Bravo 3 trim strangeness...
 

The boat:
'99 Formula 330 SS
Dual Merc 454 L29 engines (SN: 0L34xxxx) w/ about 400hrs/ea stock
Bravo 3 outdrives, rebuilt two years ago
26P props

I've been trying to work out some power issues where I'm not hitting the speed/RPM I expect and I keep running into a strange drive trim issue. I want to get this fixed before
I proceed with anything else.

Port outdrive: During the original survey it was noted that the port drive will trim all the way up/out when using the trim switch, as if the trailer switch is being used. My guess here is that one of the previous owners rewired the trim switch to the trailer switch in order to bypass a bad trim limiter. Is that possible? Since the drives were rebuilt in the fall of 2011 I expect them to have all new limiters so if this is the case I should be able to undo the "hack".

starboard outdrive: This one is a bit more tricky. The trim works perfectly fine at idle/low RPM, but if I start with it all the way down/in and get up to more than about 2000RPM, it seems to get stuck in the in position and refuses to budge unless I first slow the starboard engine down. Once it's been moved even a tiny bit up/out it will have no problems unless I bring it all the way back down/in, at which point it gets "stuck" again. When it gets stuck it actually acts like it is an electrical problem since I can't hear the hydraulic pump run when I try pushing the switch forward. Also the trailer switch acts the same way in this case.

I've done tons of searching, but somehow I have two issues that I haven't found mentioned anywhere else, hopefully someone here can help.

Thanks,
Dan

Some added information.

I tried to move the drives via the trailer switches today, the results were disappointing, the port drive would trim down only, anything else was totally unresponsive. I don't remember this being the case last year. Also, the starboard drive was being intermittent while trying to trim up, so I'm starting to think the problem is in the switch... The only thing is when I have the drive all the way down and I'm under way, it ALWAYS refuses to move (or even try) until I slow that engine down, then it ALWAYS works again.

I've spent the last few hours reading on the wiring of the trim switches, it looks like I'm going to have to go through the harness wire-by-wire to figure this out.

If anyone has ANY suggestions or can suggest ways to increase responses to this post, I would LOVE to hear... As is, I fear my strange trim problems have even the best people here stumped, in that case I might have to take it to a Mercruiser facility and throw money at them until it's fixed. :-(

Okay, since I'm still not getting answers and my problems seem broad, let's start with the most critical problem, and the one that I don't even know where to start with troubleshooting...

The starboard outdrive: Drive will only trim up from full (100%) down position when the RPMs are low, but once it's trimmed up even a touch, it will go up and down all day at any engine speed unless I go back to 100% down, where it gets stuck if the RPMs are high.

Keep in mind while thinking about this that it's entirely possible that the previous owner had moved wires around, I'm still trying to trace everything to confirm this has/hasn't been done...

Yes it's possible. On the inside of the boat along the transom area there should be a purple & white wire and a blue & white wire in close proximity of each other. They go to the trim limit switch. if they are joined together with a jumper wire then that would explain the trim switch going all the way up like the trailer switch. There should be two black wires plugged into them coming from the limit switch.

If only the "stern drives" were rebuilt and not the transom housing assemblies then having new trim limit & gauge switches would not be a normal repair job unless otherwise specified to the service writer. Do you have your invoice? You should see Merc part #805320A03 for about $101.25 if OEM parts were used.

This issues sounds more of a mechanical problem vs an electrical problem to me.

It's possible that one of or both of the trim rams are bent, have corrosion on the end caps not allowing the drive to move up from a certain point due to the binding up pressure from being at speed, The inner trim rams connecting ends may be turned 180 degrees out from last servicing, or the celery stick is in the wrong position from last servicing. The rams may need to be rebuilt or buy new ones depending on condition or It could also be a hydraulic problem within the trim pump valves. Pressure testing the trim hydraulic system would be the only way to confirm some of these hydraulic theories.

Try adding a good amount of something like blue wheel bearing grease to the trim rams while running the drive up and down a few times to see if that helps prevent it from becoming stuck.

If the mechanical portion of the drive gets stuck then the trim pump motor would have a different lower pitched sound to it as the hydraulic portion of the trim system would not be flowing correctly possibly making it harder to hear. Typically speaking, usually a stuck trim ram does not interfere with electrical portion of the trim system unless the trim limit switch is misadjusted or internally corroded just enough so that once the ram is tucked in all the way.... in that one certain spot, the limit switch could be limiting power to the trim pump motor not allowing the drive to come up until you slow down allowing the drive to rest down just enough to allow the limit switch to work again. But this theory is unlikely because the trailer override button should allow the drive to come up.;)

Do you have a copy of stern drive service manual number 11? The info mentioned above can be found in service manual number 11.

The link below will help show you the correct position for celery stick installation,
http://www.boatfix.com/merc/Bullet/98/98_16.pdf

Thanks a ton for this info, I do have the service manual but I found it difficult to use for troubleshooting, I didn't see any section for that sort of thing. I might have missed it though.

After reading the suggestion about the problem being mechanical a light bulb finally let off a dim glow in my head... This makes perfect sense, I think one of the trim cylinders actually took an impact at one point, during the survey when I bought the boat it was noted that the port-side trim cylinder on the starboard drive was missing the bolts for the zinc anode, I'm guessing those were sheered at the same time that things got slightly tweaked. I'm going to try the grease suggestion but I think it's time that cylinder was rebuilt/replaced (on a side note: do you have any information on rebuilding them? I couldn't find anything specific).

I looked over the receipt for the drive rebuilds and it doesn't say anything about trim limit/gauges, so I guess they weren't done after all... disappointing. With that said though, the trim gauges work perfectly (although one needs to be adjusted) and the limiter works fine on the starboard engine. My understanding is that if the port engines limiter is fried then the drive won't go up at all, hence my speculation of a rewiring hack. After thinking about this a bit more I was wondering if it was possible that the adjustment screws for the limiter had just been removed or come out due to vibration. In this case the limiter would just rotate as the drive went up, right? I know this is a bit of a long shot... I need to do a lot more digging to rule out the wiring though.

I know I need to check the hydraulic pressure on both sides, but DAMN that gauge is expensive, at least for something that will most likely be used once. I found it for $250 on ebay... Still probably cheaper than paying someone else to test it.

Thanks again, you've been a HUGE help!!!

:)In service manual #11, you will want to read sections 5-B Pages 10 - 18 for the trim ram assembly rebuild procedures. Take special note of bottom of page 18, it shows you the correct way to place the trim rams and inner trim rams. This is in reference of the 180 out I mentioned above.
http://www.boatfix.com/merc/Servmanl/11/11b5r5x.pdf

Section 5-A Page 5A-52 will show you a wiring diagram of the trim system with the trim limit switch.
http://www.boatfix.com/merc/Servmanl/11/11a5r5x.pdf

If you do decide to rebuild the trim rams, the OEM seal kit & I believe the overhaul kit comes with detailed instructions on how to do it. It's the same info that's in the Manual.
http://www.mercruiserparts.com/Show_...der+Components

But if you find the inner ram is bent, then you're going to need to buy a new ram as Mercruiser does not offer the inner ram separately.

Here's an bravo parts catalog to look up the OEM parts & numbers,
http://www.mercruiserparts.com/selec..._nbr=809808+96

If you find that you need a new ram and are on a budget then there is an lower cost alternative from sterndrive engineering.com,
http://www.sterndrive.cc/mm5/merchan...rTrimCylinders

Also (in my opinion) you should always find and google/ebay the OEM part number to ensure your getting the best deals available with any parts you buy online.

This depends on what you mean by "At All" plus on how you're using the trim system.

With the drive down far enough for normal running mode, using the trim up only button, the drive would come up to a set height then stop due to the limiter, then at the helm area there should be an additional override button/switch called trailer that will bring the drive up the rest of the way or all the way up from the down position even if the limiter switch was inoperable for any reason.

Correct, The set height of the recommended 21 3/4 inches from pin to pin would constantly move out of adjustment if the screws are missing on items 6 - 9,
http://www.mercruiserparts.com/Show_...STEERING+LEVER

The 21 3/4 inch limiter adjustment from pin to pin set is set between item numbers 13 & 20 while going/holding the trim up button,
http://www.mercruiserparts.com/Show_...YDRAULIC+HOSES

Yes I agree, you have a lot more diagnostic work ahead of you.

You may be surprised, Sometimes that's not always the case. With something basic like the trim system, does not necessarily mean you need to take the boat to the highest dollar marine shop in town with high overhead.

My pleasure.

I just wanted to point out that this is exactly what I was talking about, I would love to hear if you have any other ideas for what could cause this. Essentially the port trim switch (on the throttle) is acting exactly like I'm pressing the port trailer switch, the starboard drive twim/trailer switches act exactly as you would expect (at least in this case, lol). My first hunch was of course that someone jumpered it together to make a workable hack, but I know that this could have been done anywhere from the controls all the way back to the drives, and might be hard to locate, it's a big boat and has lots of wires...

I have an idea for testing this theory but I wanted to make sure I wasn't overlooking anything, I'm certainly no electrician and this is my first boat, but I'm usually really handy. Can you confirm the following: when the drive is within the normal range of the trim switch (let's say full down), the resistance between the purple/white and blue/white should be ~0ohm, but when the drive is raised beyond the normal limit of the trim switch (such as full up), the resistance should be infinite? I'm basing this theory purely off of my own (limited) understanding of logic circuits, so don't ask where I got such a crazy idea if it is such :-)

Depending on the way the trim system wired up, I could foresee it as one of four things possibly wrong.

One would be someone jumped the limit wire together like mentioned above. (On the inside of the boat along the transom area there should be a purple & white wire and a blue & white wire in close proximity of each other. They go to the trim limit switch. if they are joined together with a jumper wire then that would explain the trim switch going all the way up like the trailer switch. There should be two black wires plugged into them coming from the limit switch.)

Two would be the limit switch just needs to be readjusted back to within normal limiting range. If it's out of range, then the limiter would not know when to stop and just keep on going.

Three could be a bad limiter switch.

Four would be if you happen to have a Dual Power Trim Terminal Block Module System, then you may have a bad electronic component inside the module box. If you do have this system, it's testable using this section of the manual.
http://www.boatfix.com/merc/Servmanl/11/11c5r5x.pdf

To find if the limiting wiring is jumped, It would most likely be at the back of the boat by purple & white, blue & white wires.

Off hand, I don't recall the usual ohm numbers as that is usually not done to set this system up. On the back of the sending units, there is an index mark to align up for a starting point, then you fine tune the adjustments as needed.

Also you would not be ohms testing the purple/white and blue/white wires, you would be testing the two black wires that plug into them coming from the outside of the boat. There are two set's of wires with a total of four wires on one engine package. The wires coming in on the port side is the trim limit wires that should plug into the purple/white and blue/white wires.

The best advice I can give you is, since you know one side works normal for the trim limit, study how that one is wired, etc, etc, then see what looks out of place on the other side including an ohms test if desired while raising and lowering the drive.

See pages 4A-9 - 16 for trim switch installation,
http://www.boatfix.com/merc/Servmanl/11/11a4r5x.pdf