I have a early 70's mercury 115hp engine with hydraulic tilt/trim whose
tilt/trim is acting curious.

When I bought the boat last week, the tilt/trim worked great. Drive it
home on the trailer and let it sit for a couple days, try to tilt the
outboard down and it clicks but doesnt go down. So I open the fill cap
and dump a little 10w30 in there (it says 20w, but couldn't find
anywhere that carried 20w and I was told that 10w30 would be fine) A
little dab of 10w30 and the tilt/trim works great.
Up/down/up/down/up/down several time with no issue throughout the week.


So now I hook up the trailer and take the boat to an open lot to
practice backing up (so that I am not tying up the ramp learning how to
back the boat). The motor is all the way up with the little tabs
flipped down to take the stress off the hydraulics (and a ratchet strap
holding everything firmly in place.

After becoming a trailer backing pro, I come home and unhook
everything. I tilt the motor down (seems kinda slow). I try to trim
it back up, and nothing.. I can hear the motor whirrr along, but no go.
I pop the cap and pour a little more 10w30 in ther (cant tell if it's
low since the unit is under the fiberglass seating in the back). No
change!

Any ideas what could be so wrong that it worked, but then stopped after
driving/bouncing around? The fact that motor whirs seems likea good
thing, but I haven't a clue where to go with this next.

TIA guys!

"Arcadefreaque" wrote
So I open the fill cap and dump a little 10w30 in there

Umm, don't those things use some sort of hydraulic fluid?

Nope, its an OLD system. I bought hydraulic fluid first, but then did
some reading (including the label on the pump) and found that older
units used oil and not hydraulic fluid.