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Need advice on Mercruiser 888 trim problem

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  • Need advice on Mercruiser 888 trim problem

    Thanks in advance to anyone who can help a Mercruiser novice solve a trim problem:Equipment: 1977 Sea Ray Cuddy with Mercruiser 888 (Ford 302) with Alpha outdrive; 3-button trim system with Arco trim pump motor;Problem: Trim works perfectly going up, does not work at all going down (and I've tested this in the water and on a trailer, with the engine running and without). Trim motor itself appears to be working OK (judging by the correct sounds it makes) in both directions. What I've done so far: cleaned all electrical connections, made sure that pump is full of hydraulic fluid; Possibilities: I've read that this model trim system has something called a 'reverse lock valve' that is in-line in one of the hydraulic lines. 1. Would a malfunctioning 'reverse lock valve' cause the trim to only operate in the "up" direction??2. Is it possible that there is something wrong internally with the pump that would allow it to push hydraulic fluid out (and thus make the trim go up properly) but not pull fluid back in and allow the trim to move back down correctly? 3. If the pump is malfunctioning internally, can this be repaired or would it require replacing the entire pump mechanism?I've tried to provide as much detail as I can, but please post questions if it will help someone out there give me some advice on what to try next.Thanks a million!!


  • #2
    Re: Need advice on Mercruiser 888 trim problem

    If the hoses are on the cyls right//front to front and back to back cyls. to hose block you probably have a problem with the cyls unhook them from the rear anchors and see if 1 works and the other don't

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    • #3
      Re: Need advice on Mercruiser 888 trim problem

      I assuming that you filled the pump when the drive is full up? Since you listed you have a 1977 year model you have a Prestolite pump. Check to see if yours has the reverse lock at the bottom of the pump (in the front). Some have a cover over the control knob. Turn knob to the right to release or left to engage. Do not operated the boat unless the lock is engaged.

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      • #4
        Re: Need advice on Mercruiser 888 trim problem

        Thanks for the responses...Laddies, So is it possible to have a problem with one cylinder that controls the downward movement, even though the same cylinder works OK when the trim goes upward ?Trent,No, when I filled the fluid the drive was all the way down. Should I empty it, and then re-fill it with the drive all the way up? And if I disengage the reverse lock, should the drive then go down correctly? And if so, can the valve alone be replaced or do you have to replace the entire line?

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        • #5
          Re: Need advice on Mercruiser 888 trim problem

          So far it just sounds like it might be low on fluid. With the drive up. Check the level and refill. Then see if she goes up and down. If so do it several times and then recheck with the drive all the way up and add fluid if needed.

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          • #6
            Re: Need advice on Mercruiser 888 trim problem

            My '76 888 had the same problem when I bought it. I narrowed it down to one trim cylinder not working properly so I ordered a couple kits and rebuilt both. Works perfectly now and didn't cost too much to fix.

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            • #7
              Re: Need advice on Mercruiser 888 trim problem

              Many thanks again to everyone who's posted advice. Trent, I did what you suggested and filled the reservoir all the way up, with the drive in the full "up" position. Again, the drive would not go down at all. I then noticed some fluid leaking around the base of the port-side cylinder. The starboard (driver's) side cylinder appears not to have any fluid leaking. Would you now suggest taking off the apparently damaged cylinder and seeing if the system will work with just one cylinder? (Can it work at all with just one cylinder anyway??)JasonB, did you actually replace the cylinders with new ones or re-build the existing ones?

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              • #8
                Re: Need advice on Mercruiser 888 trim problem

                I dissassembled and rebuilt them. It's not a tough job, just do it over a clean pan in case you drop something. I used a Clymer manual (not the greates for this task) and had no problems. You just have to be careful since some of the o-rings can be tough to get on and will break if you aren't careful and you have to watch which holes the check balls come out of. Took me about 1hr each and I was really taking my time. The only special tool needed was either a strap wrenches or pipe wrench (careful!) to get the cap off. On the one cylinder thing, It might work at tilt, but I don't think it would have enough power to trim under speed, and I would think it might be dangerous to try due to the uneven pressure under load, you would also have the problem of coming up with some form of spacer to replace the missing ram and plugging the unised lines. Parst to try a repair are cheap. If you are mechanically inclined, you can do it. If not, you can buy complete trim rams for $200.Bleeding them is messy, but not too difficult, just make sure you have a proper flare-nut wrench so you don't round off the hose fittings. A couple seal/ring kits at ~$20 ea (major parts kit is ~$75) and about 3qts cheap 30wt oil for bleeding/flushing/refilling.

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