Suzuki DF4/DF6 cooling puzzle

[Anonymous]

I have a four year old Suzuki DF6 which was serviced twice by 'professionals' and the impeller was never changed (never billed). This year I did the lube etc. myself and was (shame) not aware that the impeller even needed to be changed. In the summer the tender is our 'car' and is in daily use at anchor. A week ago the tell-tale became erratic then finally stopped.

I felt along the rear underside with the engine running and found warm moist exhaust gas coming out. The entire engine was hand-hot; I could leave my hand on with minor discomfort, there was no evidence of steam, overheating sounds or rough-running even on full load. Anyway, I obtained a spare impeller kit with face plate and gasket (I did need the gasket though the face plate would have cleaned up fine). It was a fiddle especially working on it in the tender but it was do-able and I did a decent job. Started the engine and still no tell-tale! Maybe (or maybe my imagination) a slight spray, like a plant spray out of the tell-tale along with the exhaust, but no solid water.

The local dealer is at a loss without seeing it (though without taking it to pieces I can't see how 'seeing it' would help and he can't look at it for several weeks anyway).

Possibly some water passage is blocked - I have pushed 18" of thick enamelled copper wire right into the tell-tale and that made no difference.

One odd thing. On the water pump housing there is a hole that is blocked. It is only about 3mm and I couldn't even be sure that it was a through hole. It tried to clear it out with a screwdriver as I didn't want to drill into allow and cause terrible trouble if it was supposed to be blind. On reflection, I did notice that there was a hole in the gasket and impeller face plate that lined up with the hole so probably it is a through hole that is blocked? To go back in again is quite a lot of work in uncomfortable conditions and anyway I would need to be 100% sure before running a drill down that hole as it seems to go into the oil chamber - maybe it turns 90 degrees hence the danger in just drilling it out without knowing what is going on. From what I saw, I couldn't see what the hole could have been for.

Another possibility is that the thermostat (that's a new item on this generation of engine) is wide open causing all the cooling water to bypass the tell-tale.

The crux is this....I really need this engine until we finish cruising in late September. If I am happy that it is being cooled properly and not coming to any harm then I would take the gamble that the new impeller is not going to fail without my knowing. Though who watches the tell-tale all the time? The first you'd know about overheating is the engine sound, steam or smell, surely? It's never happened to me on an outboard so I have no frame of reference. To put it another way, why not carry on using it until the winter break then sort it out under better conditions with a workshop manual, or at least with time and the ability to buy spares easily?

As we are cruising, I don't always get Internet connection though I can get my emails, which include answers to forum posts so many thanks in advance if I don't get the chance to thank you directly.

 

[Shearwater]

Had similar prob with Honda 8hp. During major service, the mechanic showed me all (as in ALL) waterways blocked with salt - very fine crystilline structure and very hard but of course soluble in warm fresh water. Was advised to flush whenever possible; intend to use a large bucket topped up with the marina's hose line. Hope this helps,

 

[Anonymous]

Yes, that makes sense. The stuff in the little hole was as you described. I have seen people use a device like ear muffs to run from fresh water. Are these a universal product for all engines or made for each engine?

 

[graham]

It cant be due to the thermostat being wide open as you normally get a telltale flow with a hot or cold engine The water flows past the telltale on the way to the thermostat housing.

. I completely stripped a DF4 down a few years back to clean the cooling channels and loosen a seized gear change..Ill have a look see if I still have some photos I took.

Found them.

This pic shows the cooling channel in the top of the drive leg the pipe coming up the center delivers the water up from the pump .I think the telltale hole is in the top right of the pic.

This pic shows the bottom of the engine which mates up with the sump pan which is the base of the engine cover.The whole lot bolts down to the drive leg with two (expensive) gaskets.


Its not a difficult job but a bit fiddly .

If it was mine I would get it home and run it in freshwater while having another go at probing the telltale hole before commiting to stripping it down.Its fairly straight forward to strip ,all of the bolts need a 10mm socket.

You have to remove the carb to get at the thermostat so get an inlet manifold gasket as well for reassembly.

Good luck

 

[steve28]

we have had remarkable results using rydlyme descaler, when the tell tale is eratic or not working. position the engine so that the block can be filled through the tell tale hole, leave overnight then run the engine in a tank of fresh water.

 

[Anonymous]

With no tell-tale, I get exhaust gas from the hole which the local dealer's mechanic said was normal (he thought that it was the impeller at this stage, as I did). Is the tell-tale at a water/exhaust elbow? My exhaust is cool and seems normal in volume and sound.

 

[Anonymous]

If you see my post directly above, you will see that with the DF4/6 the exhaust is mixed with the tell-tale so while using a descaler sounds like a brilliant idea in some cases, I fear that with these engines it will get into the cylinder via the exhaust valve.

 

[Shearwater]

Not poss with my Honda - someone will tell you. Good luck.

 

[graham]

I have added the pics to the above post. If you have exhaust smoke coming out the tell tale hole I wonder if the gasket is gone allowing the cooling water to go straight into the exhaust and back down the leg?

PS I am not a mechanic .

 

[Anonymous]

Brilliant pics, that's a great help, thanks. Yes, exhaust gas comes out the tell-tale with a water spray. The amount of water is minute, like an perfume atomiser. No steam at all. The gas is warm, not hot. When I put my finger over the hole I block the flow of exhaust and more comes out by the exhaust near the prop, underwater; you see considerably more bubbles. The dealer's mechanic did not seem surprised and confirmed that a new impeller seemed the most likely solution but looking at your pic, it doesn't make a lot of sense.

Assume that the gasket is blown (I still can't sort out in my mind which gasket that would be and what exactly is happening) then if I continue to run the engine, given that it does not seem to be overheating now, does it seem reasonable to continue for a while - say another 50 hours running at the worst case? It has probably been in a state for quite some time but maybe getting worse?

 

[Anonymous]

Sorry, I should have said that "getting it home" isn't an option as we live on the boat and we don't have a car. It cost €50 by taxi to get to the dealer to buy the spare impeller, the dealer can't look at it yet and we would be stuck in Cannes (unaffordable for long and we must move on anyway) so I am limited to what I can do in the tender itself or on (a teak) deck. I don't even have a good vertical support that allows me to work on the propeller side of the engine due to the way I am set up. I am a long way from 'ideal' when it comes to working on the engine until we stop for the winter.

I can immerse the prop drive unit in fresh water, in a bucket, inside the tender and that might help unblock that little hole. I will try that in the am.

Many thanks for all your kind help.

 

[VicS]

Are you absolutely sure the tell tale is not blocked at the engine end? Can you blow up it?

I'd only expect to see a single way in and a way out of the water pump.
Are you sure you got the water tube correctly positioned in the pump discharge.

If you can keep your hand on the cylinder head for more than a few seconds it is certainly not overheating and depending upon how thick skinned you are it could well be over-cooling due to a faulty thermostat. I don't know about the Suzuki but it is often the thermostat that is part of the pressurised cooling system control.

If it is overheating you wont keep your hand on the cylinder head and it will sizzle if you spit on it. Also you will likely get a load of steam from the exhaust relief hole on the leg

If the pump is pumping water to the engine Ok it is usually possible to see a few spots of water or a fine spray coming out from the exhaust relief hole.

Provided you keep it upright you should not get anything entering the engine via the exhaust port. There is usually an inner exhaust pipe anyway.

A good place for outboard questions is the iBoats forums at http://forums.iboats.com/

 

[graham]

Ill try to explain it a bit more clearly.

There is a gasket between the top of the drive leg and the bottom of the plate that forms the motor housing then a second gasket between the plate and the bottom of the engine.

The whole thing is bolted together with two gaskets between the mating surfaces.


It sounds as if the bottom gasket may be gone allowing cooling water from the channel you can see in the pic to leak across and into the exhaust which goes back down the centre of the drive leg.

This would also explain the exhaust gasses coming out the telltale hole. You will need new gaskets anyway if you strip the motor off the drive leg to clean the waterways.

Not impossible to do onboard if you could rig up a stand to clamp the motor to but inevitably a bit of oil will get spilled.

This pic shows the base plate of the engine housing which is sandwiched between the drive leg and the motor with one gasket on top and another below.

PS as VIc S says if the motor is overheating you wont be able to keep your hand on it .

 

[Anonymous]

Thanks for your time and trouble, I have saved the thread and pics in my 'manuals' file. It seems likely that the gasket must have gone somehow. A rogue mechanic did service it the year before last though what he was doing taking it apart to that extent is beyond me...though he takes car engines apart for fun. Anyone who knows Almerimar will know who I mean.

So, given that it is running like a sewing machine with no overheating (thanks for your comments, Vic) and given the difficulty in trying to do anything without transport and facilities (it would almost be cheaper to buy a brand new engine than stay in Cannes marina and taxi to and from the dealer for parts), I will just keep an eye on it and not get myself into the situation where we could not safely and easily row back if the engine failed.

From your pics and description, I can't see how this can cause damage to the engine other than, possibly, under-temperature operation and that is more of an economy issue, I think.

 

[jastic]

I have exactly the same problem, did you find a solution?
many thanks