Help Needed!!! Outdrive Problem

[cherokeeguy]

I am not new to boating but i just purchased a different boat it is a 84 270 with a 330,velvet drive and MercTRans II out dive seeing as how the boating season is here and the dealer that i bought it from would take untill july to actully fix the problem (took 2 months to replace a alternator) I have taken the boat and they are supply the parts to fix what it needs, NOW THE PROBLEM, basicly the outdive trim works up and down and for trailer there are no hydrolic leaks that i can find but when you are under way in the boat the outdrive will not maintian anything in the up possition, you can trim the drive up and then when you release the button you can watch and feel the outdrive lower back down all the way, also when sitting still (docked) it seems like it will hold in the up possition but after a few days it say sank considerably I am not sure were i should be looking for this problem so any help would be greatly appreciated. Thanks

 

[sdrevik]

Just brainstorming here:

when you release the switch, does it go back down slowly or quickly?

the fact that it goes down quickly while underway but slowly (if at all) at dock makes me wonder about the switch. The fact that it moves at all with the ignition off makes me wonder, though.

One possible test- dock it, put the outdrive all the way up, and disconnect the battery. If it still goes down it has to be some kind of hydraulic leak or mechanical problem. If it stays put, it's electrical. (right??)

 

[Bobby LaChance]

It sounds like a check valve on the pump. When the boat is underway there is a lot more pressure put on the hyd. system.

 

[NateRW21]

I doubt it's anything to do with the electrical aspect of the system; I'd guess some sort of check valve/seal as well. Somewhere there is hydraulic pressure escaping.

 

[fc3]

Check the oil level and that there is no air in the system. There is a valve on the pump that allows you to manually lower the drive. Check that the valve is closed. There's an O ring on the manual valve that could cause the problem. It's a cheap fix.

After that the problem is either in the pump or the cylinders. The cylinders are easy and inexpensive to rebuild. The pump is expensive.

 

[boltman]

I agree with FC3 this is a pressure problem, somewhere theres Fliud be forced back into the tank from the pressure of being underway. Start with the Check valve if there's no visable leaking from the cylinders.

 

[cherokeeguy]

Just wanted to say thanks for all the replys, I was able to pull the boat monday and got a chance to look at the system last night there are no visable leaks of any kind and it does hold fine when not under pressure what i was told is that the pressure created by the 20" prop under way is causeing the check valve to release pressure so I am going to replace the springs tonight and from all the i can see that should solve the issue. Thanks again