planned to add Sta-Bil to my fuel tank and let the engine run about 20 minutes with the idea of disconnecting the fuel line and letting her run dry for the winter. I noticed that [there was no cooling system confidence stream or tell-tale] and I shut it down. I never got an overheat alarm but it bothered me and I figured I would be cautious. What to look for or check out? Yes, the ear muff's were attached and water was running. Could the impeller have worn out on only 10 hours of use?
Chuck Tribolet posted 11-28-2006 03:40 PM ET (US)
Something plugging the telltale stream?

Chuck
sosmerc posted 11-28-2006 04:00 PM ET (US)
In my opinion, it is best to replace your impeller on an annual basis, and I would wait until just prior to the beginning of your season. The water pump impeller is one of the most important components of your engine and it is subject to many stresses including both physical and chemical. Even just sitting and not moving for long periods of time is hard on impellers. And I highly recommend you use an OEM impeller.
brisboats posted 11-28-2006 05:47 PM ET (US)
Depends on use, an impeller can last several years if it isn't run through sand and silt or dry. If you want piece of mind forget the [confidence stream output] and [install] a pressure guage that you can read from your helm. First check your telltale hole for a clog. A piece of string trimmer line works great to dislodge any mud or debris.
Brian
Joe Kriz posted 11-28-2006 06:07 PM ET (US)
On the other end of the spectrum from sosmerc, I owned a 1985 Evinrude 70 hp that I never changed the water pump impeller on and I owned the motor for 15 years since it was new. I Never changed it...
This engine still had a very strong telltale stream, stronger than any engine I've ever owned. It was still going strong when I sold it a couple of years ago.
I think changing the impeller every year is overkill but to each his own.
I do however believe in putting in a new impeller if you buy a used engine or new to you boat with a used engine on it. This way you know you have a new impeller to begin with. After that, keep an eye on it through the years. If the stream looks like it is getting weak, then change the impeller, or, after so many years whatever you are comfortable with.
sosmerc posted 11-28-2006 09:44 PM ET (US)
I know what you mean Joe. I have a number of customers that have told me about their over 10-year-old engines that have never needed service and have been trouble-free. I've even owned a few trusty 3 cylinder Evinrudes and pretty much ignored their water pumps as well with no ill effects....BUT, in over 17 years in the business I have seen MANY failed impellers of all brands and this has prompted me to preach annual service as a good insurance policy against un-timely failures.
jimh posted 11-28-2006 10:22 PM ET (US)
There are many anecdotal reports of long life from a rubber impeller in an outboard motor's water pump. In my own case I am on my second season, or about 120-hours of operation with the current impeller.
It is very common for the nozzle at the output of the water cooling system aspirator (or tell-tale or confidence stream) to become clogged with debris. Usually you can just pull the rubber hose off the nozzle fitting and clean the debris from the nozzle. The cooling system may be operating properly in all other respects even if no flow is seen from the aspirator.
The aspirator helps to remove air from the cooling system, so it should be cleared and have water flow.
jimh posted 11-28-2006 10:24 PM ET (US)
Also, it is common when operating an engine on "ear-muffs" that the flow from the confidence stream will be reduced compared to the flow volume that is normally obtained when operating the engine in the water under normal conditions.
brisboats posted 11-29-2006 12:16 PM ET (US)
I do not know how long you let your motor idle on the muffs, but some motors like my mercury 150 HP V-6 will not pee until the thermostats open. I am not sure about the Yamaha in your case but older yamaha V-6's are similar. What this means is it will take a few minutes before you see water exiting the telltale, to ease those anxious moments look at the propellor hub for a fine water spray.
Or to futher ease anxiety. Remove the cowl and do the thumb test, if you cannot hold your thumb agaist the cylinder head because it is to hot shut the motor down. The therory is, if the cooling water is circulating around the water jackets as it should the cylinder head will be very warm but not so hot that you could not hold your thumb against it. Look for a smooth area near the temperature sensor on the head.
My OMC's 50-70hp will expell water from the telltale immediately upon cranking the engine.

Brian
RocketMan posted 11-29-2006 12:46 PM ET (US)
I have has a Yamaha 90 for over 20 years. My experience is that non-use is the more likely problem with this design. I've refurbished the water pump on my engine every 2-5 years.
The water pump is a vane pump configuration. It works using a symetrical neoprene bladed rotor (vanes) turning in a non-symetric cavity. As everyone knows, the pumping action is generated when the rotating blades squeeze the volume of water between relaxed blades into the smaller volume between blades displaced during rotation through the (smaller) cavity 'deformity'. This increases the pressure and creates that water flow through the engine cooling jacket.
During usage, the rotor blades flex back and forth. They ALL flex back and forth and all essentially the same number of times during a run. The energy to flex the blade during pumping is provided by the engine. But the energy to 'unflex' the blade is provided by the blade material properties. The design is such that there is no significant wear between the neoprene rotor and the smooth stainless steel cavity during usage. Also, blade flexure does not result in any significant cycle fatigue/cracking of the blades even with several hundred hours of usage.
Non-usage, however, results in a few of the blades taking a set in the displaced, flexed position. If this is more than a few months the pump performance will start to degrade and that degradation increases with rotor blade age and maybe even reduced temperature (harder to tell in Florida). This is because the blades that remained in the displaced flexed position for a long period of time no longer fully spring back, nor as fast, to the relaxed position, during usage. The result is degraded pump performance due to reduce vane performance (leakage and other crazy details).
Also, I've had the telltale stop flowing and so far it has always been due to a piece of debris that is either in the plastic discharge piece that clips to the cowl or more often right in the molded fitting on the exhaust manifold that the telltale hose clips to. The debris is usually a salt clot. I only really started having them after about 15 years or so and for a short time after I changed out the cylinder head with a new one. During that maintenance, I had to scrape out some salt deposits in some of the cooling passages and it seems you can never get everyone molecule of it out.
nanzpac posted 11-29-2006 06:20 PM ET (US)
My Mariner 100hp rarely has a stream with the muffs and my impeller is perfect and is changed anually although I might start doing it every other year becasue the impeller they take off looks the same as the new one. At any rate, the muffs just don't seem to keep the leg full of water enough to make it out the top. It drains to fast on the muffs. If the water coming out of your exhasut is warm then you know its getting up the head.
JayR posted 11-30-2006 09:21 PM ET (US)
My 1988 88 SPL Evinrude had the original impeller until 2003. Never had a problem..... Many times I sucked up sand that clogged the telltale. Fixed that by drilling it out to be large enough to pass whatever the intake screen would let in.
Interestingly enough, the replacement impeller had to be replaced after one season..... Should have left the original in there as it was still working fine.
where2 posted 11-30-2006 10:00 PM ET (US)
I'm right there with Joe. I bought my 1985 70Hp Johnson in 1996 with unknown repair history. I didn't replace the impeller for 8 years and it was still running/cooling fine. Ironically, I ran into problems with cooling immediately following the replacement. Kicked myself for weeks while I determined why it was not cooling properly, pulled the lower unit enough times that I was a pro.
I NEVER run the engine without cooling water. I carried the lower unit to my favorite mechanic, and he disassembled it right in front of me. He and I were both amazed how good the impeller looked for being over 8 years old...
I've got a 9.5 Hp evinrude in my garage that has not had the impeller changed since ~1988 (back when I was in high school!). When I used it last in 2001, it still pumped plenty of cooling water.
Your mileage may vary.
Stuff a piece of weed-eater nylon line up your cooling water outlet hose. Some insect may have packed it full of something for you.
swist posted 11-30-2006 10:25 PM ET (US)
If one does his own engine work, replacing the impeller every year might not be that big a deal, but if you have a shop pull the lower unit and do the work every year, it gets expensive. The manufacturers all seem to recommend a 2-3 year interval at worst. Why would you change it every year?
skiprobinson posted 12-01-2006 10:56 AM ET (US)
OK the saga continues....
I pulled the cowl yesterday and checked the feeder line that runs from the water outlet on the block to the cowl itself. I blew thru it and there is no obstruction. I put on the earmuffs and cranked her, yes there is a fine spray coming thru the center of the prop but only a trickle coming out of the telltale hole. Normally my motor has a strong stream immediately after start up even with earmuffs so this is unusual. I ran it at idle for 10 minutes and the block never got too hot to touch but it bugs me that the stream is so weak.
Should this bug me or should I wait till Spring when I get it tuned up anyway? I still have PLENTY to do on the boat over the winter ( secret project with pics to follow !)

advice and comments?
SIM posted 12-01-2006 11:18 AM ET (US)
Now I think I may have heard it all! In lieu of a pi$$er stream or tell tale, its now called a confidence stream.....:^) So I guess when an engine is not pumping water, we have one more thing to check.
Bad Impeller
T-stats
Poppet valve
Lack of confidence :^)

Sorry Jim......but that made my day!. Yes...OK I am easily amused.
Andy
The Judge posted 12-01-2006 12:04 PM ET (US)
No matter how long yur impeller lasts you should drop thelower unit and grease the drive shaft and mounting bolts with shaft grease(blue). I have seen many boats with 10 year old impellers that finaly fail and then the drive shaftis welded into the crank from lack of grease(usually from factory). In some cases the engine is shongo which is a shame. Happened to me with a 8 year old Merc 50. My 1999 suzuki 70 which I bought new in 2002 had a great impeller but I am glad I changed it last winter. Had to use a torch to get 2 bolts loose.
sosmerc posted 12-01-2006 03:59 PM ET (US)
The Judge just brought up a VERY IMPORTANT point. Since I am such an advocate of annual lower unit and water pump check/replacement...I had failed to mention what he emphasized....lubrication of the driveshaft splines, shift shaft splines, mounting studs, etc. If you do this on an annual basis...the job will always be a piece of cake.....but if you choose to wait until YOU DO HAVE A PROBLEM with your cooling system...well, good luck...that lower unit just might not want to come off!!
swist posted 12-01-2006 04:47 PM ET (US)
I am not suggesting that we wait until the cooling system fails, or to try to match these stories of impellers lasting 12 years - that's just dumb luck.
If you pull your lower unit every 2-3 years, replace the impeller and grease the drive shaft, shift shaft, etc, you are not going to have anything frozen solid.
brisboats posted 12-01-2006 07:01 PM ET (US)
It could be a small obstruction in the cooling system itself, water pressure drop from the last time you flushed on the muffs (city water?) different flush device. Using to much water pressure on the hose will push the muffs away from the lowerunit and result is less water being pumped by the impeller. Check to make sure the intake grates are clear and the flush device is not pushing away from them. If you can crank the water pressure from the tap and squeeze them with your hand stay clear of the prop. Try running it is a barrel if you have one or even better put her in the water one last time for a quick run.
I agree with dropping the lower at least every couple of years especially if you are using the motor in salt just top keep things from becoming permanently attached.
Brian
Bella con23 posted 12-01-2006 08:11 PM ET (US)
I finally hauled my '99 23' Conquest this past Sunday. With the boat in my driveway undergoing it's winter prep, I dropped the lower end on the '99 225 Merc. because the previous owner (my neighbor) never changed the impeller. It looked brand new as there is very little wear indicated by the manufacturing mold marks barely worn. It was replaced at least once as there is a considerable amount of silicon slopped all over the mating surfaces. Anyway I replaced it with a new impeller, gaskets, seals, etc. While draining the gear oil I noticed that there is a significant amount of steel "dust" on the plug magnet. I got to thinking about sending out a sample to a lab for "foreign matter" report. I'm a little concerned about the captured steel vs. the amount the magnet couldn't remove. Anyone ever taken this step before?
brisboats posted 12-01-2006 09:06 PM ET (US)
Bella,
That is normal and that is what the magnet is for. The silvery dust is fine when the pinion in your lower unit engages with either the forward or reverse gear there is inevitably some wear that is the "silvery dust" you see. Anything larger would also be attached to the magnet.
Brian
Bella con23 posted 12-01-2006 09:16 PM ET (US)
Thanks Brian - I have one of those nasty Rev. 4 props that bang more then I used to and it's always in the back of my head that I'll be paying the price with the lower unit one day. Not that I would ever want to change the prop., I'm having too much fun with it.
Joe
brisboats posted 12-01-2006 09:26 PM ET (US)
Joe,
If it makes you feel better those gears can make a lot of silvery dust in a lifetime, smile and enjoy the prop. Its chunks and bits attached to the magnet that would be a cause of concern.
Brian
where2 posted 12-04-2006 10:44 PM ET (US)
And then there was the time that I actually point blank asked one of the technical representatives at the Mercury booth at the Miami International Boat Show why they recommended annual replacement of the impeller. His response was that it keeps the lower unit bolts free. My reponse was "So does anti-seize compound, and I don't understand why you don't use it at the factory on those bolts...".
If I could come up with a combination of OMC Triple Guard grease and anto-seize compound, I'd have a killer product. It would be super tough to wash off... (I spent the weekend with anti-seize on my hands from working on my dock project).
jimh posted 12-05-2006 01:26 PM ET (US)
Re nomenclature: the stream of water is a confidence indicator that there is good water pressure in the cooling system. The outlet from where it flows is called the aspirator. The term "telltale" is often used. There are some other vulgar expressions as well, but they're not used here.
Binkie posted 12-07-2006 01:46 PM ET (US)
Just changed the impeller in my `87 Suzuki 150 Super Six yesterday. To make it easier to get the impeller into the housing, I slather up the impeller and the inside of the housing with hair gel. It is slippery stuff, and dissolves almost instantly when water hits it. It contains no oil or alcohol which could damage the rubber.
The Judge posted 12-11-2006 12:30 PM ET (US)
Impellers should not be too hard to get in if you twist the driveshaft while pushing it down. I sometimes use a finger dip of Dawn dish soap if one is giving me a real hard time. It washes away pretty quick as well.
wish2fish posted 12-13-2006 05:10 PM ET (US)
just wanted to clarify your orginal post. you mention that you wanted to disconnect the gas line and run dry. I understood that we shouldn't do that as one cylinder can run out of fuel (and oil) before the other and not be lubricated while the motor is still running off the other cylinders.
You added stabil so the fuel should be okay for the winter.
Food for thought!

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Author	Topic: Water Pump Impeller Life
skiprobinson	posted 11-28-2006 02:39 PM ET (US) [My 85-HP Yamaha outboard motor] overheated in April at the Waccamaw River Whaler Rendezvous, and subsequently I had the impeller replaced. Everything ran GREAT the rest of the season. Last week I planned to add Sta-Bil to my fuel tank and let the engine run about 20 minutes with the idea of disconnecting the fuel line and letting her run dry for the winter. I noticed that [there was no cooling system confidence stream or tell-tale] and I shut it down. I never got an overheat alarm but it bothered me and I figured I would be cautious. What to look for or check out? Yes, the ear muff's were attached and water was running. Could the impeller have worn out on only 10 hours of use?
Chuck Tribolet	posted 11-28-2006 03:40 PM ET (US) Something plugging the telltale stream? Chuck
sosmerc	posted 11-28-2006 04:00 PM ET (US) In my opinion, it is best to replace your impeller on an annual basis, and I would wait until just prior to the beginning of your season. The water pump impeller is one of the most important components of your engine and it is subject to many stresses including both physical and chemical. Even just sitting and not moving for long periods of time is hard on impellers. And I highly recommend you use an OEM impeller.
brisboats	posted 11-28-2006 05:47 PM ET (US) Depends on use, an impeller can last several years if it isn't run through sand and silt or dry. If you want piece of mind forget the [confidence stream output] and [install] a pressure guage that you can read from your helm. First check your telltale hole for a clog. A piece of string trimmer line works great to dislodge any mud or debris. Brian
Joe Kriz	posted 11-28-2006 06:07 PM ET (US) On the other end of the spectrum from sosmerc, I owned a 1985 Evinrude 70 hp that I never changed the water pump impeller on and I owned the motor for 15 years since it was new. I Never changed it... This engine still had a very strong telltale stream, stronger than any engine I've ever owned. It was still going strong when I sold it a couple of years ago. I think changing the impeller every year is overkill but to each his own. I do however believe in putting in a new impeller if you buy a used engine or new to you boat with a used engine on it. This way you know you have a new impeller to begin with. After that, keep an eye on it through the years. If the stream looks like it is getting weak, then change the impeller, or, after so many years whatever you are comfortable with.
sosmerc	posted 11-28-2006 09:44 PM ET (US) I know what you mean Joe. I have a number of customers that have told me about their over 10-year-old engines that have never needed service and have been trouble-free. I've even owned a few trusty 3 cylinder Evinrudes and pretty much ignored their water pumps as well with no ill effects....BUT, in over 17 years in the business I have seen MANY failed impellers of all brands and this has prompted me to preach annual service as a good insurance policy against un-timely failures.
jimh	posted 11-28-2006 10:22 PM ET (US) There are many anecdotal reports of long life from a rubber impeller in an outboard motor's water pump. In my own case I am on my second season, or about 120-hours of operation with the current impeller. It is very common for the nozzle at the output of the water cooling system aspirator (or tell-tale or confidence stream) to become clogged with debris. Usually you can just pull the rubber hose off the nozzle fitting and clean the debris from the nozzle. The cooling system may be operating properly in all other respects even if no flow is seen from the aspirator. The aspirator helps to remove air from the cooling system, so it should be cleared and have water flow.
jimh	posted 11-28-2006 10:24 PM ET (US) Also, it is common when operating an engine on "ear-muffs" that the flow from the confidence stream will be reduced compared to the flow volume that is normally obtained when operating the engine in the water under normal conditions.
brisboats	posted 11-29-2006 12:16 PM ET (US) I do not know how long you let your motor idle on the muffs, but some motors like my mercury 150 HP V-6 will not pee until the thermostats open. I am not sure about the Yamaha in your case but older yamaha V-6's are similar. What this means is it will take a few minutes before you see water exiting the telltale, to ease those anxious moments look at the propellor hub for a fine water spray. Or to futher ease anxiety. Remove the cowl and do the thumb test, if you cannot hold your thumb agaist the cylinder head because it is to hot shut the motor down. The therory is, if the cooling water is circulating around the water jackets as it should the cylinder head will be very warm but not so hot that you could not hold your thumb against it. Look for a smooth area near the temperature sensor on the head. My OMC's 50-70hp will expell water from the telltale immediately upon cranking the engine. Brian
RocketMan	posted 11-29-2006 12:46 PM ET (US) I have has a Yamaha 90 for over 20 years. My experience is that non-use is the more likely problem with this design. I've refurbished the water pump on my engine every 2-5 years. The water pump is a vane pump configuration. It works using a symetrical neoprene bladed rotor (vanes) turning in a non-symetric cavity. As everyone knows, the pumping action is generated when the rotating blades squeeze the volume of water between relaxed blades into the smaller volume between blades displaced during rotation through the (smaller) cavity 'deformity'. This increases the pressure and creates that water flow through the engine cooling jacket. During usage, the rotor blades flex back and forth. They ALL flex back and forth and all essentially the same number of times during a run. The energy to flex the blade during pumping is provided by the engine. But the energy to 'unflex' the blade is provided by the blade material properties. The design is such that there is no significant wear between the neoprene rotor and the smooth stainless steel cavity during usage. Also, blade flexure does not result in any significant cycle fatigue/cracking of the blades even with several hundred hours of usage. Non-usage, however, results in a few of the blades taking a set in the displaced, flexed position. If this is more than a few months the pump performance will start to degrade and that degradation increases with rotor blade age and maybe even reduced temperature (harder to tell in Florida). This is because the blades that remained in the displaced flexed position for a long period of time no longer fully spring back, nor as fast, to the relaxed position, during usage. The result is degraded pump performance due to reduce vane performance (leakage and other crazy details). Also, I've had the telltale stop flowing and so far it has always been due to a piece of debris that is either in the plastic discharge piece that clips to the cowl or more often right in the molded fitting on the exhaust manifold that the telltale hose clips to. The debris is usually a salt clot. I only really started having them after about 15 years or so and for a short time after I changed out the cylinder head with a new one. During that maintenance, I had to scrape out some salt deposits in some of the cooling passages and it seems you can never get everyone molecule of it out.
nanzpac	posted 11-29-2006 06:20 PM ET (US) My Mariner 100hp rarely has a stream with the muffs and my impeller is perfect and is changed anually although I might start doing it every other year becasue the impeller they take off looks the same as the new one. At any rate, the muffs just don't seem to keep the leg full of water enough to make it out the top. It drains to fast on the muffs. If the water coming out of your exhasut is warm then you know its getting up the head.
JayR	posted 11-30-2006 09:21 PM ET (US) My 1988 88 SPL Evinrude had the original impeller until 2003. Never had a problem..... Many times I sucked up sand that clogged the telltale. Fixed that by drilling it out to be large enough to pass whatever the intake screen would let in. Interestingly enough, the replacement impeller had to be replaced after one season..... Should have left the original in there as it was still working fine.
where2	posted 11-30-2006 10:00 PM ET (US) I'm right there with Joe. I bought my 1985 70Hp Johnson in 1996 with unknown repair history. I didn't replace the impeller for 8 years and it was still running/cooling fine. Ironically, I ran into problems with cooling immediately following the replacement. Kicked myself for weeks while I determined why it was not cooling properly, pulled the lower unit enough times that I was a pro. I NEVER run the engine without cooling water. I carried the lower unit to my favorite mechanic, and he disassembled it right in front of me. He and I were both amazed how good the impeller looked for being over 8 years old... I've got a 9.5 Hp evinrude in my garage that has not had the impeller changed since ~1988 (back when I was in high school!). When I used it last in 2001, it still pumped plenty of cooling water. Your mileage may vary. Stuff a piece of weed-eater nylon line up your cooling water outlet hose. Some insect may have packed it full of something for you.
swist	posted 11-30-2006 10:25 PM ET (US) If one does his own engine work, replacing the impeller every year might not be that big a deal, but if you have a shop pull the lower unit and do the work every year, it gets expensive. The manufacturers all seem to recommend a 2-3 year interval at worst. Why would you change it every year?
skiprobinson	posted 12-01-2006 10:56 AM ET (US) OK the saga continues.... I pulled the cowl yesterday and checked the feeder line that runs from the water outlet on the block to the cowl itself. I blew thru it and there is no obstruction. I put on the earmuffs and cranked her, yes there is a fine spray coming thru the center of the prop but only a trickle coming out of the telltale hole. Normally my motor has a strong stream immediately after start up even with earmuffs so this is unusual. I ran it at idle for 10 minutes and the block never got too hot to touch but it bugs me that the stream is so weak. Should this bug me or should I wait till Spring when I get it tuned up anyway? I still have PLENTY to do on the boat over the winter ( secret project with pics to follow !) advice and comments?
SIM	posted 12-01-2006 11:18 AM ET (US) Now I think I may have heard it all! In lieu of a pi$$er stream or tell tale, its now called a confidence stream.....:^) So I guess when an engine is not pumping water, we have one more thing to check. Bad Impeller T-stats Poppet valve Lack of confidence :^) Sorry Jim......but that made my day!. Yes...OK I am easily amused. Andy
The Judge	posted 12-01-2006 12:04 PM ET (US) No matter how long yur impeller lasts you should drop thelower unit and grease the drive shaft and mounting bolts with shaft grease(blue). I have seen many boats with 10 year old impellers that finaly fail and then the drive shaftis welded into the crank from lack of grease(usually from factory). In some cases the engine is shongo which is a shame. Happened to me with a 8 year old Merc 50. My 1999 suzuki 70 which I bought new in 2002 had a great impeller but I am glad I changed it last winter. Had to use a torch to get 2 bolts loose.
sosmerc	posted 12-01-2006 03:59 PM ET (US) The Judge just brought up a VERY IMPORTANT point. Since I am such an advocate of annual lower unit and water pump check/replacement...I had failed to mention what he emphasized....lubrication of the driveshaft splines, shift shaft splines, mounting studs, etc. If you do this on an annual basis...the job will always be a piece of cake.....but if you choose to wait until YOU DO HAVE A PROBLEM with your cooling system...well, good luck...that lower unit just might not want to come off!!
swist	posted 12-01-2006 04:47 PM ET (US) I am not suggesting that we wait until the cooling system fails, or to try to match these stories of impellers lasting 12 years - that's just dumb luck. If you pull your lower unit every 2-3 years, replace the impeller and grease the drive shaft, shift shaft, etc, you are not going to have anything frozen solid.
brisboats	posted 12-01-2006 07:01 PM ET (US) It could be a small obstruction in the cooling system itself, water pressure drop from the last time you flushed on the muffs (city water?) different flush device. Using to much water pressure on the hose will push the muffs away from the lowerunit and result is less water being pumped by the impeller. Check to make sure the intake grates are clear and the flush device is not pushing away from them. If you can crank the water pressure from the tap and squeeze them with your hand stay clear of the prop. Try running it is a barrel if you have one or even better put her in the water one last time for a quick run. I agree with dropping the lower at least every couple of years especially if you are using the motor in salt just top keep things from becoming permanently attached. Brian
Bella con23	posted 12-01-2006 08:11 PM ET (US) I finally hauled my '99 23' Conquest this past Sunday. With the boat in my driveway undergoing it's winter prep, I dropped the lower end on the '99 225 Merc. because the previous owner (my neighbor) never changed the impeller. It looked brand new as there is very little wear indicated by the manufacturing mold marks barely worn. It was replaced at least once as there is a considerable amount of silicon slopped all over the mating surfaces. Anyway I replaced it with a new impeller, gaskets, seals, etc. While draining the gear oil I noticed that there is a significant amount of steel "dust" on the plug magnet. I got to thinking about sending out a sample to a lab for "foreign matter" report. I'm a little concerned about the captured steel vs. the amount the magnet couldn't remove. Anyone ever taken this step before?
brisboats	posted 12-01-2006 09:06 PM ET (US) Bella, That is normal and that is what the magnet is for. The silvery dust is fine when the pinion in your lower unit engages with either the forward or reverse gear there is inevitably some wear that is the "silvery dust" you see. Anything larger would also be attached to the magnet. Brian
Bella con23	posted 12-01-2006 09:16 PM ET (US) Thanks Brian - I have one of those nasty Rev. 4 props that bang more then I used to and it's always in the back of my head that I'll be paying the price with the lower unit one day. Not that I would ever want to change the prop., I'm having too much fun with it. Joe
brisboats	posted 12-01-2006 09:26 PM ET (US) Joe, If it makes you feel better those gears can make a lot of silvery dust in a lifetime, smile and enjoy the prop. Its chunks and bits attached to the magnet that would be a cause of concern. Brian
where2	posted 12-04-2006 10:44 PM ET (US) And then there was the time that I actually point blank asked one of the technical representatives at the Mercury booth at the Miami International Boat Show why they recommended annual replacement of the impeller. His response was that it keeps the lower unit bolts free. My reponse was "So does anti-seize compound, and I don't understand why you don't use it at the factory on those bolts...". If I could come up with a combination of OMC Triple Guard grease and anto-seize compound, I'd have a killer product. It would be super tough to wash off... (I spent the weekend with anti-seize on my hands from working on my dock project).
jimh	posted 12-05-2006 01:26 PM ET (US) Re nomenclature: the stream of water is a confidence indicator that there is good water pressure in the cooling system. The outlet from where it flows is called the aspirator. The term "telltale" is often used. There are some other vulgar expressions as well, but they're not used here.
Binkie	posted 12-07-2006 01:46 PM ET (US) Just changed the impeller in my `87 Suzuki 150 Super Six yesterday. To make it easier to get the impeller into the housing, I slather up the impeller and the inside of the housing with hair gel. It is slippery stuff, and dissolves almost instantly when water hits it. It contains no oil or alcohol which could damage the rubber.
The Judge	posted 12-11-2006 12:30 PM ET (US) Impellers should not be too hard to get in if you twist the driveshaft while pushing it down. I sometimes use a finger dip of Dawn dish soap if one is giving me a real hard time. It washes away pretty quick as well.
wish2fish	posted 12-13-2006 05:10 PM ET (US) just wanted to clarify your orginal post. you mention that you wanted to disconnect the gas line and run dry. I understood that we shouldn't do that as one cylinder can run out of fuel (and oil) before the other and not be lubricated while the motor is still running off the other cylinders. You added stabil so the fuel should be okay for the winter. Food for thought!