Boat burned up 2 trim pumps in one weekend - help

[demian5]

All - On my 1979 CVX 16 SS with 140 mercruiser (and original trim system with 3 button controls), I burned up the original pump after 41 years. Original single solenoid pump, all wiring looks good and nothing looked messed up at all. I didn't think that there was any issues just an old pump that had its day. Since I was in AZ for the weekend, I looked for a pump and found a good used one at a local boat repair shop. I installed it, put fluid in it, it worked up and down for a minute, then stopped working. Burned out another pump. Aftr a morning in the hot AZ sun in a parking lot swapping it out

Reason why I say burned up, is that even jumping directly to battery power and ground, the pump doesn't run.

I have another good used low hour pump coming, AND I have a dual solenoid setup I plan on installing (I have the bracket and everything for it). I also have another control switch and harness coming that was working with the pump that is coming.

My questions are:
- Does anyone have any idea why my boat would burn out the pumps?
- How can I wire up a circuit breaker or something to protect the pump from here on out?

Thank in advance.

We did have a great time, the new motor and prop got me up to about 40 MPH at 4300 RPM. I was able to manually raise the drive to put the hook on for transport as well. AND that pool at the hotel was amazing after the time in the sun with the second pump.

[Plugcheck]

Take a look at the voltage at the drive motor when running.   Likely the solenoid contacts are marginal and not allowing sufficient voltage to feed the pump motor.  Most trim pumps have 20a thermal breakers on the motor drive line, and agc fuses on the solenoid coil lines.   

[demian5]

But who would it literally ruin the trim pump motors? They don't even work when jumping directly to a battery.

[Plugcheck]

Possible debris in tank locking up pump?  If jumping battery directly to motor doesn't get it to turn then that's one possibility.  Never seen this same condition before, all the trim pump failures I've seen have been inability to make or hold pressure. 

[demian5]

Possible debris in tank locking up pump?  If jumping battery directly to motor doesn't get it to turn then that's one possibility.  Never seen this same condition before, all the trim pump failures I've seen have been inability to make or hold pressure.

Well, I swapped the tanks when I swapped the motors, BUT I did transfer over the reverse lockout block on the bottom.

Hmmm.... When I swap this time, Ill lower the rams to see of they move freely and move fluid, and the pump Im getting has a different block. But thats a good thing to look at.

What does the block do when combined with the lockout at the top?

[thedeuceman]

odd that it would burn up 2 motors, would be interesting to open one up and see if its baked.
maybe just "dumb luck" that the used replacement went bad ?
adding a thermal breaker would save it if it were an overload problem, also if that's the case you should hear the pump "laboring" when running the trim on the trailer.
im sure i have see a schematic somewhere but i cant seem to find it right now, as i recall the block on the bottom of the pump has the valve that directs the fluid for up/down, the lockout that on the snifter cable prevents the drive from going up when in reverse.
i think the newer stile pumps don't need the lockout.

[Plugcheck]

The reverse lockout is important to have functional, as Joe said, the drive will kick up in reverse since the block permits flow that direction.  If memory serves, it blocks the font segment return.    One other caveat to trim pumps, many have different pressure values(limits).  Trim up I believe is around 2500-3000psi, but down is somewhere around 1500.  As Joe stated, I'd be curious to know what the electric motors look like inside, or if they run when disconnected from pump.   

[demian5]

The reverse lockout is important to have functional, as Joe said, the drive will kick up in reverse since the block permits flow that direction.  If memory serves, it blocks the font segment return.    One other caveat to trim pumps, many have different pressure values(limits).  Trim up I believe is around 2500-3000psi, but down is somewhere around 1500.  As Joe stated, I'd be curious to know what the electric motors look like inside, or if they run when disconnected from pump.

When the drive was stuck in the down position (1st pump already gone), she did mention when putting in reverse, the outdrive moved quite a bit when moving in reverse. I wonder if fluid flow through the block and the thing at the shift cable could cause this? I don't know. All I know is I don't want to burn up another one...


Also, what would cause the the system to send power to both sides of the pump at the same time? And would a double solenoid setup (opposed to the single I have now) possible prevent this from happening again?

And if im correct, I should not have been able to lift the outdrive up when it was on the ramp after the pump failed? Could it be a reverse valve issue?

[demian5]

Can damaged trim cylinder check valves cause this issue?

I hit a rock and then they stopped working. Is it the reverse valve?

[thedeuceman]

Can damaged trim cylinder check valves cause this issue?

I hit a rock and then they stopped working. Is it the reverse valve?

I don’t think that would cause the pump to burn out that fast.
In your last post you made a comment about both wires getting power at the same time, are you talking about the blue and the green? I believe that would cause the motor to burn up. You may have a stuck solenoid or a bad switch that’s stuck on ?
On the single solenoid unit the down is wired directly to the switch in the app is wired through the solenoid because it takes more current when you’re under power, apparently at some point they thought it would be a good idea to have 2 solenoids so the switches didn’t get beat up quite so bad. I would verify the wiring with the meter or test light before connecting the new motor.


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[demian5]

If course I'm going to check out the electrical. I'm thinking that hitting the submerged rock at idle speed may have something to do with thi. It worked fine until after that. The drive would lift a lot when in reverse.

[demian5]

So I tested my switch operation and it was fine. Solid, nothing wonky. I installed the replacement pump with 2 solenoids and found that the reverse valve a was never adjusted properly (it always seem to kick up in reverse). Got it all on, had the drive all the way down and added 30w motor oil. Left the vent open, then ran it up and down a few times and its all good! So maybe both pumps I had were ready to go... I don't know. This one is pretty strong sounding when it runs, and it goes up and down solid.

Now, who can tell me how to adjust the shift cable since I mat have taken it out of adjustment when messing with all of this.

Thanks again.