Thanks all. This site is great. You all have interesting points. If I only had some daylight to disconnect the rams to check whether the rams are binding or move at different rates. If I had an internal leak, you'd think the drives would readily drop from just the weight of the drive. The problem drive stays up no matter what and only drops if I hold the down trim switch for 3-5 minutes. The sound I hear is a laboring pump, not the high pitched whine of air in the system. This is why I think internal valving in the pump is not working. If there was a stuck ram, would it not also affect "up" which works fine?

Does anyone know anything about the "down relief valve" that is supposed to be in the pump somewhere? I've seen part offered for sale, but no pictures or diagrams. I've never seen anything as hard to come by on the internet as the hydraulic diagrams for these trim systems. I'm hesitant to start taking the pump apart without a diagram telling me what's where. I've got a merc manual coming next week that I bought on ebay, but would like to get this problem solved by this weekend.

You can buy the complete pump assembly from Offshore Performance Specialties for about $350.00. If you can swap the lines at the pump and see if the problem goes from down to up. remember if you do this the switches will be reversed.

The relief valves just screw into the bottom side of the pump housing. Drop the plastic resorvior by removing the single screw on the bottom side.

I also would try swapping the lines and see if the problem follows.

I have the same problem with my 2015 Bravo III drives. I switched the lines at the rear of the transom and the drive does down perfectly. It then will not go back up. Switch the lines back to normal position, And it goes up perfectly but not down. I would think this indicates a pump issue. I loosened the 7/8" nut on the right side of the pump (down side of the pump) while activating the pump in the down position (drive is in the up position). Fluid leaks out as it should. I thought the shuttle valve might be stuck. This did not help the problem. My unit is newer and has the quick connects on the two lines going to the drives. They have never been touched. My next step is to pull the pump. Any input is appreciated and maybe can solve everyone's issue with the same problem.

Mine had this issue, well both of my Bravo 1s (they all use the same rams/pumps). Anyway, replacing all the rams fixed mine. The 'up' part of the pump has more power than 'down'. (has to fight the thrust from the prop) so I was able to swap the lines to the the drive down for summer, and use the engine prop thrust to get the drives to go down when needed (only a month of summer left). (some people have a friend jump up/down on the drive as they push down button).

That winter I put new SEI Rams on both drives (now 4 years ago) and been fine ever since.

https://www.sterndrive.cc/product/Fi...-98703A26.html

I did all new lines as well. Much cheaper than OEM and worked fine for me.

I'm trying to remember why I did the rams and not the pumps, but maybe it was because they (rams) were corroded to hell anyway.

Probably a bad solenoid. The down one uses a green wire.

The pump runs and sounds normal in both up and down directions. I may purchase a hydraulic meter and test the lines at the drives. If they test out, I would then agree the rams are the problem. If not, the problem is in the pump. The drives have never sat in the water for their entire life (lift kept) and flushed every time used. I have no corosion on the drives and the anodes are original and in great shape. If a solinoid were bad, I would think you would not hear a normal motor load. Either a click (not making proper contact) or nothing. There is very little if any difference between the sound of the pump going up or down, even though the drive is moving up and not down (in). I feel it is a hydraulic problem, not electric.
I appreciateyour feedback.

Formula 370 SS

You say the drive goes down very slow. How does it do when going up?

The drive does not go down slowly. It does not move in the down position when activated. It goes up perfectly normal when activated. Wirh a 225 lb. Person jumping on the drive while the switch is activated will cause the drive to move down in short movements. It will also go down while under thrust while in the water. I will be checking presure at the rams with a meter provided I can find one.

370SS Formula

Any growth or barnacles by the rams? not that it should affect it but it’s strange, is your pump working correctly, is the fluid a strange color?