Reply With QuoteDo u have a rubber grommet in the small hole either on the top or one missing from the bottom of the hole (located on the white impeller housing)
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Hi All,
While out on the water a few weeks back we ran into an issue where the impeller had stopped drawing water up to cool the motor down.
The alarm on the dash started and after a on water inspection of the issue along with an attempt to wait for it to cool down to try and crawl back we had to resort to getting a tow back to the boat ramp.
Fast forward to this weekend, I have pulled apart the motor to get to the impeller to confirm there was no debris or anything stopping the unit from working.
I did have the boat serviced a couple of months back and the mechanic did replace the impeller but I am wondering if the new impeller as shown in the photos is the correct size? It looks too big to me but I have yet to be able to google anything that has answered the question for me.
The other thing I did notice was that water was not coming out of the port at the top of the motor where it normally did. And I am pretty sure that water came out the top when the motor was off and the earmuffs were on the motor to flush it out.
I tried clearing the hole with a length of wire and blowing it out with compressed air without any luck.
So I am hoping the brains trust here may know something I can try?
Notes:
* Motor turns on but water is not being pushed out the top
* Overheats after being on 30sec to 1 min
* No visible debris or blockage around the water pump
* Impeller looks too big?
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Do u have a rubber grommet in the small hole either on the top or one missing from the bottom of the hole (located on the white impeller housing)
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This is whst im talking aboutAttachment 120707
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There's a dozen things going on here, first off, it might be time for a complete water pump kit, not just an impeller (impeller looks OK) water coming out the tell tale does not mean the engine is cooling, is the tell tale outlet simply blocked? is the engine actually over heating? it might be a false alarm, or an oil problem? you need to find the simple answers first.
since u ran the engine on the muffs and it didnt pump water you likely cooked the bottom of the water pump housing, when u run a engine and the water doesn't siphon up to the impeller the impeller spins dry and really heats up to the point it melts the lower impeller housing around the shaft just above the shaft seal
take the metal plate off as pictured in the circle than take a look at the plastic and see if it looks melted, different colour usually when the shaft spins without water it boils the plastic housing also look to see if the hole is round or if its oblong an indication its screwed
if its melted your water will come in the intake up thru the housing compress than push strait back thru in to the intake side of the housing
Pretty dumb question maybe as i can't clearly see the photo but was the key in place on the shaft. As Noelm says, start eliminating all the small things first.
Impeller is not too big - that's how they are. You need to attempt to try and ascertain whether you have a water flow issue from the leg, a sensor issue or an internal blockage somewhere in the engine. Yamaha motors are reasonably well known for water gallery blockages due to salt deposit build up. Initially, I would attempt to run the engine with the leg removed and the garden hose fed into the water tube. I would also be removing the thermostat to see if there are any obvious deposits or blockages and to see if there is any water flow getting to there as well as the tell tale hose and any fittings if possible where they leave the engine and check them too. If you can run the motor without the leg without issue, it's the water pump (or as has been mentioned the possibility of a water tube grommet missing) and I would simply order a full pump kit (not just an impeller) and fit it. If the fault persists with the leg removed, removal of the water jacket / head is probably next in line unless there is an obvious blockage found anywhere.
If the alarm goes off in only 30 seconds, you might start to think about oil system, not just overheat.
I went down this track about 6 months ago with a 2st 30 yam.
Every time i got home i flushed for 5 minutes using muffs.
Ended up there is a 3.8mm port hole under the exhaust jacket that leads to the cylinder water jacket.
This port was blocked with salt in my motor.
The motor soon overheats and drops to limp mode when the top 1/4 of the exhaust water jacket overheats.
The motor pumps water everywhere else but there.
In my opinion the port is undersized and not in a very good spot to be truthful.
Every 4th flush I use salt-X in a drum to ensure that one port doesn't block again.
Jack.
Cheers, will check that out as wellOriginally Posted by gazza2006au
Good notes, we did have to replace the oil sensor at the last service as the old one had died.
Cheers all for the suggestions, i'll have a look at the water pump lower unit again.
I did notice that the top part of the housing looked like it was old so there is a chance it is an issue with it. Unsure of the state of the o-rings or other rubber grommets inside at this stage.
Also to better explain what I mean about the water coming out with the motor off, this video at the timestamp shows the water coming out the top even prior to the motor being started:
Just another couple of notes to add as I was in a rush out the door this morning when I posted originally.
* The engine did start to smoke when it overheated
* The impeller was working prior to our last stop, we noticed that the water was running when we were trolling and subsequently it wasn't when the overheating issue started
* At the time it happened we were running the motor flat out
* I believe the oil sensor had a different tone to the one we had when it overheated
* The motor started fine, there was no rough idling etc
If the motor is still together and running try a very heave dose of salt-x in a drum and have it run for about an hour.
Yours sounds 100% like mine was doing, I ended up having to do a full powerhead rebuild.
In the attached image is a small red dot I placed where the water jacket port was blocked.
The temp sensor is very close to this spot and will drop you into limp mode quickly.
Mine went beyond limp mode to trashing the pistons.
Attachment 120721
Jack.
I wouldnt worry about the top cover looking shaggy so long as there are no cracks its reusable the internal ring/plate is what wears out
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with the leg off, try and jam a garden hose over the water pickup tube, turn the tap and check the water flows through the block ok to eliminate the engine!
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