Outdrive trim works at idle but not when on plane

LaRea

EDIT:  This problem was caused by faulty adjustment of the trim position sender, not a problem with the hydraulics.  See details here:
https://rinkerboats.vanillacommunities.com/discussion/11835/solved-after-seven-years-outdrive-trim-works-at-idle-but-not-when-on-plane


I suspect a weak trim pump -- looking for suggestions.

One of my Bravo III outdrives refuses to trim up at cruising speeds.  At idle, it works fine up and down, so I know the switches are all working.  But when I get up to cruising speed and try to trim the drive up, it won't move.  My theory is that the hydraulic trim system has enough power to raise the drive with no load on it, but not enough to do it at cruising speed.

Anybody else have this problem?  Should I replace the pump, or try the 18545A1 rebuild kit?  Any chance it's the rams instead of the pump?  

The pump has no visible damage, no history of fluid loss, and no strange noises when I run it at idle.  The rams look fine and are not leaking fluid.  

Thanks.

Dream_Inn

LaRea, I had this issue last year and it ended up being the pump.  Always seems to be the most expensive part.  I went with new, don't know about the rebuild kit.

LaRea

Thanks DI.  Since the pump doesn't have any obvious corrosion or other issues, I think I'll try the rebuild kit and see if it works. 

Handymans342

Mine went up slow and would not go down sometimes so I am changing the pump as well and installing 2 new stainless steel brackets.

Mike_G

Happened to my old Sunsation offshore.... ended up being a pump.  I ignored it at first, but then it went and I couldn't put it up at all!  Yeah.. found out when I went to pull it out of the water (I trailered it) and couldn't because the drive wouldn't raise up to clear the crest of the ramp.    Spent 30 minutes in the water at the ramp disconnecting the trim cylinders and tying it up with ratchet straps before I could leave.    -=Mike G.

LaRea

@Mike_G did you replace, or rebuild?  I'm struggling with $400 for a pump vs. $100 for a rebuild kit that might, or might not, work.

Mike_G

The place that worked on my boat at that time had a newer used pump (looked brand new to me). They charged me $175 for the pump, labor and fluids. Still worked great when I sold the boat. -=Mike G.

LaRea

Update: I bought the pump rebuild kit.  It was easy to install, and I now I'm an instant "expert" on trim pumps.  However, it did not solve the problem.  The pump still won't lift the drive at cruising speeds.

I suppose it could be a weak electrical connection -- unlikely, but easy to check.

After that, I'll swap the pump from stbd to port.  If the problem moves with the pump, it means the pump is bad.  If the problem stays on the stbd side, it means I need to haul the boat and check the trim cylinders.

Black_Diamond

Check the relays too. Two per pump. $20 each.

212rowboat

Check the solenoid, too... The get sporadic. 

rinker312

LaRea. Something is not adding up. It should actually be easier to trim up underway. Are you sure that it is not actually working but maybe the gauge is not working while underway?  Just wondering.  I would try the solenoids next if you are certain that it is not moving. 

Black_Diamond

My solenoids went bad but as stated, sometimes yes, others no. Replace both per pump.

LaRea

Judging from speed, wake and RPMs, I'm certain that the drive is not moving.  Normally, when I start to trim up, I'll see the speed and RPMs rise within 3-4 seconds, and the wake will level out.  Now, even if I hold the button 30 seconds or more, the RPMs never change and the prop never starts to ventilate (which would happen from moving the drive up too far).   

At speed, the trim cylinders see two opposing forces:  the water is pushing the drives up, but the bigger force is the propeller thrust pushing the drives down.  That's why the trim cylinders have to work harder on plane than at idle -- right?  

What's odd is that everything works perfectly at idle, but not under load.   How could it be a solenoid/relay problem?  I would think the solenoids either work or don't, and it's independent of the mechanical load.

(My previous comment about being an instant expert on trim pumps was made tongue-in-cheek ... I obviously have much to learn.)

Black_Diamond

my relay would work and then not.  So they can be flakey, or mine was at least.

rinker312

Good point LaRea. I didn't think about the force pushing them down. So with that being said I still would try the solenoids first just cuz they are cheap and easy to try. But I doubt that will work. Seems to me now that it would be a cylinder problem and you are getting fluid bypassing the plungers. I would have to assume you can buy a rebuild kit for the cylinders.  The only other thing that I can think of would be some sort of pressure relief valve. All hydraulic systems have a pressure relief and if that is failing it would cause the force to hold the drives down. Good luck and keep us posted. 

CPSMARINE

pressure relief valve in pump can stick that is why the pump doesn't brake when you are at full extension or retracted. have to cap off the hydraulic supply with a gauge to see the max pressure. most likely pump if you don't want to be diagnosing the pump output pressure

LaRea

I swapped my balky stbd pump to the port side.  The problem stayed on the stbd side; ergo, it's not a pump problem.  I guess I'll be rebuilding or replacing a trim cylinder or two during my next haul-out. 

A couple things I noticed:

1) When I rebuilt the stbd pump, the fluid that I drained from the reservoir was a thick, baby-puke green instead of the normal clear-brown.  Maybe the PO accidentally topped off with gear lube instead of trim fluid, although it doesn't really smell like gear lube.  (The fluid in the port pump looks fine.)

2) Now that I've swapped pumps, the stbd drive actually will move up *slightly* when on plane, but not far enough.   Below 1800 RPM, it has full range of motion.  For anything above 1800, it will move just enough that I can tell it moved, but not enough to properly trim the boat.

For now, I'll continue using it and just trim up as much as I can.  

Stodge

I hate to say this out loud, but could it be the seal or plunger in the ram?

LaRea

That's my thinking.  I can get a pair of new SEI trim cylinders for $250 plus $200 for a short haul.  (Plus the $80 I already spent on the pump rebuild kit, but I'll call that on-the-job training.)

rinker312

Almost got to be the cylinders now. 

Bizmark

@LaRea. I am having the same issue now that you described. What was your final fix?

LaRea

I replaced the cylinders and nothing changed.  I'm going to replace the pump.

Handymans342

LaRea said:

I replaced the cylinders and nothing changed.  I'm going to replace the pump.

How do you know the drives are not trimming up at speed? Is someone bending over looking? LOL

zaverin1

You don't have to replace the pump
juat replace the electric pump motor
4 screws

Ian

I had the same, motor was dead, shorting across terminals confirmed. Found new pump online and easy replacement - relatively anyway based on working in a boat's engine bay on a hot day.

zaverin1

Pump assembly or trim assembly is made out of 3 pieces 
tank 
pump
electric motor that either Spins cw or ccw 
most of the time it's the motor not pump

Dude_Himself

There's also the trim limit switch. When the pivot bushing/bearing starts to fail it can put lateral tension on the limit switch, so that it fails to activate under load (on a plane).

That would also explain why the problem stays with that outdrive.

jhofmann

If it is the limit switch, the trailer up button should still lift the drive, use in short bursts to see if there is any noticable difference.

LaRea

Replaced the pump/motor assembly - no change.  

So, I have now replaced the trim position sender/limit switch, cylinders pump and motor.  By process of elimination, it has to be a bad solenoid.  

Anybody need a slightly used but known good trim pump?

EDIT:  It was the position sender, not the hydraulics.  Details here:
https://rinkerboats.vanillacommunities.com/discussion/11835/solved-after-seven-years-outdrive-trim-works-at-idle-but-not-when-on-plane 

randy56

Why is it always the last thing you change? Who's law is this? 

Dream_Inn

Solenoid is one of the cheapest parts on your boat.  Oh well, at this point hopefully that is the problem!