88 150 help

[Z-man228]

I walked out this morning to find that one of my 1988 yamaha 150's has leaked 2 stroke into my splashwell everywhere. The tank on the engine is close
to empty. It has been stored slightly tilted (less than 1/3 of the way up) so I immediately checked all off my connections, the sealing lid on the sender and and my injection lines to the carbs, all are tight and show no sign of residue or leakage.
I pulled the air breather cover off and all 3 carb banks have 2 stroke oil on the butterfly's and there was a pool of oil in the bottom of the breather housing. I am at a point that I am not sure what to check next or what could cause the tank to drain all of the oil out of it into the carb banks. the keys have been in the house so the ignition has not been on.

any help will be appreciated.

[99yam40]

my thoughts are oil line check valves not holding

[rodbolt17]

either an oil line check valve failed or the oil control module sensed low voltage.
when it hits about 7V the transfer pump turn on.
some folks have had success cleaning the valves in the original pump. some have removed the original valves and replaced them with inline valves some replace the pump with the mikuni pump kit.

[Z-man228]

i dont even know where the oil line check valve is. is that the filter on the remote tank? why/how would it purge the oil from the tank on the side of the engine block? i replaced all of the oil lines last year with new ones that are clear. they are full of oil from the oil pump to the carbs

i lowered the trim and added some oil to the tank on the block (1/3 full) and then turned the key on. the remote tank with the pump filled it right up and shutoff as it should. it is now holding oil level where it should be.

[Z-man228]

I keep the boat plugged into a smart charger so i dont think it would have dropped below 7 volts

[Z-man228]

possible that the small line on back of the oil tank on the block could be sucking the oil and draining it out in front of the carbs when it is tilted up. maybe creating a vacuum inside the small tank on the block and sucking it out when i have it tilted after running it???

[99yam40]

if it was just the motor tank that went low and not the remote tank, then there was not a problem with remote oil pump overfilling the motor tank.
oil check valves should be in the oil pump on the motor or the lines from that oil pump to where they go on motor.
since you replaced the lines with new and did not find any check valves they must be in the oil pump body.

Rod mentioned some people add some in the lines or replace the pump with one that has good valves

[hazmatman]

Similar problem

I had a similar problem with oil in my splash well. Found out it was the manual fill switch module. It was stuck on and always pumping oil. Replaced it and problem was gone. Runs great.

[Z-man228]

i have the old style kein pumps have always worked great. no check valves in line as my understanding was that pump didn't need them. i have had them tilted down all afternoon (about 6 hours now) and the oil level has not dropped. i will check my manual fill but i have never really been able to get them to work since i have owned the boat. i seriously wonder if after running the motors and i bring it home with the motors tilted on the trlr if it created some sort of vacuum and suck the motor tank damn near empty while it was sitting in the garage.????? keep throwing ideas at me i am always wanting to learn more as i normally fish these motors 25-30 miles offshore, they have performed flawlessly for me for over 13 years

[99yam40]

you have aleady been told about the check valves.

[rodbolt17]

on the kien pump the check valves are in the pump cover.

[Z-man228]

IF the Check valves are bad is there enough force from the oil gravity feeding to the pump to cause it to purge out of the Carbs??? Sorry to seem stupid but this is new territory for me. Like I mentioned I filled the tank back up Saturday at 2:00 PM and it was still full as of last night and no mess in my buckets anywhere

[Z-man228]

The saga continues,

While checking over everything I discovered the choke is sticking. The electric chokes never have worked on these motors so I always pull the Manual choke when they are cold. Could the choke sticking have caused something to happen to make the oil tank on the motor drain/purge??

[99yam40]

No, choke will not affect the oil system as far as I know

[Z-man228]

good news is now over a week later and both oil tanks are still full and both electric and manual chokes are working. waiting on a couple of bolts that I ordered that the Mechanic at the local boat fix it shop saw fit to not replace the last time it had carb work done.