Jughead135

Outdrive suddenly won't come all the way down

14 posts in this topic

Out enjoying the lake today--everything working normally, including the power trim as recently as about 5 minutes before I got back to the no-wake zone by my dock (was full-down as we passed through another no-wake zone).

Went to idle as we approached the dock, trimmed down (or, "tried" to trim down), but the gauge will only go to about 3/4 down (indicating just a bit over). Once up on the lift, I played with it a bit more--it goes all the way up, but gets there way too quickly (i.e., shorter distance to travel); "trailer" position seems to be all the way up as well, with the same caveat. Going down, however, is strange. It stops at the 3/4 position (by eye, seems to be just a shade above level, with a couple of inches to spare on the pistons), and it makes the same noise it normally does at the full-down position (slight "clunk," followed by change in pitch of the trim motor as it tries to push it beyond the stop).

Ideas??

Thanks!

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Clunks are not a good sign in a hydraulic system.

Down should work the easiest due to gravity helping.

Get some professional help.

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The clunk refers to the drive hitting a physical stop, not the hydraulics themselves. That's normal, no?

Otherwise, agreed, gravity should be helping, and since I'm scratching my head right now, I'll need a mechanic's touch....

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Sounds like a trim sender unit problem to me. Not sure about Bravo units but on an Alpha unit you have one either side of the gimble bearing area. One does trim up and down the other trailer. Might be worth a look...

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Sounds like a trim sender unit problem to me. Not sure about Bravo units but on an Alpha unit you have one either side of the gimble bearing area. One does trim up and down the other trailer. Might be worth a look...

Just to clarify, the left side unit is your trim Limit switch which when adjusted, limits how high the out drive comes up when using the trim switch on the dash to protect it from trimming too high when operating.

The right side switch is the trim Sending unit which sends the signal to the gauge on your dash as to out drive position.

The limit switch is adjustable and if it has moved, it could possibly make the system think its all the way down when it actually isn't.

Both units operate on resistance of current flow over a series of electrical strands to determine location. These strands can wear out and give false reading to prohibit movement.

These are sealed pretty well but if water gets in these, don't expect them to work right.

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+1 on the trim sender unit circuit. Mine acted up a little this year, was getting false readings. I cleaned the quick connects in the engine compartment and tightened up the connections. That corrected my issue as they had developed a little bit of corrosion/tarnish on them and were a bit loose. Next option would be to put a mark the actual sending unit switch to show where it now and then try adjusting it a little to see if it will allow the outdrive to lower a bit more then it is now. Going to have to have the outdrive swung to the starboard to access the adjustments screws as the switch is mounted to the gimble ring which sits inside the transom housing. Keep us posted.

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Thanks for the comments on the trim sender unit. I speculated on something like that, but here's my question:

Going "up," the motor just stops when it hits the limit--the limit switch evidently acts as a cut-off upon reaching the full-up operating position.

Going "down," the motor keeps running as long as I hold the switch. The sound of the motor has a distinct change in pitch when it hits the limit, as if the motor is trying to push the drive "past the stop" but is mechanically prevented from doing so. This has been the case all along when the drive reaches full-down. However, it's also the case now, except the drive is not reaching all the way down. Is there some sort of (adjustable) physical stop in there that could have become maladjusted (and in the space of a single drive movement)...? Otherwise, what would stop the drive from moving, at a consistent point, before it reaches full-down with the trim motor still running and making the same noise it makes upon reaching the full-down position?

There's a very large chance that I simply don't understand the finer points of how the power trim works--please continue to educate me!--but, that's why I'm having trouble thinking it's a simple electrical switch issue....

Unfortunately, we had to come home yesterday--won't be back to the lake for a couple of weeks to try our hand at getting this resolved.... Thanks for the help!

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+1 on the trim sender unit circuit. Mine acted up a little this year, was getting false readings. I cleaned the quick connects in the engine compartment and tightened up the connections. That corrected my issue as they had developed a little bit of corrosion/tarnish on them and were a bit loose. Next option would be to put a mark the actual sending unit switch to show where it now and then try adjusting it a little to see if it will allow the outdrive to lower a bit more then it is now. Going to have to have the outdrive swung to the starboard to access the adjustments screws as the switch is mounted to the gimble ring which sits inside the transom housing. Keep us posted.

In this case it's not the sender unit as he isn't getting false readings, he's not getting the drive itself to drop down. I would focus on the left side limit switch, not the sender switch.

One other thing you might check are your hydraulic seals. Look very closely at the end of both pistons. When these seals go bad, you can sometimes see the seal rubber squeezing out along the rod.

I've known these to go bad and inhibit the full extension of the out drive. Your hydraulic oil can also be a sign as it will be milky white due to water intrusion.

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You are correct Bob, I was under the impression the unit was going down all the way but gauge was saying otherwise. Let me start by asking how involved you want to get in this Doug? If you want to try and rule things out and see if you can save some deer, start by checking your hydraulic fluid level & condition and then inspect around the hinged portion of the lower unit where the gimble housing pivots in the gimble ring to see if there is an obstruction anywhere in the area. Also look at the exhaust and shift bellows to make sure they are not damaged. Do this with the boat on your lift and while someone else lowers/raises the unit (please be very careful and make sure the other person is mature enough not to run the unit unless you say so). This way you can see exactly where the hang up is occurring. Like Bob said, also check the cylinders themselves for possible internal binding or a bend shaft. If in doubt, you can disconnect them from the lower unit and see if they both operate to full extension/retraction with the outdrive disconnected and stationary. If they do, then go back to the outdrive with them off and rock the lower unit slowly up and down to see where the hang up/binding is happening. If I remember correctly the trim limit switch (port side of gimble ring) only controls the up limit. I say this because when you begin the calibration process on the limit switch, the outdrive unit is suppose to be all the way down and then you turn the limit switch along with the up toggle until you reach the desired up stop limit. There is no down stop calibration other then the initial starting point being with the outdrive all the way down (someone correct me if I am wrong please). If after all of this, you still have not found the issue I would turn her over to the pros and bite the deer bullet. Good luck Doug.

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Fixed! (mostly...)

My search found me several ideas, but here are the two that counted:

http://forum.chaparralboats.com/index.php?showtopic=14863 [not sure how I missed that one the first time around, this board is where I started looking!]

http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/97mercruiser-alpha-outdrive-5-7-ltr-wont-trim-down-568240.html

Apparently there's a pressure-operated check valve involved with the mechanical limit of travel (all the way down, or all the way up in the "trailer" mode). That valve can evidently stick in such a way that it mimics the full-down position. Those two links got me thinking that it was the issue, since they exactly describe the problem I was having. Before I started jumping on the outdrive as suggested in one of those links (and I decided at the start that trying to extricate the valve and/or bleed the system was more than I wanted to bite off on), I called the shop I use to ask if it's something they've seen before....

I learned:

- not exactly "common," but it happens, most typically after a long storage with the outdrive up (good to know--no one ever told me I'm supposed to lower the drive on the trailer!)

- the valve in question is an integral part of the pump; valve failure fix = replace pump ($$$$$!!)

- suggested fix: take the boat out, put it under enough power to get the bow up but not enough to plane, then cycle the trim up a bit, then down--repeat several times.

That suggested fix worked in my case! Third cycle, the trim ran all the way down. Deer expended: zero; tools used: none; admiral approval factor: high. I did some running around (purely for testing purposes, you understand!), cycling the trim up & down. It stuck one more time on me, in approximately the same place. Same fix released it....

Thank you to all who helped here (and in the other thread). I'm left with the obvious follow-up questions:

- Is a pump replacement really the only way (or only economical way) to fix this valve? That would seem to this layman to be a really poor design....

- Is this just "one of those things," or is my boat telling me it's getting sick and this is going to fail on me altogether sooner rather than later?

- Any problems with running this to failure? Seems like this won't strand me on the water--might make for a really, really long trip home if I have it trimmed too far up for running conditions & can't get it down, but I shouldn't be stuck in the middle of the lake.... Yes/no? On Lake of the Ozarks, I frequently run with it all the way or most of the way down, anyway, due to the rough water on busy days....

Thanks again for all the help/advice/interest!

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Have this same problem. I'm going to start by cycling the drive up and down and seeing if that fixes it. Then I will check/add fluid if necessary. Then I will apply pressure as I trim down and if that fails, I will bleed the system of air.

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First of all the trim limit sender is in the trim up circuit only, and will never prevent trim down even if you cut the wires off the thing. Secondly the internal check valve referenced is actually an over-pressure relief valve. Your trim pump is a positive displacement high pressure unit and when it's running, oil has to go somewhere. If the drive is full down against it's mechanical stop, then the pump labors, and forces open it's internal pressure relief valve giving you a chance to get your finger off the button. What happens over time is when a drive is stored in the up position, the wiper ring situated just outboard of the trim cylinder shaft seal begins to corrode. This does not seem to be an issue with drives stored full down, as the ring is constantly submerged. I say this as I've only seen this problem when boats are stored drive up or on lifts and an owner keeps the drive full up in an attempt to keep more of the drive out of the water. Over time the wiper ring corrosion grows between the wiper ring and aluminum cylinder end cap to the point where it pushes the ring inward and grabs the shaft so tight, the trim pump can't lower the drive. It's amazing how tight the hold actually is as I've needed to use a 20 ton hydraulic press to get the end cap off of the shaft during rebuilds. At times the distortion is so bad that the end cap requires replacement. MERCURY MARINE 25-87400A2 Seal Kit

My message is this. Your pump is fine, and the proof of that is that it is able to raise the drive, even under power which on a healthy system is much more difficult that lowering the drive. Yours is a mechanical problem, and the fact that you got her to break loose once is no guarantee that the issue won't return. While the thing is moving, I would attempt to figure out which cylinder is currently the bad actor through careful visual inspection, and throw a $15 seal kit at the thing before it locks up again. The repair is really straight forward and we would be happy to talk you through it. The only real trick is to fill the cylinder completely on both sides of the piston during reassemble so as to ease the bleeding process. This is best done with the cylinder on the work bench. New OEM cylinders are actually shipped pre-filled and plugged. W

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+1. Wingnut. Also remember, The pressure relief for UP pressure is about 5 times that of down pressure relief. 2500 psi versus 500 psi. If the cylinders are beginning to seize, it will be first noticed on the downward motion stalling.

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Mine did that once, trimmed up and then wouldn't trim down. All it was, was a bad wire connection in the remote throttle assembly. Redid the connection and everything was fine.

Don't know if this will help, but it might be just that simple.

Btw...I am by no means a mechanic and claim absolutely no expertise, just stating a possible fix.

The dumb question, is the one not asked.

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