What oil to run in trim/tilt shock absorber?

[62Scout]

'80-something Force 85...been swapping parts around from several motors for years, not really sure what year the trim/tilt system is from. It's the style with the smaller pancake style trim cylinder, one longer hydraulic cylinder for tilt on the right, one passive shock absorber on the left, and pump/motor bolted to the side of the transom bracket.



Opened up the shock to replace the o-rings and wiper, poured out about half the volume of some black oil...Rebuild kit says to refill with ATF, hydraulic oil, or 30wt motor oil, "depending on damping required".

Is there a generally recommended, "for most situations" kind of thing, oil recommended here? Or is this going to be a trial and error thing?

I have plenty of different oils to choose from here, from tuning my rock crawler coilovers, I just have no idea what level of damping an outboard needs.

 

[Nordin]

I have never opened up a shock absorber to refill the oil but the T/T system on Chrysler/Force engines used to need 30Wt non detergent oil.
It depend on the seals if they can manage ATF oil.
I would suggest you to use 30Wt oil.

 

[Mc Tool]

I think the suggested options take into account the ambient temp where its used . Ya wouldnt want to thick oil in real cold temps . I have always used ATF for this sort of thing ........mostly because I usually had some

 

[Scott Danforth]

ATF and SAE 30 are about the same viscosity across the temperature range that a boat is used. your not using a boat in temps below 0 or above 140

 

[Nordin]

If using ATF beware the oil can eat the seals and it starts to leak again.
The T&T require 30Wt non detergent, other multi grade 30W oil will eat the seals.

 

[dingbat]

If using ATF beware the oil can eat the seals and it starts to leak again.
The T&T require 30Wt non detergent, other multi grade 30W oil will eat the seals.

Nitrile is the industry standard for hydrocarbon based fluids.

You will have no issues using nitrile orings and seals with any of the fluids mentioned

 

[Mc Tool]

I recall some oil suppliers promoting an additive called "seal swell " ( self explanatory ) and I have heard peeps saying it works and I think thats what stopped my Guzzi rear drive from weeping ( new seals didnt )

 

[jerryjerry05]

Nordin is right. 30w.