after about a 10mi run back to the ramp today shift my boat to neutral and hand it off to my fishing partner to load he then stated would not go in to gear??? feels like its i a bind so we loaded the boat with the winch get back to house i remove the motor cowling check the linkage seems to be all hooked up i am get some what of a Oder of gear oil so i decide to check the gear oil so i remove the top plug seems to be full i then remove the low water pickup screen a proceed to remove the drain plug a and gear sprayed out out 10 ft or more both of covered in gear oil we are like wtf anyone ever experience anything like this and now the sifter works as it should... any help would be greatly apreciated

Wow..they must be some good seals in that Lower unit. Yes, I've had pressure build from being overfull, but that usually will blow out a seal (Mercury). I always fill my lower unit, take it out and run it for 10 minutes or so, load back up, and crack the top screw to let any pressure and excess oil out.

Gman

You would think any pressure would have been released when you opened the top screw. Never heard of anything like this.

You will have some pressure in the lower unit right after a run. That is the reason to not over fill. 3L Mercs were bad to blow out the main shaft seal if you put over 32oz`s in them. They came out with a HP seal held the seal down with bolts.

you have a major problem in the gear case oil got hot and created the high pressure

Why do you think lower unit oil gets black? Heat. I tested a 250 Yamaha today. As soon as I got the boat out of the lake I stopped got out and could not keep my hand on the lowers bullet.

i refilled with new gear oil ran on the hose a few took it back lake ran it hard for about 15min load and went home a removed the drain plug same results spray gear lube about 10 ft or so. the lower unit was just replaced about year and half with a new yamaha oem unit i changed the oil in the unit back in the spring i was give the yamaha hd oil witch just found out not to be the correct oil... hope this was not the cause

of course a lower unit bullet part is hot after you take it out of the water the hot exaust and water is going through the rear half of the bullet of the lower unit but the gear oil internally should not be getting hot

Interesting. I have never had a bullet on a motor hot to where you couldn't touch it. In our old omc the lower unit lube never turned black either.

In the merc it did turn black, but never noticed it get hot to the touch.

I don't know how there was pressure to shoot stuff out the bottom under pressure with the top screw already removed.

the fist time it did it the boat had been out of the water at least 2hrs towed probly at least 40mi ... the oil i could have maybe been warm to the touch but not hot blew out just like boiling radiator on a car i was covered head to toe. i have a video from the second time i will tryn post it later stood clear this time. lol

If you drop the lower unit, check and see if the exhaust tuner is burnt out. I don't know if that would cause your problem but I do know these motors are bad about melting the tuners.