1975 Mercruiser Tilt/trim issue

K

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,527
Look up a post from May 11 this year. The poster replaced his old style Prestolite pump with a newer style “Oildyne” style. I explained how to adapt the style with pipe fittings from the local hardware or auto store.
The only parts available for your pump are some of the electrical and none of the hydraulic unless you take a shot on used stuff.
As Bondo explained replacing the hoses is easy as he described. However if your hoses are good leave them alone.
 
R

rogerrabbitis

Petty Officer 3rd Class
Joined
May 25, 2003
Messages
86
Bondo said:
Nope, there should be 2, 7/16th nuts at the bottom of the transom that hold the manifold in-place, removing 'em allows pulling the manifold down, to unscrew the inside lines,....
Click to expand...
oh ok I did not know that I will have to take a look thanks for letting me know this
 
R

rogerrabbitis

Petty Officer 3rd Class
Joined
May 25, 2003
Messages
86
kenny nunez said:
Look up a post from May 11 this year. The poster replaced his old style Prestolite pump with a newer style “Oildyne” style. I explained how to adapt the style with pipe fittings from the local hardware or auto store.
The only parts available for your pump are some of the electrical and none of the hydraulic unless you take a shot on used stuff.
As Bondo explained replacing the hoses is easy as he described. However if your hoses are good leave them alone.
Click to expand...
ok thanks I will look up that post and from my test I don't belelve I have a collapes line when we crack the line at the pump the pressure gets realsed and drive goes down witch I belelve it tells me it's with the valve in the pump sticking when high pressure
 
R

rogerrabbitis

Petty Officer 3rd Class
Joined
May 25, 2003
Messages
86
I am going to try to use it this weekend and see how it goes... oping it may clear it's self at this point till I find a new pump
 
R

rogerrabbitis

Petty Officer 3rd Class
Joined
May 25, 2003
Messages
86
HI all so I used the boat over the weekend did not really rase it all the way to the top and it worked ok I noticed though when putting in reverse the lower end went up on it's own all the way is that a ram issue or ? also my trim indicator is always showing up also I have one of these any idea what it does ? 1781017018030.png
 
Bondo

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,457
also I have one of these any idea what it does ?
Click to expand...
Ayuh,..... That, is the reverse-lock, 'n the trim indicator,.....
 
Scott06

Scott06

Admiral
Joined
Apr 20, 2014
Messages
7,458
rogerrabbitis said:
it does both ?
Click to expand...
yes. Get a factory manual for your set up you will find it invaluable

if drive came up in reverse I would think you have a bad reverse lock out. After the R drive (and later MR/Alphas) replaced the set up you have in 1982 or so this was all done differently not sure if lock out was done in the pump, Kenny or Bondo likely know
 
Bondo

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,457
Scott06 said:
yes. Get a factory manual for your set up you will find it invaluable

if drive came up in reverse I would think you have a bad reverse lock out. After the R drive (and later MR/Alphas) replaced the set up you have in 1982 or so this was all done differently not sure if lock out was done in the pump, Kenny or Bondo likely know
Click to expand...
Ayuh,...... Reverse lock is done in the pump on later systems,.....
Drive position is done in the pucks, after they were added to later drives,....
 
K

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,527
The trim limit switch on your boat was designed to last about 13 months [ one month out of warranty] that is why you need to press both buttons to raise/trim your drive. The hydraulic trim sender is seperate from the reverse lock valve which is incorporated with the shift linkage. Try to post a picture of the shift linkage that shows the reverse lock valve.
 
R

rogerrabbitis

Petty Officer 3rd Class
Joined
May 25, 2003
Messages
86
here is a picture i'll have to try to get a better one when I go back to the cottage to the boat I am thinking my leak is coming from the reverse lock valve I have ordered a leak detection dye to hopefully help find the leak would it be an idea to bypass with limit switch ? 1781227644482.png
 
R

rogerrabbitis

Petty Officer 3rd Class
Joined
May 25, 2003
Messages
86
here are some better pictuers but I think I found it's leaking from the reverse lock out there seems to be two O-rings that maybe bad I am going to see about replacing but was told most people just by pass it anyone done that what do I need ? 1782135851971.png1782135916983.png
 
Bondo

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,457
Ayuh,..... If yer still running the original trim pump, you need the reverse lock,.....
Otherwise, anymore than idle in reverse the drive jumps up high,......

I switched to a newer plastic tanked pump, which has a built-in reverse lock,....
 
R

rogerrabbitis

Petty Officer 3rd Class
Joined
May 25, 2003
Messages
86
Bondo said:
Ayuh,..... If yer still running the original trim pump, you need the reverse lock,.....
Otherwise, anymore than idle in reverse the drive jumps up high,......

I switched to a newer plastic tanked pump, which has a built-in reverse lock,....
Click to expand...
ya I am trying to find a possible replacement pump as of now in reverse the out drive will jump up :(
 
K

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,527
There are many tiny ball bearings in the valve. They get lost easy so be careful. If you take it apart and replace the “O” rings do not be surprised if it still leaks. If you do R&R the valve make sure that the pump does NOT operate when the drive is shifted to reverse. Good luck.
Start looking for a later style pump like Bondo has done and record the instructions I gave in my May 11 post.
 
Last edited:
You must log in or register to reply here.
Top