Fuel in oil problem.

Reposado 1 · Feb 15, 2022

I have a 1997 2520 with 102 gallon tank and an inboard merc 383 with bravo 3 outdrive. I bought a brand new 383 from Merc in August of 2021. Not a remanufactured engine. It immediately statred getting gas into the oil, which we could see easily as it measured higher on the dip stick. Changed the oil three times and attempted to break in the motor as per merc recommendations to the letter. Still got gas in the oil. merc sent out another brand new motor which did the same thing!! The dealer is flummoxed and out of ideas. merc is out of ideas also. has anyone had this experience with a 383 or heard about a current problem these engines are having? Thanks.

big_tuna · Feb 15, 2022

these are simple questions and you've probably gone over these already, but have you checked the thermostat? If the engine is running cold all the time, it's possible some unburnt fuel is leaking past the rings. Also, if you are running rich, (is it carbed?), you can get excessive fuel in oil as it's just dumping unburned fuel into the chamber and leaking past the rings.

Reposado 1 · Feb 15, 2022

big_tuna said:
these are simple questions and you've probably gone over these already, but have you checked the thermostat? If the engine is running cold all the time, it's possible some unburnt fuel is leaking past the rings. Also, if you are running rich, (is it carbed?), you can get excessive fuel in oil as it's just dumping unburned fuel into the chamber and leaking past the rings.

Hello Big Tuna. Temps are perfect and it's MPI. No evidence of running rich. It's really a profound mystery. And extremely frustrating. Voltage is perfect, fuel and oil pressure all show perfect on the merc smart tach. dealer also took detailed readings during sea trials with his laptop and sent results to merc. everyone is scratching their heads. Thank you for picking up my question. Just thinking outside the box now: anyone ever heard of this happening with this i/o model of Parker? Fuel tank is venting properly. Even if it weren't, the engine would starve for fuel. Voltage is correct. Hard to imagine it's something to do with the boat, and no one around here thinks it is, but maybe someone out there in Classic Parker Land knows something? Thanks

jamesd156 · Feb 16, 2022

check the fuel pump if it's manual and drives off the cam bad diaphragm can cause that

Reposado 1 · Feb 16, 2022

jamesd156 said:
check the fuel pump if it's manual and drives off the cam bad diaphragm can cause that

Thanks for your reply. Yes, the diaphragm design was a point of failure that would lead to this problem. But that is a pretty old technology at this point. These are 2021 and 2022 engines with electronic fuel pumps. I wish it had been manual pumps, but no. Happy boating.

big_tuna · Feb 16, 2022

Reposado 1 said:
Thanks for your reply. Yes, the diaphragm design was a point of failure that would lead to this problem. But that is a pretty old technology at this point. These are 2021 and 2022 engines with electronic fuel pumps. I wish it had been manual pumps, but no. Happy boating.

You could check fuel pressure