oil leaking from DT 40

[botchley]

I have an '87 DT 40 two stroke that has started to leak oil from the exhaust, some from the upper exhaust port but mostly out through the prop. It does this when just sitting and not running. Based on the smell and color I'm sure it isn't lower unit oil. Have not been able to start it since I noticed the leak, lower plug is very wet and oily. I'm considering changing the check valves between the oil pump and the injectors. Does anyone know if the pump has internal seals designed to stop the flow of oil when the engine isn't running? I assume the check valves are there primarily to stop oil from being pushed back towards the pump, but maybe they also stop it from gravity feeding into the intake/crankcase. Thanks.

 

[James R]

Re: oil leaking from DT 40

The oiling system is most reliable on Suzuki's. There is no need to change the check valves. They only prevent blow back. Oil will not flow with the engine stopped. The indications you have show insufficient fuel meaning that the mixture is oil rich. Probably time to clean the carb.

 

[botchley]

Re: oil leaking from DT 40

I'm sure it's due for another carb cleaning. I noticed the puddle after the boat had been sitting for months. It's probably dumped three or four ounces at least since I first noticed it, about an ounce and a half in the drip pan since Monday. The motor has cranked for maybe one minute in the last 7 months, never started up. Top plug was wet with gas but clean, lower was soaked in oil. I can't see how that much oil could have ended up in there otherwise, ran ok last time I had it on the water.

 

[James R]

Re: oil leaking from DT 40

Your symptoms indicate that the lower cylinder may be getting all the oil and the upper very little. I have had one case where a tiny amount of dirt blocked or partially blocked a check valve. There is a tiny filter mesh in there and it may need washing out. Try running the motor on 50:1 from a jug or tank and pulling the oil feed lines from the manifold. You should see a weep of oil coming out of each tube. Be careful removing the feed lines gentle is the word. You will need to ease the clips back to clear and then use a small screw driver to pry the lines loose.

 

[Skeeter#2]

Re: oil leaking from DT 40

How interesting, we have a 89 DT75 that did almost the same thing except was only after we pulled the carbs and did a light cleaning inside the bowl, needle valve and such. Ran it with 50.1 in gas tank and found much oil leaked down the outside of the driveshaft housing, but mostly was thru the prop after a run on the muffs. A puddle of oil on the ground after sitting few days. Can say that was my fault to putting the pump link on way too rich. However the #1&2 cycl had heavy oil on the plugs and the #3 looked dry. Something was not right. All three carbs was in sync for idle and mixture setting but now had a fast idle like drawing air leak or something with occasional miss. Do not know for sure. Took her to the Zuki man at that point. cause could not get it tuned anyway.. Says $85 per carb, ouch and will realign the pump to the proper marks. Hope he can explain the #3 plug dry when he is done.

 

[MO Boats]

Re: Oil leaking from my PU40 when not running

Botchley, were you able to diagnose and resolve your problem with unburnt oil migrating out of the exhaust when motor not running and stilling for days?

I have a 1992 Suzuki PU40 with the exact same problem. When sitting in the garage, I get a noticeable amount of unburnt oil leaking out of exhaust vent and exhaust pipe. Note, this is jet and does not have a prop/lower unit.
Does the oil pump have a diaphragm? Could that have a leak, allowing oil to gravity feed from reservoir through cylinders?

 

[saltchuckmatt]

That is a 10 year old thread so don't expect an answer.

Post a new thread with your current problems and you should get some responses.