Issues with MC1 trim - burned up two trim pumps in one weekend - help

demian5

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Jun 17, 2020
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6
Help -

I have a 1979 Glastron Carson CVX16SS with a mercruiser 140 (3.0). I have been through most of the boat. New engine and components, serviced the outdrive, even had the transom off to replace gimbal ring and pin and reseal. Replaced the shift cable as well. As with most restos, more work than you can list. I replaced the trim limit and position switches and adjusted the limit switch per specs.

I'm going to tell everything I did whether it was right or not, to see if someone can ID the issue.

The trim worked fine for 41 years. I topped off the fluid last season with mercury trim fluid, and it worked even better. I did notice a slight seeping from the reverse lockout valve attached to the transom mount, but very slight so figured that's where my fluid was going. Again, not an issue. Had to replace the glass fuse near the 3 button switch with a blade in a waterproof housing since it blew on the ramp one day in 110 degree heat. Again, worked fine.

Took it out a few weeks ago and it was working great. We went into a narrow area and I saw what looked like trash floating on the water, figured Id be a good boater, slow down to idle and snap it up as I went by.

Well, it was a home made marker, the rear of the boat lifted up as the skeg hit the rock. Again I was idling. I raised the drive and we got out and inspected it, seemed OK, a little grindage on the skeg, its a 16' boat so not a ton of weight and again, was idling no wake to pick up the "trash" so we kept going, monitoring the bilge and making sure we weren't taking on water. Towards the middle of the day, the trim stopped working, no up or down, only the sounds of solenoids clicking.
My wife told me she noticed when going into reverse that the outdrive lifted up and she had never seen that before at all.
We stayed out for the remainder of the day and enjoyed the water (lower Colorado). Got back to the ramp, put the boat on the trailer and I was able to manually lift the drive by hand to trailering position.

I looked for a pump since jumping the pump and everything else I tested, lead to the pump being bad. I was getting voltage and power to the right places at the right time. I was lucky to find a used good pump from Yuma Marine. I got there in the AM and swapped out out in the parking lot. We tested it before I took possession. Went to bleed after filling with the right motor oil from the shop (drive still in trailering position) it would move a hair down and that was it, replacement trim pump didn't work anymore and jumping it didn't do anything either. Solenoids clicked, jumping trim limit switch made no difference.

Im at a loss.

I got another used pump and motor and a complete harness from a guy who parts boats in MN. I also got the block that attaches to the pump, as the one on my boat had crack in the fitting. Also, the trim pump oil is all over the bilge in my boat now...

After looking around, I'm almost thinking something is an issue with the reverse lockout valve (drive raising in reverse). Any ideas? Suggestions? I know nothing about the reverse lockout valve or how a strike could cause this. I can diagnose with the right diagrams.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
You're using second hand pumps, so the amount of life left in them is 'unknown'. You'd need to pull the pump motors apart to find out why they stopped working (and that's what I'd do). I would suspect the brushes have reached 'end of life'...

You also say you have oil in the boat now (I assume you mean trim oil). Likely when you hit the rock, the act of the drive kicking up (as designed) has ruptured an already weak seal in the reverse lock valve...

I will scan in the hydraulic flow diagram for the kick up circuit in the next post.

Chris.........
(I have also deleted your post in a 3 year old thread. Please don't add to old threads unless you are the original poster. Please read the forum rules regarding old threads.)
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Here's the relevant pages from the Service Technician's Handbook....

trim.jpg
 

demian5

Cadet
Joined
Jun 17, 2020
Messages
6
So the trim cylinders are designed for this and will reset? That's what I'm reading... I believe at my speed it qualifies as "Strike object with light steady pressure.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Then you have a problem. You have a reverse lock valve in the system, and it does exactly that, locks in reverse. Nowhere for the fluid to go, something with break, or a seal will blow.

Chris...
 

demian5

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Joined
Jun 17, 2020
Messages
6
So.... How could I burn up one pump, then install another and burn it up too? Doesn't the pump have internal bypass for overpressure? I'm at a total loss. What could do this?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
As I said, you're using second hand pumps. Pull one apart and see WHY it died. It might just be brushes.

Chris......
 

demian5

Cadet
Joined
Jun 17, 2020
Messages
6
I got it sorted out with another pump and then converted over to dual solenoids. I guess my pumps were just bad and it was coincidence. I tested the switch numerous times and it worked great and consistent. My reverse lockout on the hydraulic line was never adjusted right. It is now, maybe thats why my outdrive kicked up whenever I went backwards...
 
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