merc 115 tilt troubles

Hi, Tim here. A fellow brought me this unit and didn't know the exact year of the 115. Its way different from my 1989 model 115. He said that it suddenly quit working. Motor sounds good in both up and down operation. Unit will move if you help it by pulling or pushing it.....but very reluctant and no power. Fluid seems kinda "airated" after running, but clean and clear after a long rest. Fluid is full and no signs of leakage. They never hit anything with the motor and use a support when transporting the boat on the trailer. Any ideas?Thanks again, Tim
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Re: merc 115 tilt troubles

Sounds like an internal bypass (fluid rushing back behind the piston) in the hydraulic cylinder.

Re: merc 115 tilt troubles

That almost looks like one off a Chrysler/Force outboard. Nothing like that ever came with a Mercury. Merc had the 2 ram w/ a pump that was mounted inside the boat (Like those used on the stern drives), 2nd generation was integrated into the transom mounting bracket and used 3 rams (2 for trim and one for tilt), 3rd generation was also integrated into the transom mounting bracket, but used one big ram.

Re: merc 115 tilt troubles

Maybe, I'm still collecting information before I dive into it. Thanks and any ideas will be more than appreciated. Regards, Tim

Re: merc 115 tilt troubles

it is inherent with the design.

every time you lower the engine a small amount of water clings to the shaft and gets inside and sinks in the oil. Over time the water can build up. Also, notice how the paint seems to have dissolved on the bottom but looks new on the top? That is the anodization being eaten away by reverse electro-plating. You need to install a SS strap that goes from a motor bolt down to your anode.

Your problem is most likely the spool valve that is sandwiched between the ram and the manifold. Mercury sells those as a kit. DON'T remove the four bolts holding down the gear plate and rocker arm. If you do then your system probably won't work again.

While you have it apart, you should go ahead and replace the top seal on ram. That's where water gets in. I saw that part once in a mercury parts diagram but can't find it again.

Be careful with the manual release. If you snap off the tip then you may want to have someone else finish the job. It is very hard to get the broken pieces out of the manifold without doing permanent damage.

If you have the time and money then check ebay. You can mail it off to be rebuilt for around $250.

Re: merc 115 tilt troubles

Thanks for the post. I will contact the customer with this info. So this problem can cause almost an immediate failure? I assume this design is faulted, is there an alternate unit that could be used? Thanks, Tim

Re: merc 115 tilt troubles

It looks identical to mine, which is a 96 Merc 115. That top shaft seal isnt available anymore, so if it the cylinders shot the only part Merc sells is the whole unit, which of course is insanely priced. Ive been looking but havent found the seal available anywhere in the aftermarket.

Re: merc 115 tilt troubles

Timguy said:

Thanks for the post. I will contact the customer with this info. So this problem can cause almost an immediate failure? I assume this design is faulted, is there an alternate unit that could be used? Thanks, Tim

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the rust can build up until the spring no longer has enough strength to hold open valve. The failure builds gradually but you don't see anything until it crosses a threshold. Every marine hydraulic system ever made has this flaw. The only way to stop it is to mount the actuator in a dry location. Most systems would have a hose loop or J trap for the water to collect in when the system is stored.

NO big deal. The Merc system goes 15 yearsand has a way better trim motor than most. Look at your picture. That trim motor is almost 20 years old and still going. The cost of a motor is often more than the cost of a hydraulic rebuild. So, it's a wash. Actually, maybe not a wash. Mercury trim wiring is the best in the business - not only the most reliable but also the most affordable. Best in both. At any rate, it won't cost you more than $250 to fix it no matter what. An alternate is going to set you back double or more.

fyrdriver said:

It looks identical to mine, which is a 96 Merc 115. That top shaft seal isnt available anymore, so if it the cylinders shot the only part Merc sells is the whole unit, which of course is insanely priced. Ive been looking but havent found the seal available anywhere in the aftermarket.

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I saw the seal on a parts diagram only a few months ago. It may still be available but the trick is finding the part number. There are hundreds and hundreds of engines & serial number combinations that use the seal. It remained unchanged from 1987 to 2010. If all else fails I sell a seal kit listed on ebay but it may not be the exact parts you want. It's a one size fits all thing.

Re: merc 115 tilt troubles

Great! Thanks, found out that its a 1994 model Mercury. You guys are super, I'll see what the customer wants to do. Best regards to all, Tim