Scienceman Posted August 17, 2006 Share Posted August 17, 2006 A couple of months ago my battery ran flat and so recently to make sure it is still OK, the night before I go out I have just turned the motor over until it fires and let it run for ~5 sec - without attaching a hose for cooling. Is this a bad thing to do? I know motors can easily overheat but a stone cold motor run for 5 sec should be OK, or am I wrong? Link to comment Share on other sites More sharing options...
george.s Posted August 17, 2006 Share Posted August 17, 2006 bad move mate thats the best way to stuff your impeller. it only takes a sec. to hook it up to water. Link to comment Share on other sites More sharing options...
netic Posted August 17, 2006 Share Posted August 17, 2006 A couple of months ago my battery ran flat and so recently to make sure it is still OK, the night before I go out I have just turned the motor over until it fires and let it run for ~5 sec - without attaching a hose for cooling. Is this a bad thing to do? I know motors can easily overheat but a stone cold motor run for 5 sec should be OK, or am I wrong? I try to never run the motor without water, i see plenty of guys at the ramps do it without water and it probably wont do any damage to the motor but it cant be good either Link to comment Share on other sites More sharing options...
wettingaline Posted August 17, 2006 Share Posted August 17, 2006 A couple of months ago my battery ran flat and so recently to make sure it is still OK, the night before I go out I have just turned the motor over until it fires and let it run for ~5 sec - without attaching a hose for cooling. Is this a bad thing to do? I know motors can easily overheat but a stone cold motor run for 5 sec should be OK, or am I wrong? 5 secs is fine mate, as you know water is just for coolant, a motor is not going to get hot enough to need coolant in 5 secs... Link to comment Share on other sites More sharing options...
femalefisho Posted August 17, 2006 Share Posted August 17, 2006 Jim does it all the time before we put in water just to make sure it has no issues! He only switches it on then off. Done. Link to comment Share on other sites More sharing options...
caine Posted August 17, 2006 Share Posted August 17, 2006 i also start the engine while the boat is on the trailer, just for a sec nothing worse than dropping the boat in the water and realising you have a problem as you are drifting away from the ramp especialy us poor people with engines older than most fisherman Link to comment Share on other sites More sharing options...
Guest bluecod Posted August 17, 2006 Share Posted August 17, 2006 Obviously two lines of thought and as water also acts as a lubricant between the rubber impellor and the pump housing, I'd check with the manufacturer and adopt their recommendations Link to comment Share on other sites More sharing options...
Grantm Posted August 17, 2006 Share Posted August 17, 2006 The issue is not whether the engine will overheat or not because in that time it most certainly wont. The issue is as George stated being the potential to damage the waterpump impeller as there is no water in the pump. The impeller is made of rubber and spins inside a stainless steel housing and the water keeps the impeller from running dry on the housing. If it runs dry for more than a couple of moments it rapidly overheats and melts a bit. Do this all the time and you drastically reduce the life of the impeller. It may not instantly stuff it but you have unknowingly damaged it. I will admit though to cranking my motor before leaving home just to ensure there is enough battery to crank. Sometimes it fires but just for a split second. Thats enough for me. I would not recommend running it for 5 seconds, thats really damaging and reducing the life of your impeller and housing. Dry running rubber in a steel housing for 5 secongs is a loooong time in reality. Link to comment Share on other sites More sharing options...
Guest fishrunner Posted August 17, 2006 Share Posted August 17, 2006 bad move mate thats the best way to stuff your impeller. it only takes a sec. to hook it up to water. Have to agree george , I was informed early on not to start the motor without water as it acts as a lubricant for the impellor, which is only rubber usually spinning in a metal housing. This can lead to by by impellor before you know it. If you must start it before hitting the water for peace of mind, I wouldn't be applying any revs due to the increase of friction. cheers each to their own. btw My manufactures book advises to never start the motor without water Link to comment Share on other sites More sharing options...
kingpig Posted August 17, 2006 Share Posted August 17, 2006 The pump impellor is driven from the gear box. If the engine is not in gear (prop not rotating) the impellor wil not move and will not be damaged. If you crank it and let if fire then stop it before the engine had time to heat up you will cause any damage. Link to comment Share on other sites More sharing options...
wettingaline Posted August 17, 2006 Share Posted August 17, 2006 Thats exactly right kingpig..... Link to comment Share on other sites More sharing options...
inked Posted August 17, 2006 Share Posted August 17, 2006 good thread, I have often wondered about this. I was always told never to start without water, but I thought it was purely a heating thing, so therefore thought it would be ok for 5 secs. Being the mechanical juggernaut that I am, i had no idea that the impellor even existed. Can anyone else confirm that the impellor is only engaged once in gear? cheers Dave Link to comment Share on other sites More sharing options...
Grantm Posted August 17, 2006 Share Posted August 17, 2006 The pump impellor is driven from the gear box. If the engine is not in gear (prop not rotating) the impellor wil not move and will not be damaged. If you crank it and let if fire then stop it before the engine had time to heat up you will cause any damage. Totally incorrect !! The impeller is driven by the DRIVE SHAFT coming from the motor that leads to the gearbox. Havent you noticed when you are in neutral that water is coming out the telltale ? It has nothing to do with being in gear. The water pump impeller is spinning the whole time the engine is running or even turning over. Link to comment Share on other sites More sharing options...
george.s Posted August 17, 2006 Share Posted August 17, 2006 the pump is spinning as soon as you crank the the motor it doen't have to be in gear thats why you don't start it without water . the pump is fitted to the drive shaft not in the gearbox. Link to comment Share on other sites More sharing options...
Geoff Posted August 17, 2006 Share Posted August 17, 2006 Thats exactly right kingpig..... Sorry guys , wrong !!!!!!! I'm with Grantm on this one. Never start the motor with out water being supplied to the pump. Even cranking it over is questionable And yes , the impellar is rotating be it in gear or not Geoff Link to comment Share on other sites More sharing options...
Guest bluecod Posted August 18, 2006 Share Posted August 18, 2006 The impeller is driven by the DRIVE SHAFT coming from the motor that leads to the gearbox. Havent you noticed when you are in neutral that water is coming out the telltale ? It has nothing to do with being in gear. The water pump impeller is spinning the whole time the engine is running or even turning over. Right again Grant - we can only offer advice mate. Some folk aren't mechanically minded and have never pulled an outboard down to service it. Rubber residue stuck to the impellor base plate is one of the guaranteed items I find when I first service a secondhand motor I've just bought. Link to comment Share on other sites More sharing options...
kingpig Posted August 18, 2006 Share Posted August 18, 2006 Guys Sorry the impellor does turn in neutral. To early in the morning. I start mine all the time without water the day before I go fishing to check the batteries are charged and to make sure it will start. I run it for a few seconds then shut if off. This has never caused me any grief. Again sorry for the incorrent info. Cheers Link to comment Share on other sites More sharing options...
wettingaline Posted August 18, 2006 Share Posted August 18, 2006 well there you go hey....i have never had a problem with it. Thanks for the info Link to comment Share on other sites More sharing options...
netic Posted August 18, 2006 Share Posted August 18, 2006 Some great info on this thread. Outcome of the thread DONT START YOUR MOTOR WITHOUT WATER I have just check a few different websites for outboard manacfacturers and all of them say that if a motor is started without water it will more then likely void your warranty as it will do damage straight away. Link to comment Share on other sites More sharing options...
Grantm Posted August 18, 2006 Share Posted August 18, 2006 Yep i agree, it certainly has been a usefull thread, hopefully the info has helped a few people and better still saved a few waterpumps ! Link to comment Share on other sites More sharing options...
Lightweight Posted August 18, 2006 Share Posted August 18, 2006 Given the fact that there isn't water stored in the Impeller pipe, there is always a period where the impeller runs dry. Although it may be only one or two seconds, it is still dry. Sure running it out of the water is NOT GOOD, but categorically saying no running out of water may not be fact. Also, aren't the new impellers made from silicon rubber to help aid lubrication? LW Link to comment Share on other sites More sharing options...
pjbink Posted August 18, 2006 Share Posted August 18, 2006 Given the fact that there isn't water stored in the Impeller pipe, there is always a period where the impeller runs dry. Although it may be only one or two seconds, it is still dry. Sure running it out of the water is NOT GOOD, but categorically saying no running out of water may not be fact. Also, aren't the new impellers made from silicon rubber to help aid lubrication? LW I have heard that impeller damage starts to occur after 10 seconds of running without water. It is possible though damage may acumilate if you make it a habit of running it for say 5 seconds without water. So why take the risk? Always connect the water first (or imerse in water) and then start the engine. Link to comment Share on other sites More sharing options...
inked Posted August 18, 2006 Share Posted August 18, 2006 great info thanks for setting me straight! Link to comment Share on other sites More sharing options...
Grantm Posted August 19, 2006 Share Posted August 19, 2006 Given the fact that there isn't water stored in the Impeller pipe, there is always a period where the impeller runs dry. Although it may be only one or two seconds, it is still dry. Sure running it out of the water is NOT GOOD, but categorically saying no running out of water may not be fact. Also, aren't the new impellers made from silicon rubber to help aid lubrication? LW Hey Lightweight, Just to clarify that, once the leg is in the water the entire waterpump and pipe leading to the motor is completely full up to the waterline. Water will pass right through the inlet and water pump housing as the impeller does not act as a restriction. So technically once the engine is in the water the pump is full of water. Same goes for running ears, once the water is turned on it fills the pump cavity around the impeller staight away and partially fills the pipe. Yes I believe the impellers are made from a combimation rubber compound but withour water the rubber overheats very quickly. Cheers Link to comment Share on other sites More sharing options...
fisherman Posted August 20, 2006 Share Posted August 20, 2006 As a marine mechanic i see this problem all the time. As the water pump has a rubber impeller (which you all know) it needs to be cooled/lubed while rotating (while engine is running) in the stainless steel housing. If engine is ran without water the water pump impeller will not be cooled/lubed and will cause rapid wear. It is ALWAYS recomended that when running your engine, make sure your engine is connected to the hose or the lower leg of your engine (water pick up) is submersed in water. As other raiders have stated it doesn't take much to hook up the hose to your engine. I also recomend that if you want to start your engine at the ramp before launching your boat, reverse your trailer into the water, trim your engine down so the lower leg of your engine is submersed and then start your engine while your boat is still on the trailer. This will avoid drifting away after launching if your engine doesn't start. I also recomended that your water pump impeller should be replaced every 100hrs of engine running time or every 12 months. Happy Boating. Link to comment Share on other sites More sharing options...
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