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Cooling issues with 18hp Fastwin

N

Nobrot

Contributing Member
Getting really annoyed at this motor (15032 ) Having spent a few months on and off getting her running well enough to do a complete refurb I'm still stuck on the cooling....have replaced the actual impellor and made sure all pipes are clear by using both water and compressed air, I've run the lower unit in water using a drill and it has a decent head of water, poured water down from the thermostat housing and water runs out of the exhaust port. Stripped the power head and blown out all water channels ( that I can see..) New gaskets all round. Water feed pipe secure in rubber housings both top and bottom. When she starts there is an initial flow of water from the exhaust port but only for a few seconds and nothing after that even running her for a minute or so, some steam (?) is visible from the exhaust port after that minute but I shut her as soon as. No visible leaks from anywhere and I'm running her at the moment without a thermostat.
I've noticed that there are 3 screw holes in the ali pump casing and wear plate but 4 in the actual lower unit and having checked on the tech diagram it looks like that is Ok but I'm not 100% sure as the diagram in a bit unclear. The wear plate is a little worn, though cleaned and straight, but I wouldn't have thought enough to cause a problem. The impellor pin in Ok.....anyone got any ideas as I dont want to get this far just to scrap her. Thanks.
 
I am guessing you are running in a bucket or tub? Keep the water above the cavitation plate. I had an issue with my 9.9 not producing water out the exhaust relief, then saw I had a super low water level. Water should be way above the pump area.
 
Hi, Yeah water is well above the cavitation plate, exhaust outlet is about 3-4 inches above the water level.

As a side note, I think this engine has had this trouble long before I got hold of her. The lower piston in particular shows signs of over heating on the paintwork but I've had the head off and there appears to be no damage, rings look fine, no scoring and all channels clear...new gasket fitted. I think I've pretty much covered everything...however, clearly NOT everything.
 
water pump needs to be under water before starting the motor. Those pumps don't self-prime very well. 3 screws are correct. Did you clean gearcase surface and apply sealer under the pump plate? An air leak there can affect pumping. Those pumps are normally very trouble free
 
Have to ask.----Was the copper tube installed into the exhaust housing grommet BEFORE you installed the lower unit ?
 
fdrgator said:
water pump needs to be under water before starting the motor. Those pumps don't self-prime very well. 3 screws are correct. Did you clean gearcase surface and apply sealer under the pump plate? An air leak there can affect pumping. Those pumps are normally very trouble free
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No I didn't.....I'm sure it's something in that area as everything else seems to work, I'll do it. Thanks.
 
racerone said:
Have to ask.----Was the copper tube installed into the exhaust housing grommet BEFORE you installed the lower unit ?
Click to expand...
Yes, all double checked. I've gone through everything I can think about and what I've been told 2 or 3X and still it's the same problem. Thanks.
 
racerone said:
Normally these are easily solved.----Must be a blockage ( old impeller bits ? ) somewhere.
Click to expand...

Tell me...I cant see or find anything and I've almost stripped her down to bits. Water flows where it should..or seems to, have had compressed air, strimmer ( weed whacker ) cord, poured water into the therm housing and it flows out freely and out of the exhaust port. It's only when shes bolted back up there's a problem. It's something pretty simple I'm sure and it looks like it's been the same problem for the previous owner...........
 
I have finally sorted the problem and in doing so found another annoying one. Several, at least 2, of the rubber blades are facing the opposite way.....I have lightly greased them before installing clockwise into the housing, screwed the housing down well etc etc only to find after a minute of so she stops pumping, strip down and the same problem....I tried a new impeller and the same thing is happening......The pump housing looks Ok, there doesn't appear to anything untoward that I can see, is there a right or wrong way to install these particular impellers, I've never had this problem with any Evinrude/Johnsons before. I'm going to put the original one back in but if I remember correctly I had the same problem with that..Any ideas ??
 
Perfectly normal with those long-bladed impellers. When the motor stops, it will often bounce backwards off the last compression stroke, flipping an impeller blade or two. As soon as it is restarted, they will all re-flip correctly.
 
fdrgator said:
Perfectly normal with those long-bladed impellers. When the motor stops, it will often bounce backwards off the last compression stroke, flipping an impeller blade or two. As soon as it is restarted, they will all re-flip correctly.
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Completely understandable but she stops pumping water whilst she's still running even though she does pump water from the start everytime if only for a few seconds. The longest she was pumping before stopping pumping was about a minute....then nothing.
 
Where are you testing ?----I suggest putting the motor on a boat.----Launch the boat and test run.-------Have you checked the inside exhaust cover for a hole.------That would allow exhaust into the cooling system ?
 
Have you checked the bleed hole in the pump housing? Is the pump housing worn? It sure sounds like air or exhaust is getting into the intake side of the pump.
 

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  • Water pump housing bleed hole.jpg
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fdrgator said:
Have you checked the bleed hole in the pump housing? Is the pump housing worn? It sure sounds like air or exhaust is getting into the intake side of the pump.
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Correct me if I'm wrong but the bleed hole, as the name implies, should allow air or water through..??
 
It allows air to escape.-----If there is no air then a wee bit of water escapes.------This concept has existed for many years.
 
racerone said:
Post information-----Is this hole blocked now ?----I believe the hole was drilled there for a reason !
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From a brief look it does look like it could do with unblocking/clearing, looks like the rubber grommet that holds the water pipe in place has perished somewhat and may be causing the hole to be blocked......which has just given me another thought.
 
racerone said:
??---What thought ??-------Have you checked the grommet halfway up the exhaust housing ?
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Yeah, that grommit seems fine but will double check, thanks. The other ' thought ' was if the pump outlet grommit is perished then it could cause a potential blockage of perished rubber which I haven't checked or block the breather pipe. I'm going to go over the whole pump unit up to the top of the water pipe with a fine toothed comb. The problem is somewhere there.....Cheers.
 
Nobrot said:
Yeah, that grommit seems fine but will double check, thanks. The other ' thought ' was if the pump outlet grommit is perished then it could cause a potential blockage of perished rubber which I haven't checked or block the breather pipe. I'm going to go over the whole pump unit up to the top of the water pipe with a fine toothed comb. The problem is somewhere there.....Cheers.
Click to expand...


Progress report...nothing much changed I'm afraid. Stripped down the pump unit again, checked, cleaned and sealed with gasket sealer the joints just to eliminate are air ingress into the pump unit. Pumps loads of water from start for about a minute or so then just stops, doesn't slow down any, just stops. I left it running mainly out of pure spite and after 30 seconds she started pumping water again for a few seconds...loads of steam as you would think then stopped again. I turned her off as she was getting hot, 100c hot. So it seems that as she gets warm she stops pumping water. I'm running her without a thermostat !!!
 
These pumps are ultra simple and reliable.----I suspect an issue in exhaust housing or exhaust cover on the bock.-----Be an easy repair here.
 
Just to clarify---That bleed hole is there to keep the well around the drive shaft filled with water, which provides a water seal to keep the pump from pulling air down through the hole that the drive shaft goes through.

When the motor is first started, the pump is under water (hopefully) and it works ok. But when running, the exhaust blows the water out and the pump is now surrounded by air (exhaust) which could be drawn into the pump if it were not for the bleed hole.
 
fdrgator said:
Just to clarify---That bleed hole is there to keep the well around the drive shaft filled with water, which provides a water seal to keep the pump from pulling air down through the hole that the drive shaft goes through.

When the motor is first started, the pump is under water (hopefully) and it works ok. But when running, the exhaust blows the water out and the pump is now surrounded by air (exhaust) which could be drawn into the pump if it were not for the bleed hole.
Click to expand...

I checked the bleed hole but it is blocked by both the rubber grommit and the copper water pipe....unless the grommit is wrong. Should take it out and cut it down untill the hole is visible
 
racerone said:
These pumps are ultra simple and reliable.----I suspect an issue in exhaust housing or exhaust cover on the bock.-----Be an easy repair here.
Click to expand...

I did think that a while ago but due to the amount of what appears to be very seized bolts I gave it a miss. I'll have a go. Thanks.
 
Nobrot said:
I checked the bleed hole but it is blocked by both the rubber grommit and the copper water pipe....unless the grommit is wrong. Should take it out and cut it down untill the hole is visible
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The hole is drilled at an angle from the OUTSIDE all across the grommet cavity, and on into the well. The outer end of the hole is blocked by the grommet but the inner end of the hole should be open so water can flow into the well.
 
fdrgator said:
The hole is drilled at an angle from the OUTSIDE all across the grommet cavity, and on into the well. The outer end of the hole is blocked by the grommet but the inner end of the hole should be open so water can flow into the well.
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Ah...Ok I think I see where you're coming from now, so fishing line and compressed air should do the trick on the pump but I will also strip down the exhaust cover etc etc.
 
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