Thread: 115 mercury 2003

Originally Posted by Countryboy N.C.

Anybody know what to do to fix the trim on my 115 mercury? when you push hard to load the boat the trim will not hold the motor up, pushes under the boat. Not sure what I need to do? Fluid is good, checked the manual release to see if it was closed and it was.

Not real sure what you're saying ... but, have you checked the trim relays ?? It could be the relays if you can trim in one direction but not the other. If you're trimming the motor up to load the boat on the trailer and it won't stay up, then that's a different story. If that's the case, then here's something I found that may help :

Expert: FieldServiceTech .
"First, when you service the tilt/trim unit, the motor needs to be in the full up position. That will keep the pressurized fluid from puking out the "fill" hole. To service the unit, raise the motor all the way up, use the tilt lock on your motor or a 'block' to keep it in the up position. Then remove the fill plug and add tilt/trim fluid until the fluid just starts to come out the 'fill' hole. Cycle the motor a few times in short strokes to purge air from the system. There really is no secret to servicing the unit. It's not that hard with the motor raised. I use the top of a gear lube bottle, you know the kind with the nipple tip. I cut a piece of aquarium tubing about 12 inches long and placed it over the nipple. Take the top with the hose now attached and screw it on the bottle of tilt/trim fluid. If bleeding all air from the system doesn't solve your problem, there are a couple other things that could cause your system to bleed down. There should be a manual release valve on the side of the unit (probably the starboard side). It looks like a bolt head with a slot cut through it for a straight slot screwdriver. If the seals on the release valve get worn, they will cause your problem and you will need to reseal the valve. The only other thing that could cause your symptoms are worn piston seals on the tilt rams. If this is the case, you'll have to pull the unit apart and reseal it. " (copied in part from https://www.justanswer.com/boat/25rh...old-motor.html )

Mercury Marine 115 HP DFI (3 Cylinder) (1.5L) Power Trim Components Parts

This is for a 115 3 cylinder. If you page back you can put in ser number and look at yours. If this is what you have I would say either seals on lift piston are leaking or one of the poppet valves is leaking. If you have trouble with this just post model number and serial number and we can figure out where to start you.

Originally Posted by Countryboy N.C.

Anybody know what to do to fix the trim on my 115 mercury? when you push hard to load the boat the trim will not hold the motor up, pushes under the boat. Not sure what I need to do? Fluid is good, checked the manual release to see if it was closed and it was.

are you saying when you come in from fishing and loading the boat , when you drive on the trailer and gun it a little the motor drops ???? if that is the case you have the motor trimmed too high !!!

Originally Posted by Cray

Mercury Marine 115 HP DFI (3 Cylinder) (1.5L) Power Trim Components Parts

This is for a 115 3 cylinder. If you page back you can put in ser number and look at yours. If this is what you have I would say either seals on lift piston are leaking or one of the poppet valves is leaking. If you have trouble with this just post model number and serial number and we can figure out where to start you.

Well I talked to a boat shop, he thought it was the seals on the piston and he is going to order me a set of seals. It is a 2003 115 ELPTO OT734019

Couple of questions. Is this a problem when trimming the motor while running across the lake? Does the motor not hold a "tilt" or "trim" position when left alone?

Originally Posted by sliderman

Couple of questions. Is this a problem when trimming the motor while running across the lake? Does the motor not hold a "tilt" or "trim" position when left alone?

It only goes down when under a lot of pressure , like loading on trailer, pushing it on, or running down the lake wide open it will settle some. I know something is leaking by, fluid is leaking by something, thats why it settles down.

I have one that does the same thing if I trim it up much when loading it only.but It will stay trimmed when I’m running or just setting around .don’t drop at all

If I am understanding you correctly, there is not a problem with the system. I'll give a brief description of how the system works and let you decide.

By design, from a full down position (neg. trim angle), to perhaps 15* of positive "up" angle, the hydraulics work (and hold) at a high pressure value that is needed in order to "trim" the motor while under a heavy work load. As the ram extends beyond this point, a relief valve in the system is exposed and allows the system to bleed down (at a lower pressure value) until the valve is no longer exposed. This portion of the system is referred to as the tilt function.
With that being said, if you trim the motor above the "trim" circuit while idling around and then apply throttle, the motor will over-ride the 'tilt' circuit and come to rest at the top of the "trim" circuit.

Not everyone is familiar with how the system works and it's not uncommon for owners to believe that something is wrong when it happens. As you can see, someone chimed in describing the same thing.