trim cylinder issue

DFWcobalt · Tuesday at 10:27 AM

Apologies for resurrecting this one but having a similar issue with my VP outdrive; holds trim on the trailer just fine, but under load the prop thrust pushes her right back down.
Local shop said they couldn't find any leaks, but I can assure you that the outdrive will get pushed down. No oil visible on the drive cylinders, or under the drive when on the trailer.
I suspect the check valve in the pump. Any way to diagnose this with certainty? Would a leaky check valve just allow pressure to escape, or would/could there be a tiny leak somewhere on the pump and oil would go into the bildge?
thanks

Scott Danforth · Tuesday at 10:50 AM

moved your post out of an old thread

you have a leak at the cylinder. its bypassing the piston.

find a different shop, get your cylinders rebuilt or rebuild them yourself.

DFWcobalt · Tuesday at 11:33 AM

Thank you very much!

I'm quite sure the rebuild will be way cheaper than the local cobalt shop asking for 5k to replace the pump and both cylinders!

Lou C · Tuesday at 4:07 PM

I did the ones on my old Cobra a couple of years ago and as long as you can get the end cap off it’s not a hard job. Parts cost was $52 per cyl.

Scott Danforth · Tuesday at 5:11 PM

$75 for a rebuild kit, takes about an hour

If you don't have the pin spanner, it's about $40

DFWcobalt · 2026-03-11T03:55:45-0600

Best source for rebuild kit? DP-SM

Also, how do i bleed any air from the system post-rebuild?

Scott Danforth · 2026-03-11T04:38:44-0600

I use five-stare marine out of Florida

if you look at the link in my sig (near the last few pages), I go thru the rebuilding process.

take care when re-inserting the piston so you do not cut the piston seal.

DFWcobalt said:
Thank you very much!

I'm quite sure the rebuild will be way cheaper than the local cobalt shop asking for 5k to replace the pump and both cylinders!

BTW, that is not a "repair" that is a parts cannon firing parts swap

hydraulic piston seals last about 15-20 years. thats why hydraulic cylinders are rebuildable.

Bondo · 2026-03-11T07:36:26-0600

DFWcobalt said:
Best source for rebuild kit? DP-SM

Also, how do i bleed any air from the system post-rebuild?

Ayuh,...... Just run it up, 'n down a few times, keeping the tank full,......

DFWcobalt · 2026-03-11T07:38:50-0600

Would a pin spanner used to chuck an angle grinder work on the trim cylinder? Seems to be the right size, just not sure how much torque it has to hold to bust the end caps free

Bondo · 2026-03-11T07:53:20-0600

DFWcobalt said:
Would a pin spanner used to chuck an angle grinder work on the trim cylinder? Seems to be the right size, just not sure how much torque it has to hold to bust the end caps free

Ayuh,.... Sounds like it oughta work,......

til it don't,....

Scott Danforth · 2026-03-11T08:33:38-0600

DFWcobalt said:
Would a pin spanner used to chuck an angle grinder work on the trim cylinder? Seems to be the right size, just not sure how much torque it has to hold to bust the end caps free

only if it fits.

this is the pin spanner that I had to use on my VP cylinders. I also had to modify it to fit around the shaft.

Scott Danforth · 2026-03-11T08:39:03-0600

these can work, however are more expensive than the correct ones.

these do not work that well, however I have used them. just takes 3 hands. still more expensive than the correct ones (I got mine on amazon)

I picked up one like the one on the right, then modified it like the ones in the middle.

trim cylinder issue

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