Signs Of Impellor Needing To Be Changed

[nsaykali]

just a quick question,

i have a 2003 tohatsu tldi 50hp outboard on my boat.

a few months back i realised that when my boat was in neutral or on very low idle, the water stream was not continious and was dribbeling, causing the motor to run hotter than normal, causing the heating alarm to go off, but once i manually raise the idle leaver in neutural or when i put the motor into gear and drive at revs higher than idle, the water stream coming out of the motor is continious and strong.

after a few outings, this stopped happening and in idle the water would come out continiously, untill this weekend, same thing started happening, in neutural dribble dribble, but when driving and revs up, the water would come out with no issues.

is this an sign that the impellor needs changing?

thanks in advance!

[chrisg]

Change anyway. With any cooling issues always start at the beating heart of the system...the pump. A new impeller and gaskets at a minimum. At least then you'll know it's not the pump and can investigate further eg sticky thermostat.

C.

[Kosta1]

You might want to check where the water comes out, i had a problem similar to yours. A little stick got caught where the water exits the motor. I just got a pin and removed it. A thin piece of wire will do the job aswell.

Even if it isnt blocked you should change the pump just to make sure.

Cheers

Edited December 14, 2010 by Kosta1

[brickman]

you should change the impella every 12 months regardless off usage if the impella starts to rot and brake up you could block up the cooling galerys and then the motor could be stuffed in a very short time

this happened to my first boat it had a salt water aspren on it

cheers gary

[musty]

just a quick question,

i have a 2003 tohatsu tldi 50hp outboard on my boat.

a few months back i realised that when my boat was in neutral or on very low idle, the water stream was not continious and was dribbeling, causing the motor to run hotter than normal, causing the heating alarm to go off, but once i manually raise the idle leaver in neutural or when i put the motor into gear and drive at revs higher than idle, the water stream coming out of the motor is continious and strong.

after a few outings, this stopped happening and in idle the water would come out continiously, untill this weekend, same thing started happening, in neutural dribble dribble, but when driving and revs up, the water would come out with no issues.

is this an sign that the impellor needs changing?

thanks in advance!

I have the same thing happen with my Mercury. I dont know about yours but on my Merc thats what is MEANT to happen. The motor is water cooled WITH thermostat so on idle it only ever dribbles. When flushing it spits out tiny amounts then at regular intervals it shoots out a solid constant stream for about 10-25 seconds until the motor reaches its optimum operating temp again.

When running at full revs it will always have a constant stream because its constantly needing to be cooled. I have been told some Mercury and Tohatsu models are the exact same motors so it could be doing what its meant to do.

Huey will know for sure and he can help you.

Musty

[Guest Aussie007]

your idle could be set to low causing the engine to over heat sounding the alarm if your engine ran warm at idle and over heated while driving i would change the thermostat but over heating while idling and running fine i would be changing the impeller and possibly checking the idle RPM and the pee hole wouldnt cause the alarm to ring if it was blocked because u would still have water flow through the block it just wouldnt be peeing

[nsaykali]

your idle could be set to low causing the engine to over heat sounding the alarm if your engine ran warm at idle and over heated while driving i would change the thermostat but over heating while idling and running fine i would be changing the impeller and possibly checking the idle RPM and the pee hole wouldnt cause the alarm to ring if it was blocked because u would still have water flow through the block it just wouldnt be peeing

i had a feeling its got something to do with the low rpm.

i just did a quick search on the tohatsu website and found out that the TLDI direct injection model outboards have a user adjustable idle speed system,

"By pressing in on the key switch, you are able to adjust the idle from 700 to 900 RPM’s while you are using your outboard. Our TLDI® system will even remember the last setting and use this speed the next time you use your motor

i may have pressed this causing the outboard to idle low, i will hook up the flusher this afternoon and check these settings and report back with the idle reading and if that solved the problem.

thanks everyone

[a boat]

i had a feeling its got something to do with the low rpm.

i just did a quick search on the tohatsu website and found out that the TLDI direct injection model outboards have a user adjustable idle speed system,

"By pressing in on the key switch, you are able to adjust the idle from 700 to 900 RPM’s while you are using your outboard. Our TLDI® system will even remember the last setting and use this speed the next time you use your motor

i may have pressed this causing the outboard to idle low, i will hook up the flusher this afternoon and check these settings and report back with the idle reading and if that solved the problem.

thanks everyone

Hi, testing on the flusher is not the best way to determine the condition of a cooling system and the cost to service the water pump is not alot and can save a big expense from happening. Is the impeller the original impeller?

Cheers,

Huey.

[nsaykali]

Hi, testing on the flusher is not the best way to determine the condition of a cooling system and the cost to service the water pump is not alot and can save a big expense from happening. Is the impeller the original impeller?

Cheers,

Huey.

hi Huey, i purchased the motor with about 14 hours on it, it was a trade in, as the previous owner of the outboard wanted a 4 stroke as he was an elderly man.

so, im guessing it is the original impeller. the motor has not done much work since i have owned the outboard im guessing 40 hours. all of which has been in deep water, and never taken onto a beach.

after every outing, i flush the motor, and same thing happens, sometimes the water just dribbles, then when i put the rev lever up the water comes out properly and runs cool.

i always thought that if the impeller was broken, then NO water would run through the cooling system

[a boat]

hi Huey, i purchased the motor with about 14 hours on it, it was a trade in, as the previous owner of the outboard wanted a 4 stroke as he was an elderly man.

so, im guessing it is the original impeller. the motor has not done much work since i have owned the outboard im guessing 40 hours. all of which has been in deep water, and never taken onto a beach.

after every outing, i flush the motor, and same thing happens, sometimes the water just dribbles, then when i put the rev lever up the water comes out properly and runs cool.

i always thought that if the impeller was broken, then NO water would run through the cooling system

Hi, your engine so your call, but that impeller could easily be 10 years old and little hours of use is just as bad for an impeller as alot of use.

Yes if the water pump fails completely then of course no water will get to the powerhead to cool it and if that happens at high RPM you can have a dead powerhead, no matter what brand or technology so if that was my engine I would get someone that knows what they are doing to service the water pump and check the things that should be checked.

Cheers,

Huey.

[nsaykali]

Hi, your engine so your call, but that impeller could easily be 10 years old and little hours of use is just as bad for an impeller as alot of use.

Yes if the water pump fails completely then of course no water will get to the powerhead to cool it and if that happens at high RPM you can have a dead powerhead, no matter what brand or technology so if that was my engine I would get someone that knows what they are doing to service the water pump and check the things that should be checked.

Cheers,

Huey.

changing the impellor is not an issue for me, what confuses me is why its not pumping enough cold water into the engine, when the boat is in neutural, but as soon as i manually raise the revs a little the water comes out normally and does not heat up, and when its clicked into gear (no throttle) it does the same thing, but when a small amount of throttle is applied the water comes out normally and does not heat.

how many rpm should a outboard sit on idle?

like i said before it happend a while ago then it worked fine then its happening again, maby i have changed the idle setting which is a push in style(like the old chokes) where the key goes in?

i will check with the dealer i bought the boat from to see if the impellor was changed prior to having it fitted to my boat.

[a boat]

Hi, alot of questions there and if you got it from a dealer and you trust that dealer why not ask him that question instead of the internet. He SHOULD of replaced the impeller due to age and lack of use and if at low speed ON the water the tell tale is weak then the impeller is most likely worn and as you rev the engine up and the impeller turns faster it can pump more water.

Long story short, why not service the water pump and cooling system and if the problem still persists you know it is not due to the water pump.

Cheers,

Huey.

[spaners]

Hi, alot of questions there and if you got it from a dealer and you trust that dealer why not ask him that question instead of the internet. He SHOULD of replaced the impeller due to age and lack of use and if at low speed ON the water the tell tale is weak then the impeller is most likely worn and as you rev the engine up and the impeller turns faster it can pump more water.

Long story short, why not service the water pump and cooling system and if the problem still persists you know it is not due to the water pump.

Cheers,

Huey.

Mate,its only half a dozen bolts to drop the lower leg,then 4 more to remove the impella,just do it,then you have a good starting point.

Mine went last month,returned home at 10 am,droped leg 10.30,drove out,picked up new impella,fitted,back on water at 2.0pm...Just do it.

[dunc333]

i hope it is your water pump as a easy fix ,i have seen a problem with my friends toyatsu 115 alarm kept going off so changed waterpump changed thermo still kept happening ,what happened with his was where water tube comes up from the waterpump and joins the block there is a oring and that had perished and made intake in the tube from about 20mm down to 5mm dia thus restricting flow into power head of cool water and this is a time consuming fix ,just keep in mind after you change pump and thermo if problem still exsists cheers dunc333,

[chrisg]

Your variable idle range is 700rpm to 900rpm....even if it were at the low end the telltale would still be good.

To explain your point when the water pump is at idle speed the pump works as a displacement pump ie the water is pushed around the circuit. If there are any leaks such as the gap under worn impeller blades, the impeller having taken a 'set" due to lack of use or a torn blade the volume that is pumped is reduced and may show up just as you are seeing.

When you blip the throttle the pump speeds up and becomes a centifugal pump ie the water is flung around the system. the blades even move away from the wall it's all force work.

This is why pump problems tend to be far more noticable at idle speeds. My last change was from a visually fine impeller but two years old to a new one and my idle water pressure almost doubled.

Hope that helps.

C>

Edited December 15, 2010 by chrisg

[nsaykali]

Your variable idle range is 700rpm to 900rpm....even if it were at the low end the telltale would still be good.

To explain your point when the water pump is at idle speed the pump works as a displacement pump ie the water is pushed around the circuit. If there are any leaks such as the gap under worn impeller blades, the impeller having taken a 'set" due to lack of use or a torn blade the volume that is pumped is reduced and may show up just as you are seeing.

When you blip the throttle the pump speeds up and becomes a centifugal pump ie the water is flung around the system. the blades even move away from the wall it's all force work.

This is why pump problems tend to be far more noticable at idle speeds. My last change was from a visually fine impeller but two years old to a new one and my idle water pressure almost doubled.

Hope that helps.

C>

thanks for that explination.

i will look at getting the impellor changed before it causes me alot of damage.

hopefully a new impellor will sort the problem out

thanks for all the input really appreciate it.

[chrisg]

And don't be demoralised if it does'nt help. At least you now have a date of replacement for the future. Sometimes you just have to work through these things step by step.

C.