Suzuki DF100BTX - Lean Burn - Four Stroke 2020 model Making Oil

[CastAway]

My motors make on average 1 inch of oil on each trip. What could be the cause of this and how can it be resolved?
I check my oil prior to each trip and again on the return.
I always check the oil with motors fully trimmed down and when completely cold.
The boat is used for recreationally for fishing. On average i do 80 - 130 NM on a day..
The run to the fishing grounds is +/- 50 NM and takes about 2-3 hours. During this time the motors RPM is on average 4200 -4500 and the speed about 20 - 25 knots
We do some trolling @ 1500-2000 rpm but not more than 3-4 hours per trip, the rest of the time the motors are switched off.
I have 2 x DF 100 BTX 2020 models fitted to my boat. The motors have just under 100 hours on.19" props
Max speed is 35knots at 6200 rpm
My boat fully loaded weighs about 1500 - 1800kg
The boat is a Cat of 6.7m

So far the local dealer has been extremely helpful and changed the thermostats and oil but this has made no change.
He has also fitted 17" props today and i am waiting for good weather so that i can do a long run to see if this makes a difference.

Any other advice or solutions will be helpful

[UrbanBatic]

It could be water or gas:

• If it is water, the old oil should be milky or would have a bit of a water at the bottom of the vessel, when it was changed.

• If it is gas, there are a few ways how this can happen. First just plug out the oil dipstick and smell the hole if you can sense the gasoline (only if high quantity of gas is going to the carter). Also the changed oil was thinner than ordinary 10W-40 if you can recall.

1. Low pressure pump is driven by a mechanism in the block. It may leak the gas directly to the motor.
2. With a lot of trolling the unburnt gas passes by the piston rings and creates oil diluted ...

Do you have the same problem on both of the engines?

[UrbanBatic]

Deleted...

[CastAway]

Hi there, tx for your response.
It is on both motors.
Its not water it is definitely fuel.
What can be done to prevent this. Surely there must be a solution.
On my last trip I did 107NM and only trolled for +/-1.5 and ran @4200 rpm for +/- 6 hours and both motors still made oil
Does anybody know if this is a common problem and what solutions are available?

[Murray]

Another possible source of fuel in oil could be the floats in the VST’s are set wrong allowing too much fuel into the VST. The excess fuel is being pushed into the crankcase via the vent line that is designed to capture fumes. As far as a solution would be to check and adjust the float levels vs specs. As UrbanBatic stated your low pressure fuel pumps could be the culprit but to have both low pressure fuel pumps leaking fuel on both brand new motors seems unlikely. That being said, having both VSTs floats set wrong on two new engines also seems fishy. Maybe fuel is sneaking through the rings but one would think the rings would have “seated” by now assuming the engines were broken in as per Suzuki’s directions. Sounds like your dealer is keen to sort it out so thats a good thing.

[UrbanBatic]

Hi there, tx for your response.
It is on both motors.
Its not water it is definitely fuel.
What can be done to prevent this. Surely there must be a solution.
On my last trip I did 107NM and only trolled for +/-1.5 and ran @4200 rpm for +/- 6 hours and both motors still made oil
Does anybody know if this is a common problem and what solutions are available?

Murray also made a nice point there with VSTs that I didn't give it a thought. The theory with gas going through the rings seems wierd for such a regime of sailing. Usually it's the problem with a lot of trolling.
The VSTs 'problem' is that it's quite a job to get it out behind the intakes, so I would start with the simplest things. Even though I agree with Murray that both LP pumps leaking is very unlikely, it is such a small work to do, that I wouldn't hesitate to cross it out.

Unscrew the guard (2 screws 10mm) and pump (2 screws 10mm head) out the low pressure pump and pump some gas with bulb on the line between the tank and the engine. If the gas is leaking by the pump piston you have a membrane problem. Here is the part of the video what I have on my mind: https://youtu.be/e9cmca3hiIU?t=164 for better explanation.

As the engines are both made at the same time, it may be some wierd production problem, if that is really the case. That is only a wild guess!