92 Mariner trim won't hold up

[BJM]

My engine trim has always bled down really slowly requiring me to trim up a little every few minutes or so. This year all of a sudden it can't drive the boat without the motor getting forced down. Sitting still it can lift and lower fine but under a load it gets driven down.<br /><br />The unit is a single cylinder with a motor/pump next to it. What would cause this? I opened it up and found gears, check balls, etc. Is this easy to fix? Are rebuild kits typically available? <br /><br />The motor and pump and cylinder seem fine. I am guessing its a leaky check valve somewhere.<br /><br />Thanks in advance.

 

[BJM]

Re: 92 Mariner trim won't hold up

ttt

 

[JCH55]

Re: 92 Mariner trim won't hold up

I have the same problem with my 40hp Mariner. The trim works, but it slowly goes down. It has been a problem for about 4 years.<br /><br />I did not see any reply to your post.<br /><br />Have you received any resolution.

 

[BJM]

Re: 92 Mariner trim won't hold up

My problem is not resolved. I have ordered a rebuild kit for the pump/motor and I am still waiting for it. No resolution for it yet.

 

[MercMark]

Re: 92 Mariner trim won't hold up

I've got a repair manual for older mercury engines and it says that if the trim leaks down the first thing to inspect is that the check valves aren't being held open by dirt or buildup around the valve seat.<br /><br />...after that you might be into "O" rings in the hydrolic cylinders.... yikes.

 

[BJM]

Re: 92 Mariner trim won't hold up

I've opened up the cylinder and the two pistons O rings look okay. There are 6 check valves in the top piston, I have no idea how to check them. Everything I have opened up looks fine, I guess I will have to change bits until something works.

 

[JCH55]

Re: 92 Mariner trim won't hold up

I found an option from another post.<br /><br />It says " Before tearing apart the trim unit you should check out the manual release valve. It is the large, plastic, slotted head screw on the right hand side of the trim unit. There is a hole through the transom bracket to access it. You can screw the valve all the way out and look at the o-rings on it. If they are cut or damaged even sightly it will allow the trim unit to drop."<br /><br />I am going to try this, I will let you know if it works.<br /><br />If you find anything that works, please post it.<br /><br />Good luck!!!

 

[BJM]

Re: 92 Mariner trim won't hold up

I replaced the O rings in the cylinder so far with no effect. I think its in the pump. I am still waiting for my rebuild kit.<br /><br />Does anyone kow what the pilot valve does? Its stuck in the pump casting in mine and I don't want to frig with it unless it could be the source of my problems.<br /><br />By the way Mariner wanted about $100 for O rings and check balls. I got O rings at a hydraulics place for just under $3.

 

[BJM]

Re: 92 Mariner trim won't hold up

JCH55,<br /><br />Good point about the release valve. I checked mine and the O rings look fine. Also, since I never use it I figure it shouldn't degrade all of sudden like it did.

 

[BJM]

Re: 92 Mariner trim won't hold up

The rebuild kit is in but no change in behaviour. This is a bit depressing. The lacked the various check balls for the system. I guess I will try a bearing dealer and buy some myself.