4 stroke 150: Tilt stuck up

[webbow]

Went fishing today, and upon reversing the motor would pop-up out of the water at moderate-medium acceleration??
Fished for 8 hours, tilt/trim Went up down all day long.
--Went home, raised motor up, locked safety latch, checked oil reservoir & its full.
--Raised motor a scoot, Unlocked safety latch, motor will lower about 1/2 inch and won't go any lower??
--Unscrewed the tilt release valve (all the way out) and motor will not lower?? When clicking up or down the trim motor sounds like it's doing its normal thing...jut no cylinder movement?
S.O.S...shrugged

[webbow]

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[massbays]

there is a svc bulletin a couple of years ago about this.
they specify a ser # range but I believe it went beyond the stated #'s
only happens if trim is run up to max stop.
repair was to replace some reasonably accessible ck valves.
any dealer should be up to speed on this one.

[EuropeanAM]

If you would, please take a moment to review the Announcements at the top of the Forum, and be sure to provide the Required Info (serial number) when posting. Thanks!

As David indicated, could be relief valves, which are relatively simple to address.

Just to make sure, let's clarify: Was the system ALREADY FULL, or did you add fluid to fill it?

[webbow]

Thanks massbays and Don, much appreciated the guidance; I should have read the bulletin.
After reading the Mercury SB that sounds exactly like what I am experiencing.
My motor serial number is 2B404847, propr 48-825862 21P
I have been experiencing the leakdown for quite some time and just ignored it.
The tilt/trim reservoir was already full when I checked it a few days ago, so that points to the SB as the culprit.
QUESTION:
Does this require a marine shop to perform the SB work? Or can a highly mechanical minded individual perform the replacement of the 2 popet valves?

[webbow]

What's the best way to get the trim to lower?
So that you can remove the trim assembly to get to the back valve.

[EuropeanAM]

Loosen the manual relief screw and if necessary, apply your weight to the gearcase to assist it in coming down. Avoid backing the manual relief screw out more than approximately 1.5 turns.

Accessing the front valves usually requires either removing the engine from the boat OR one transom bracket (while supporting the engine) so that you can partially remove the system.

The later is not really covered in service literature (such as Service Manual).

[massbays]

It's been a while since I've done one, but I think on the 150 you can fully contract the trim cyl and then it will swing out thru the brkt without disassembly.

[EuropeanAM]

I seem to recall that as well... if the engine is supported and the trim functions well enough to get it to move.

[massbays]

I think the 2.1L and 3.0L trim pump will come thru the brkt.

[webbow]

Welp...released the manual release valve, no dice. Took the manual release valve completely out. Tried pressure and left it out overnight and the trim still remains elevated at highest peak.

Vapor lock?

[EuropeanAM]

I'm guessing you have a memory piston or tilt piston that's jammed in the cylinder.

[webbow]

Thanks Don.
I imagined using a ratchet strap from the lower unit to the trailer to see if that would encourage the piston to straighten up in the cylinder... ?

But I'm a hillbilly and should wait to see what you recommend.

[EuropeanAM]

There is no "book" answer as this is not a "normal" situation. Depending on the angle at which you'd be attaching it, this may be a logical method to try.