df175 loss of oil?

[Harper]

One other thought....

a crankcase has to breathe. I can't find much of anything in the manual about crankcase breathing. Does it exhaust to the intake somehow (likely), or to the atmosphere (less likely, I would think)? Could be that a blocked breather tube could build pressure in the sump, especially during high RPMs, and cause more blow-by past the rings. Could also be possible that oil vapors and droplets could be sucked into the intake and burned. (Art, does the throttle body show any signs of oil?) Anybody know how the crankcase breathes?

[artdf175]

Mike
not seeing any oil on the outside of the motor.. anyplace..
there is a tube that exits starboard side mid motor and exits cowling bottom
I am thinking that may be a breather ..will look in my shop manual and see if I can find a picture
thanks for all the above explantion. that makes sense and probably makes the case for the rings letting oil get by...
art...............

[artdf175]

q) When you done the compression test was the engine hot or cold, and did you make sure the throttle plate was wide open when you done it.
a) the mechanic did this.. and can only tell you it was cold he did the tests the following morning when it was cold
I can only assume that he knows how to do this..
going to buy a few new tools for my tool bin.. .. and will be checking oil pressure

q) Usually valve stems are lubricated by being bathed in the oil that flows along the top of the cylinder head
I found the schematic on the oil flow in the manual.. yes you are correct..
after I get the boat back, I will tell you what the mechanic finds... and then will look at the cylinder heads myself.

but not understanding why it only uses oil at higher rpms. yes the pressure is up.. but I can only think that if it was getting around the rings it would happen at any rpm
higher oil pressure should just push the oil back into the sump not push it by the rings
the valve stems?? at lower rpms there just might be not valve action .. higher rpms more cycling of valves, more often the vacuum of the down stoke that in turn sucks the gas into the chamber where is burning up ..the mechanic is hearing pressure leaking past the exhaust valves, not the intake valves.. just shows that indeed it is fouling plugs and valves.
--maybe if there are any Suzuki mechanics reading the thread-- if they could chime in on fact why with higher rpm's oil is getting into combustion chamber and not at idle.. ???

q) a crankcase has to breathe. I can't find much of anything in the manual about crankcase breathing
a) I could not find anything in the book on the crankcase breather either. but most 4 cycle engines, the breather is run back through the engine to burn off excess gases
will certainly be looking at that area.. if oil is getting here, breather tube should be dripping oil ..
there is one more repair or shop manual out there it seems.. will be looking into getting one of those that might provide a bit more detail in some of these areas..
the breather that I had seen on the right side of the motor.. may very well be a fuel vent hose .. but again can not find anything in the manual and will look at it again when I get the boat back..

[redlowrey]

q) When you done the compression test was the engine hot or cold, and did you make sure the throttle plate was wide open when you done it.
a) the mechanic did this.. and can only tell you it was cold he did the tests the following morning when it was cold
I can only assume that he knows how to do this..
going to buy a few new tools for my tool bin.. .. and will be checking oil pressure

q) Usually valve stems are lubricated by being bathed in the oil that flows along the top of the cylinder head
I found the schematic on the oil flow in the manual.. yes you are correct..
after I get the boat back, I will tell you what the mechanic finds... and then will look at the cylinder heads myself.

but not understanding why it only uses oil at higher rpms. yes the pressure is up.. but I can only think that if it was getting around the rings it would happen at any rpm
higher oil pressure should just push the oil back into the sump not push it by the rings
the valve stems?? at lower rpms there just might be not valve action .. higher rpms more cycling of valves, more often the vacuum of the down stoke that in turn sucks the gas into the chamber where is burning up ..the mechanic is hearing pressure leaking past the exhaust valves, not the intake valves.. just shows that indeed it is fouling plugs and valves.
--maybe if there are any Suzuki mechanics reading the thread-- if they could chime in on fact why with higher rpm's oil is getting into combustion chamber and not at idle.. ???

q) a crankcase has to breathe. I can't find much of anything in the manual about crankcase breathing
a) I could not find anything in the book on the crankcase breather either. but most 4 cycle engines, the breather is run back through the engine to burn off excess gases
will certainly be looking at that area.. if oil is getting here, breather tube should be dripping oil ..
there is one more repair or shop manual out there it seems.. will be looking into getting one of those that might provide a bit more detail in some of these areas..
the breather that I had seen on the right side of the motor.. may very well be a fuel vent hose .. but again can not find anything in the manual and will look at it again when I get the boat back..

You haven't done the things I asked you to do, I am a mechanic this is what I do for a living.

[Harper]

if they could chime in on fact why with higher rpm's oil is getting into combustion chamber and not at idle.. ???

I'm not a mechanic by profession, Art, but here's the thing about why your oil consumption is high at higher RPMs and not at idle (and why redlowrey and I are telling you it's rings instead of valves).

Remember red's statement, "When valve guides or seals wear the oil will be sucked down past the valve stem in to the combustion chamber and it will mix with the fuel air mixture and burn."?

The reason that this indicates ring leakage is that with a closed throttle plate, such as it would be at idle, your manifold vacuum is high and also the combustion chamber pressures are very low, or even negative (on fuel injection automotive engines the injectors are actually shut off at closed throttle until the RPM decreases to around 1500). And of course, these pressures are both much higher as you throttle up, overcoming the tendency for the oil to be sucked past the valve seals/guides. It's the negative or near zero combustion chamber pressures at idle that will DRAW the oil along a leaky valve stem.

You also have a tendency for rings to flutter at high RPM if they are worn or were not seated properly during the break-in period.

Consider: 1) You don't know for sure how the engine was treated those first 25 hours of operation. 2) It has burned oil "from the beginning." (This actually should say, "from the time that you obtained it with 25 hours on the clock.")

Now ask: Is it likely that an engine with only 25 hours would be sucking oil past valves seals and guides, with little or no wear on these components at that point? Or is it more likely that rings never seated properly due to abuse during the most critical half of the break-in period?

One final indication: when the valves leak, due to the conditions I pointed out above, the plugs are usually somewhat "wet" with oil, because the oil did not burn off. When they are merely black with soot, it is because the oil got there during a period when it was burned along with the fuel/air mixture during open throttle operation (or because of very rich air/fuel mixture, but that's not our problem here).

[artdf175]

You haven't done the things I asked you to do, I am a mechanic this is what I do for a living.

I will check and do the things you suggested, as soon as I get my boat/motor back from the suzuki dealer/ mechanic..
I will also have more information and because of your input, can ask some pointed questions of him directly..
Thank you..
Art..

[artdf175]

Mike thanks for the explanation --I understand what you are saying
will keep you posted to what I find out from the mechanic and then what I discover after I get it back..
thanks to you and Redlowery I am understanding the problem much better.

and you are correct.. I don't know what the guy did the first 25 hours..
for all I know he could have run it with low or almost no oil and damaged it
I don't think he was the most sophisicated boat owner around.

Art..

[artdf175]

You haven't done the things I asked you to do, I am a mechanic this is what I do for a living.

here are some updates to your questions that I ask the mechanic

Q) When you did the compression test did you make sure the throttle plate was wide open?
A) YES

Q) If you pull the plugs out and get each cyl to tdc and get a torch with a thin probe I will bet the pistons are wet indicating the oil is coming past the rings.
A) Would have to be extreme oil leakage for the piston crowns to actually be wet.

Q) When valve guides or seals wear the oil will be sucked down past the valve stem in to the combustion chamber and it will mix with the fuel air mixture and burn.
A) Yes, I agree

Q) Check the oil pressure,
A) low oil pressure would indicate other problems, not related to burning oil
and
Q) check the bucket clearance on the valves (not sure what bucket clearance is??)
A) Bucket clearance refers to valve / camshaft clearance. Would have to be extremely out of tolerance to affect compression, has no bearing on oil loss.

Q) ask question on crank case breather hose
A) Your thoughts on breather hose are correct. Did check it to make sure it was open.


Can I call you RED??
other than increasing the viscosity of the oil? what did I miss
mechanic is running an internal engine cleaner through motor today
is then going to re-test compression
will report back findings
Art..

[artdf175]

question on repair manuals
I picked up a Suzuki 1996-2007 Outboard repair manual by SELOC
is there a better book available ?
thanks

[Harper]

I use the Suzuki Manual, Suzuki Outboard 99500-96J03-01E DF150 / DF175 Service Manual - Browns Point Marine Service, LLC
I'm not familiar with SELOC

[redlowrey]

The reason I wanted you to check the oil pressure is because high oil pressure will create more splash from the crank journals and the rings cant wipe the excess oil off the walls of the cyls. 2 When oil gets past the rings if it does not get burnt in the combustion chamber it sits in top of the piston just in from the ring lands, and gets blown out past the exhaust valve, wipe inside the prop and surrounding area with your finger I bet it is black and oily. 3 You said in your earlier post compression was down and you could hear exhaust valves leaking, well what do you think would happen if there was no clearance between the cam lobe and the valve, valve clearance is critical. A blocked breather would make it use oil but also it would push oil out of your front and rear seal. Pull the cam cover off and check the bucket clearance, if your mechanic has not heard the term bucket clearance I think he must work on old O.V.H engines.

[artdf175]

I know what you are saying..
I will check the oil pressure when I get the boat back.. probably this weekend
the manual only refers to checking for low pressure. I agree with you.. if the pressure regulator on the oil pump is failing and letting pressure go above tollerance (if I remember correctly about 90 psi max) would create a number of problems.. this being one of them..

as you can see from the photo I submitted earlier, when I pulled the plugs prior to taking it in, everything was clean.. it was only after the motor was run at higher rpm and not idled for some period that the plugs came out black
again.. I did wipe down the inside of the prop.. there was absolutly nothing there..another reason for the confusion on where was the oil going.. it was clean as a whistle..
Compression.. he did this after it was run, where the plugs came out black.
he ran the cleaner through the motor late yesterday .. is checking compression again, this morning some time.. waiting to see what the results are..
I understand your point on the valve clearance.. if compression fails test that will certainly be the next item to verify.. however question/comment: would that not make the engine run bad? or how would the engine run if there was no valve clearance? it has always been an easy starting and smooth running and very responsive to throttle comands ..
he checked the breather and there was no blockage
and the comment re what is bucket clearance? was my comment not his.. he was aware of what that term is..

and.. a big thank you for you concern and input.. very much appreciated
Art............

[artdf175]

I use the Suzuki Manual, Suzuki Outboard 99500-96J03-01E DF150 / DF175 Service Manual - Browns Point Marine Service, LLC
I'm not familiar with SELOC

Seloc Marine - Product Finder Results
Mike this is the home page I found this book at a local marine supply store
printed manaul #1602 covers all Suzuki outboards from 1996-2007
I will check out the manaul you referenced.
Thanks

[artdf175]

here is the compression test results

Before treatment
1 -- 140 psi
2 -- 130 psi
3 -- 120 psi
4 -- 160 psi

After treatment
1 -- 145 psi
2 -- 145 psi
3 -- 125 psi
4 -- 160 psi

Looks to me like you are in line for a tear down. It's my "guess" that number 3 has a burnt exhaust valve.
=============
so my plan is before tearing it down:
1) test oil pressure to see if too high..
2) check valve clearance.. see if they are in tolerance
--
run it for a bit more then do another compression test after doing above
what would cause a valve to get burnt?
I see I have a litte more homework to do..

[Harper]

Hi Art,
Valve gets burned because of lack of bucket clearance. The valve head is cooled by conduction of heat to the head each time the valve closes. If it doesn't close completely or for a long enough period during the stroke, it cannot cool properly, and is thus burned.