Question for Jon

[James King]

" Jon i have a 75 horse chrysl

" Jon i have a 75 horse chrysler and got it running after carb rebuild but while on the muffs, upper bearing in lower unit failed.i dis-assembled and it had been bad a while.got the new parts,bearing,seal and water pump.installed no problem. i was reading a post about filling the lower unit with oil. chrysler mechanic: from a chart on his wall said 27ozs. o.k. but i had always heard to fill from the bottom until it comes out top hole,well i takes close to 45ozs of oil to do this. this is how i did it. took the boat out on the third day noticed i could smell 90wt. everytime we stopped.well a short time later it let me know it had no oil. got home and pulled drain and nothing but water. take it back apart and the seal under the water pump above the upper bearing had pushed out. bearings and seal were fine so reinstalled seal a little farther in the recess and staked in 4 places hoping to eliminate this again. so my question, did i overfill causing pressure to push the seal out and what if 27ozs is not enough? i know i will find out the hard way on that one,but that bearing cost me $54.00 and i really don't want to do it again. also they call that top hole the "vent" but it does not vent anywhere.so pressure is bound to build up? thanks Jim King "

 

[jon]

" Jim,

I'm just a

" Jim,

I'm just a hack, so I'd check with one of the pro's to be sure, but yes, an excess of lube in the lower unit can cause pressure build up and a loss of seals... have heard of this before, but I allways thought it was more of a theoretical situation. The other thing that could cause this problem is the wrong lube; automotive or just cheap lube will expand when there is power to the lower unit, sorta like putting a whole box of detergent in the washing machine. That would be the first thing I would look into (assuming seal was OK to begin with), what lube is recommended for that lower unit, and what actually ended up in there when that seal went.

As for the "vent", you've got it right, it doesn't do squat, as far as venting goes, when the screw is installed. The vent is there strictly to prevent vacume/pressure while draining and filling the lube, like a vent on a fuel tank.

As for putting in the lube (generally), pull bothe vent screws, drain the old gunk (check for garbage etc).. pump the lube in until it comes out the top, put the vent screw in, put the fill screw in. Now I have one book (seloc for Johnson's) that actually says to top off the vent hole after using an oil can... I think this is wrong DO NOT do it.. seloc for Merc's says to get it up to the bottom of the vent hole, but NO MORE and it warns about recking seals, that's what I've been doing and so far so good. Filling the lower unit half way (27 w/ space for 48) sounds odd to me, but it's possible that 27 ounces is all you need to keep the parts lubed... never heard of this and I can't tell you what's right. Tony can probably tell us for sure, throw a post up that reads "75 HP chrylser how much gear lube? - lost lower unit seal" and hopefully he will be kind enough to offer some advice.

Jon "

 

[James King]

" thank you Jon, i used a hypo

" thank you Jon, i used a hypoid outboard gear oil from advance auto parts 32ozs. while trying to fill probably lost 5 ozs. bought another 10 ozs. tube of lower unit oil put that in still nothing out the hole,bought a 32oz. bottle of 75-90 auto gear lube gl-5 spec and just one squirt it came out the hole,buttoned it up and was fine for 2 days but should have checked it and on day 3 it went. just got a repair manual off e-bay and it tells you to fill until it comes out the top? i would rather overfill than not enough.this time on another mech recommendation i will purchase synthetic from wal-mart and put all 32 ozs. in and if it fails again i go see the man that sold me the parts.Jim King "