I have a 1986 Mariner 50 hp outboard with what appears to be the original tilt/trim unit. It is a single black reservoir/motor assembly with 4 hydraulic hoses, two hoses going to each hydraulic ram mounted behind the transom on the motor. This is my first boat. The first couple times operating it, I noticed that the motor would slowly fall down to low trim while running, it would trim back up fine, but eventually would go back down. The rate of decent is variable, in fact sometimes, I think it does hold trimmed up for an extended period, other times, it will take 1 minute to fall down under power. If I have the motor tilted clear up on the trailer, it will slowly fall down over the course of an hour or so. Here is what I have done:
I made sure the reverse lock was engaged (turned clear out), which it was.
The pump does not make any abnormal sounds while operating so I don't think I have air in the system.
I can't detect any visual external leaks so I don't think I am losing fluid.
I added recommended fluid (clean 10W40 motor oil) so it reaches the bottom of the fill screw with the motor tilted clear up. It took a decent amount of fluid to fill it to the proper level.
It still behaved the same after filling.
I have fiddled around with the reverse valve...disengaged and moved the motor up and down manually from full down position...no luck.
I called a reputable marine repair shop and over the phone they informed me that the manifold is probably shot, which is a $700 part + labor and while I will not be surprised if this is the issue, I want to exhaust all other options before I spend that kind of money.
I have read on the forums and some people suggest removing the reverse lock and checking the o-rings and making sure it is clean. Will I lose all my fluid if I do that? It looks like I would unscrew a nut that is holding on the reverse lock valve.
I have read that it is usually not necessary to drain and refill the fluid unless it is contaminated. I don't know if it is contaminated since I bought it used. I have the clymer service manual (general manual for a bunch of Mariners including mine) and it discusses how to fill and how to bleed the system, but provides no information on draining the system. Should I do a drain and refill to make there there isn't any gunk in the reservoir?
Is there anything else I should try before dropping mad cash for a new unit? I am pretty handy with tools, I just have never torn into a tilt/trim unit before. Is there any reason to believe that bleeding the system could help form what I have described?
Until I get this fixed, I am going to install my tilt pin higher so that it is not always falling to full down trim, but eventually I want to get this fixed. Any advice at all is appreciated.
I made sure the reverse lock was engaged (turned clear out), which it was.
The pump does not make any abnormal sounds while operating so I don't think I have air in the system.
I can't detect any visual external leaks so I don't think I am losing fluid.
I added recommended fluid (clean 10W40 motor oil) so it reaches the bottom of the fill screw with the motor tilted clear up. It took a decent amount of fluid to fill it to the proper level.
It still behaved the same after filling.
I have fiddled around with the reverse valve...disengaged and moved the motor up and down manually from full down position...no luck.
I called a reputable marine repair shop and over the phone they informed me that the manifold is probably shot, which is a $700 part + labor and while I will not be surprised if this is the issue, I want to exhaust all other options before I spend that kind of money.
I have read on the forums and some people suggest removing the reverse lock and checking the o-rings and making sure it is clean. Will I lose all my fluid if I do that? It looks like I would unscrew a nut that is holding on the reverse lock valve.
I have read that it is usually not necessary to drain and refill the fluid unless it is contaminated. I don't know if it is contaminated since I bought it used. I have the clymer service manual (general manual for a bunch of Mariners including mine) and it discusses how to fill and how to bleed the system, but provides no information on draining the system. Should I do a drain and refill to make there there isn't any gunk in the reservoir?
Is there anything else I should try before dropping mad cash for a new unit? I am pretty handy with tools, I just have never torn into a tilt/trim unit before. Is there any reason to believe that bleeding the system could help form what I have described?
Until I get this fixed, I am going to install my tilt pin higher so that it is not always falling to full down trim, but eventually I want to get this fixed. Any advice at all is appreciated.