78 i/o mercruiser trim will not lower

[johnnyg2003]

started getting boat ready for summer. first 5 or 6 times trim worked fine. tried to lower but it wouldnt go down. pump motor is working. kinda makes a little higher pitched noise when i try to lower. took pin out of hyd cylinders, didnt help (can raise and lower outdrive by hand). took pump off and put it back on. it worked 5 or 6 times and then wouldnt lower again. could this be a air problem (need bleeding) and if so how do i do it? any help is greatly appreciated.

 

[Trent]

Re: 78 i/o mercruiser trim will not lower

System is self bleeding.<br /><br />You probably have the prestolite pump but things work the same.<br /><br /> Troubleshooting

 

[johnnyg2003]

Re: 78 i/o mercruiser trim will not lower

took pump completely apart. everything looked clean. didnt see any foreign material as suggested. any thoughts on this? thanks again for the help.

 

[kdmiller8251]

Re: 78 i/o mercruiser trim will not lower

Try flushing the system, My pump was having same problems. I flushed the system and it seems to work ok now...<br /><br />Disconnect the lines at the cylinder 2 at a time, the up ones at same time then the down ones..<br /><br />While they are disconnected run the pump so it pushes the fluid out.....<br /><br />Tallman

 

[Snailman]

Re: 78 i/o mercruiser trim will not lower

Can you compress the hydrolic cylinders by hand? You should be able to disconnect the braided lines from the cylinders and compress them by hand. Hydrolic fluid will shoot out so watch out. If you can't then your cylinders probably need to be replaced. There is a rebuild kit for them if they're not too far gone. Mine were too far gone.

 

[johnnyg2003]

Re: 78 i/o mercruiser trim will not lower

took pump apart again. this time i soaked valve body and other internal parts in cleaner and put new o-rings in. it seems to be working now as long as i dont raise ourdrive all the way up. it still hangs up then,but if i stop raising an inch or so from full extension of cylinders it works. to answer earlier question, with lines off cylinders can be pushed and pulled by hand. thanks again guys