Mariner 1991 75HP tilt/trim drifting down

[marty53]

Hi folks, haven't been around in a while since my motor has been running sweet for almost 2 years, and still is. My issue now is with my tilt/trim system. When my rig is sitting in my driveway, the motor slowly drops after about a week until the skeg is resting on my driveway. Also when I raise it back up the motor sounds a little bit like its dying for the first few seconds then starts working properly. I am working with a newly charged battery so I have eliminated that as a possibility. Motor has only ever been in fresh water. It is the 2 ram system I believe, pic attached.



I know there are two relays I can replace, would they cause this or am I looking at a new motor or a rebuild, or maybe just low fluid? Can someone give me a checklist to go through?

Thanks for any help provided.

 

[fisherman81654]

Re: Mariner 1991 75HP tilt/trim drifting down

Hi folks, haven't been around in a while since my motor has been running sweet for almost 2 years, and still is. My issue now is with my tilt/trim system. When my rig is sitting in my driveway, the motor slowly drops after about a week until the skeg is resting on my driveway. Also when I raise it back up the motor sounds a little bit like its dying for the first few seconds then starts working properly. I am working with a newly charged battery so I have eliminated that as a possibility. Motor has only ever been in fresh water.

I know there are two relays I can replace, would they cause this or am I looking at a new motor or a rebuild, or maybe just low fluid? Can someone give me a checklist to go through?

Thanks for any help provided.

It sounds like to me the motor is bad,maybe the brushs inside or could have water in it.Its not likely that both realys went bad,check all connections make sure that they are clean and tight.
Also it seems that you have a seal or Oring leaking,that could be in a lot of places,but my guess is that you have a Oing leaking around the pump which would also affect your motor.
Make sure your fluid level is full,if its not it,its going somewhere.

You have a three ram system ,same as mine.

 

[Texasmark]

Re: Mariner 1991 75HP tilt/trim drifting down

That is a long time to have engine stay up, but still it is falling and fluid is apparently either sliding by the piston seals, or one of your up-down valves is leaking would be my answer. The noise you hear may be due to low fluid in the reservoir. On mine you tilt all the way up and remove the plastic screw (about the size of a quarter) on the side of the reservoir...can't miss it, and full is fluid even with the bottom of the threads....more and it would overflow with the plug out. Merc makes a PTT fluid for those units.

Mark

 

[marty53]

Re: Mariner 1991 75HP tilt/trim drifting down

Thanks Mark. I guess making sure its filled with fluid would be an easy first step.

Sounds like both of you are in agreement that I have a bad seal somewhere, how do I go about replacing the seals?

 

[fisherman81654]

Re: Mariner 1991 75HP tilt/trim drifting down

Thanks Mark. I guess making sure its filled with fluid would be an easy first step.

Sounds like both of you are in agreement that I have a bad seal somewhere, how do I go about replacing the seals?

Do a search on trim/tilt on this site,look at some of my posts also.
here is a site to order parts for the trim/tilt unit http://www.crowleymarine.com/mercury-outboard/parts/553_240.cfm
But it seems to me you have not check the fluid lever yet.
Start there,also you have a manual relase valve on starboard side of tim/tilt unit,about the mid section,there will be a round flathead hard plastic screw,recessed back in the transom bracket.
Turn it clockwise and make sure it is tight,dont strip it out.
Take pictures before you start a rebuild and as you go read and read posts on this forum.
If you have a manual for your motor ,that will also help you a lot.

 

[RRitt]

Re: Mariner 1991 75HP tilt/trim drifting down

seals are made of rubber. they get old and start to harden. as time goes by the drift down will get faster and faster until it is difficult to put the boat on a trailer. It doesn't really harm anything to wait.

Trim motors last forever or until water gets inside - whichever comes first. If the motor is just starting to hint at problems then look for where water may be getting in. Based on age of your system a cracked cable jacket is the usual suspect. Let it dry out really good and paint seams with rubberized paint. They aren't worth fixing. The parts cost more than an aftermarket replacement. Made in US aftermarkets are just as good as original and imported are within acceptable quality for price. If aftermarket then through bolts are probably not stainless - so paint them.

you should be blocking your engine up for towing and storage. when the drift down gets bad enough to fix then you have a range of options costing from 250 - $1000.

 

[marty53]

Re: Mariner 1991 75HP tilt/trim drifting down

Wanted to post an update to this. I finally got around to addressing my slow drift down on my Mariner 75 which had gotten worse since I started this thread. There aren't too many threads on this issue that I've found so I'm sure it will help some folks.

I have the motor on a new boat now, a 2004 Sylvan S170 I got for a song with a blown johnson (no pun). I checked the fluid, and it was low (couldn't see it in fill tube with engine tilted fully up). I decided I would completely flush the system. So here is what I did:

I tightened the fill screw back up, then dropped the engine back down and unscrewed the manual release valve and drained all the fluid. The manual release valve itself looked fine to me (i'd heard these can cause slow drift down). The fluid was red and quite clear, not milky at all so didn't look like water was getting in.

With the motor down, and the manual release valve open, I pulled up the motor (wow its heavy) and propped it up with some metal bars. Then I closed the manual valve release valve, and opened the fill valve and filled it. Dropped it down with the power tilt, brought it back up and down a few times for the automatic bleed, then fully up, then topped it off a final time. Anyway, that was at about 3pm yesterday. I left it about 3/4 up then, and this morning at 7:30am the motor was exactly where I left it!

I have the factory manual, but it was a little unclear on exactly how to do this process. Hope this helps someone. I was hoping I wouldn't have to replace the whole unit. Looks like I'll get some more years out of it!

Thanks
Marty