DF 70 Suzuki Oil Leak

[K-9 Guy]

I've got a 2000 DF 70, with 650hrs. The engine has been maintained religiously, nor has it ever given me any problems.

The oil leak is not really enough to lower the level on the dipstick between runs (4hrs) but it will leave a "slick" on the water. The oil is more apparent after trailoring it back home, in a full forward tilt position.

I've cleaned the mess all off & ran it all day @ idle with the "muffs" on all day @ my shop with no signs of leakage. I thought maybe it would only leak while tilted up, so I cleaned it all off again...let it sit all week & still no signs of leaking.

I put dye in it & checked the oil filter, Oil pressure switch, valve cover gasket, etc. Still no signs of leakage until I ran it in the water & trailored it home. I checked the crankcase vent hose from the valve cover to the air intake & it is DRY.

So far All I can really determine is that the oil seems to be the heaviest near the air box to throttle body connection.

Any Ideas????, Thanks in Advance...Elliot

 

[Silvertip]

Re: DF 70 Suzuki Oil Leak

While I don't have a solution, the problem is very likely to occur when the engine is run in the water because of the back pressure in the exhaust system. Running on muffs there is no exhaust back pressure. That said, since the leakage is in the vicinity of the air box, that would seem to indicate that the crankcase ventilation system is the culprit. Positive crankcase pressure can force oil vapors out of strange places. A couple drops of oil can also make a mess so you need to check every opening (including the oil cap) for leakage. Stick your finger into each of the air box ports to see if any of them are oily. If so, there might be some blowback on that cylinder, especially with the back pressure mentioned earlier. Check the plugs to see if one appears oily (or at least darker) than the others.

 

[K-9 Guy]

Re: DF 70 Suzuki Oil Leak

While I don't have a solution, the problem is very likely to occur when the engine is run in the water because of the back pressure in the exhaust system. Running on muffs there is no exhaust back pressure. That said, since the leakage is in the vicinity of the air box, that would seem to indicate that the crankcase ventilation system is the culprit. Positive crankcase pressure can force oil vapors out of strange places. A couple drops of oil can also make a mess so you need to check every opening (including the oil cap) for leakage. Stick your finger into each of the air box ports to see if any of them are oily. If so, there might be some blowback on that cylinder, especially with the back pressure mentioned earlier. Check the plugs to see if one appears oily (or at least darker) than the others.

Thank you for your prompt response !! I called the dealer & they said that there isn't a PCV valve as in other 4 stroke engines....SOOOO...My question is ??? How does it reduce crankcase Pressure ???

 

[Silvertip]

Re: DF 70 Suzuki Oil Leak

The crankcase vent hose that you mentioned in your first post. But you said it was dry so that apparently is not the problem unless it is pinched or plugged.

 

[K-9 Guy]

Re: DF 70 Suzuki Oil Leak

The crankcase vent hose that you mentioned in your first post. But you said it was dry so that apparently is not the problem unless it is pinched or plugged.

Thank you, now for the next question... On any other 4 stroke engine, there would be a PCV valve connected to the vacuum source & a "fresh" air tube which would bring in ambient air thereby creating a circulatory system & eliminating any way of a vacuum being created on the crankcase.

The tube I described earlier, I would consider to be the "fresh" air tube...but where does the vacuum side come from ???

Sorry if I seem dense for some reason

 

[rodbolt]

Re: DF 70 Suzuki Oil Leak

first have a cyl leakdown test run to see if there is excessive blowby past the rings. if there is try a good decarb and retest.
so far most 4 stroke outboards do not use a PCV system,nor quite a few sterndrives, but rather a simple breather pipe from the crankcase or cam cover to the airbox.
wont see much blowby on the muffs due to low combustion pressures and low RPM's.
this is a problem we fight a lot, especially the guys with trailers that tilt the engine up.
the F200/225 Yamahas are a good example. they can be modified but not by yamaha.
what usually happens is at higher speeds the blowby vapors overwhelm the airbox's ability to vent the gasses back into the intake air stream.
the vapor then condenses back into a liquid and settles in the airbox thand throttle shutters. then when tilted it all collects at the bottom and tends to seep out of the air box at the seam.
last F225 I fixed I kinda cheated, I simply sealed the seams of the airbox with an ABS type glue and the problem went away.
I dont design them I just get to listen to the customer complain when oil is dripping into the splashwell.

 

[K-9 Guy]

Re: DF 70 Suzuki Oil Leak

first have a cyl leakdown test run to see if there is excessive blowby past the rings. if there is try a good decarb and retest.

Thank You Very Much For Your Response, So Since I'm full of questions...Here's One.

Of Course I Will Do As you Suggested With The Leak down Test, but assuming that it does need decarboning but since I just did one about 150 hrs ago, am I suffering from some malfunction or should this be a regular maintenance item ?

I don't idle much & usually run it wide open for about 1/2 hr before going to my next fishing hole, where it will sit for @ least 2 hrs. For what it's worth I use regular fuel & Synthetic 10W-40 Engine Oil With changes every 100 hrs.