Impeller water pump
The water pump impeller of any outboard motor has to be maintained on a regular basis, a job that when over looked can result in huge trouble. Most outboard upkeep schedules call for examination of impeller every 100 hours, or annually. And when you’ve compensated a tech to drop the gearcase and appearance during the impeller, you might and spend another $25 and acquire a new one put in. The entire task is approximately $100 of cheap insurance.
The impeller is just a number of rubberized vanes molded around a hub. The vanes are flexible, in addition to hub rotates on an eccentric inside the pump housing, that has a stainless metal lining. The ideas regarding the impeller vanes can degrade from quick use, if the engine is oftentimes run-in silty or sandy conditions, this abrasive material can accelerate impeller use. The plastic material may also get rigid and brittle, a standard issue on engines that sit unused for a couple of seasons. Then vanes can “take a group” within one place and never flex back. The other impeller-killer is temperature. Liquid lubricates the pump, incase it's operate dry the impeller may be destroyed in just seconds.
Note we stated impeller solution requires “dropping the gearcase.” For many people checking the impeller just isn't a do-it-yourself task, which can be probably the reason why many impellers are ignored until they fail.
“i do believe the most-common reason behind impeller failure we see is just old age, ” claims Dan Jansen, the lead certified Mercury technician at Mr. Marine in Fond du Lac, Wis. “Even with this brief season, I look for plenty of impellers which are too worn on tips to pump well, or are actually stiff. We make switching the impeller element of our off-season lay-up system, because if it fails you can have significantly more pricey dilemmas.”
Once the impeller fails, the pump can’t pump as well as the engine will overheat. I’ve seen old outboards that got so hot the paint burned right off the powerhead. Many more recent motors have a warning horn that sounds whenever engine gets hot, and a program that cuts engine rpm to protect the powerhead, but Jansen believes very often could be too little, too late.
“If they truly are working wide-open, by the time they notice that horn and respond, they will have a scuffed piston, especially if it is a two-stroke motor, ” stated Jansen, “ as well as if motor is OK, now they truly are out in the middle of the lake therefore the day is shot, at least.”
“You can suck countless abrasive rubbish into the pump in the event that you run the gearcase into a sand club, ” states Greenwood. “I’ve seen instances when the water intakes were just loaded to the level that water cannot also get to the pump. In the event that you be in that situation, it is a smart idea to have the impeller checked as a precaution.”
Jansen and Greenwood agree totally that beginning the engine “dry, ” this is certainly, with no water supply towards pump, is immediate death toward impeller.
“A couple of years ago Suzuki actually did a report to observe how long an impeller would last in the event that you started the engine dry, ” said Greenwood, “and it was about 20 or 30 moments.”
Jansen showed me personally a Mercury outboard water pump housing he eliminated this year this is certainly covered with melted rubber (see picture #2, above).
“The watercraft owner says he does not know what happened, but I know he started the engine inside the driveway, simply because he loves to hear that two-stroke bark, ” said Jansen. “This one got therefore hot you can observe the stainless-steel liner has in fact recessed some into the housing. Everything ended up being melting.”
Greenwood claims he’s seen ship owners whom supply the motor a fast bump aided by the starter regarding launch ramp, simply to ensure it is all set if they be in the water, among others who think they have to begin the motor after pulling the watercraft out from the liquid to drain it. Both are big errors that ruin the impeller.
“Another problem is owners think they can begin the engine if a hose pipe is installed towards the flush port, ” says Greenwood. “That pushes liquid through powerhead and exhaust, but very little reaches the pump. We tell proprietors to always use a couple of liquid muffs on the gearcase if they would you like to start the motor aided by the motorboat on a trailer.”
If an impeller fails considerably, simply installing brand new components may possibly not be the end of your difficulty.
“If the impeller really comes apart, there’s a high probability that little items of rubber can get lodged inside water tube and limit circulation into the powerhead, ” claims Greenwood. “You might observe a weak flow from water pilot out the side of the motor, and that could imply that the technician failed to look for impeller debris. If it’s uncorrected, the engine could overheat.”