88' Force 85hp lower unit oil viscosity

[DunbarLtd]

I bought some SAE 90 Quicksilver and have been running it in my lower unit this year. Only been out 3-4x so far. I dont know if it is coincidence or the oil is the cause but I have a high pitch whine when at cruising speed. Matches the frequency of my tinnitus lol.
Anyways, it seems like its coming from the engine area. Last year I rebuilt the lower unit and replaced the upper bearing on the drive shaft. I am only guessing here but it is possible the SAE90 is too thick when cold and not lubing the upper bearing? It seems to go away after a while running around the lake. From what I read the 80w-90 is only to be used for 75hp and LOWER? Is this correct? What should I be actually running?

 

[racerone]

Is the oil level correct ?----Filled from bottom til oil came out the vent ?---Did you do any shimming to make sure you have correct tooth contact?----Or just installed the shaft and closed it up ??-----I don't think that oil is the issue here.

 

[topgun3690]

My manual says to use SAE90 in my older 85HP.....should be the same.....

 

[DunbarLtd]

Is the oil level correct ?----Filled from bottom til oil came out the vent ?---Did you do any shimming to make sure you have correct tooth contact?----Or just installed the shaft and closed it up ??-----I don't think that oil is the issue here.

Well this is something that developed some time after rebuilding. It didnt happen right away. Almost seems like it started after I switched to sae90. But again could just be coincidence.

What happened is I had a clutch dog tooth break off because I think I had slop in my linkage. Which I have corrected since then. I hit reverse to slow down while at idle and the lower unit locked up instantly. No grinding or anything just sudden lockup. I was super lucky it didnt damage any gears. I did remove them both and inspected which lead to the "rebuild". While I had it all apart I changed the driveshaft bearing. Made sure it was pressed all the way down. I used the original shim for the driveshaft bearing and switched out the clutch dog and use all new seals and pressure tested for leaks. Also torqued the pinion nut down to spec.

Also properly adjusted the shift linkage. It shifts fine now with no clatter at all in forward/reverse. Lowered the idle a bit to take some of the stress off it as well. I did not paint the gears to check tooth pattern. I may still need to do that to rule that issue out. This issue just sort of popped up last couple times out. Could be that replacement bearing either prematurely wearing out or not getting oil, could also be anything. It doesnt sound like gear whine. I know what that sounds like. Its like a very high pitched squeal, almost sounds electrical if that makes sense, its not like a grinding squeal.

Yes I filled it with the sae90 until it came out vent. Then waited 30 minutes. Spun the prop a bunch of times. Did that process 3 or 4x and let it sit overnight on the last fill and it was still full by morning. So closed her up and ran it.

Whats weird is it goes away after running almost like the oil thins out but that is just my hunch.

 

[jerryjerry05]

I fill from the fill and vent holes.
That way there's for sure enough oil in there.

 

[topgun3690]

I fill from the fill and vent holes.
That way there's for sure enough oil in there.

Same here......

 

[racerone]

Filling from the bottom drives all the air out.

 

[DunbarLtd]

I also fill from the FILL hole. Not really sure how I would be able to fill from the bottom. That hex plug is tiny. That would make more sense though. I will be trying to top it off today without removing drain plug and just see if I can get anymore in there. At least to rule that out. I am going to try and get video of the whining. Hopefully, I will be able to hear it on video. So many different types of noises with outboards, Im sure its quite difficult to diagnose without hearing it.

The only other thing is I am getting a vibration when cruising. It seems to settle a little at lower speeds. I have another prop at home Ill be trying and I put a dial indicator on the prop shaft and its less than .003 so Im not suspecting its a prop shaft issue.

Can engine issues cause vibration (mainly feel it on the floor with my feet). I dont know if the two are related or not but just thought Id throw that out there.
Lastly I have to adjust the "trim tab" exhaust snout a little bit because last time out I made sure my trim was set correctly while at cruising speed. I trimmed UP as far as I could until it started to porpoise and then DOWN until it smoothed out. When I got it to the right level, I noticed the boat tugging to the left. So I am going to adjust that snout a hair. Also not sure if that would cause vibration or not. Other than that, it starts fine. Idles fine with needles one turn out. Definitely scratching my head when it comes to the whining.

 

[airshot]

Have you changed the lube recently to see if there are any metal chips in there. Metal chips can cause a whine..well worth a quick drain and fill to check !!

 

[Nordin]

I have worked with outboards in 25 years, not for living but in free time with all different brands such as Merc, OMC, Chrysler/Force and all Japanese and generally you always fill the gear case with oil from the bottom (drain hole) and up until oil weeps out at the (level) vent hole.
OEM service manual OB4642 for Force 85, 90, 120 and 125Hp 1988 thru 1991 has two different methods to fill the gear case.

One piece driveshaft: Fill from fill hole until oil weeps out vent hole (both holes are at the top of the lower unit, beside each other). Close the vent hole with the screw and remove the oil nozzle and close the fill hole with the screw. Open the vent screw and let the lower unit stand in upright position for one-half hour to allow trapped air to escape.
Then recheck the oil level and if necessary add oil.

Two pice driveshaft: (All three holes open) Fill from drain hole until oil weeps out the vent hole. Close the vent hole and continue add oil until oil weeps out the fill hole. Close the fill hole and the close the drain hole with the screw.

 

[DunbarLtd]

I have worked with outboards in 25 years, not for living but in free time with all different brands such as Merc, OMC, Chrysler/Force and all Japanese and generally you always fill the gear case with oil from the bottom (drain hole) and up until oil weeps out at the (level) vent hole.
OEM service manual OB4642 for Force 85, 90, 120 and 125Hp 1988 thru 1991 has two different methods to fill the gear case.

One piece driveshaft: Fill from fill hole until oil weeps out vent hole (both holes are at the top of the lower unit, beside each other). Close the vent hole with the screw and remove the oil nozzle and close the fill hole with the screw. Open the vent screw and let the lower unit stand in upright position for one-half hour to allow trapped air to escape.
Then recheck the oil level and if necessary add oil.

Two pice driveshaft: (All three holes open) Fill from drain hole until oil weeps out the vent hole. Close the vent hole and continue add oil until oil weeps out the fill hole. Close the fill hole and the close the drain hole with the screw.

I have the one piece drive shaft. So I fill from top until it comes out vent.

 

[jerryjerry05]

Yes then fill from the vent till it comes back out the fill.
Repeat until it won't take anymore.