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New guy, big tilt/trim problem-1986 mariner 90 hp i-6, tilt goes up and down, but will not hold.

N

njrextreme

New member
I have a problem where the tilt works up and down, but when in the water under power the motor gets pushed down. I was told it is the top seal in the main hydraulic cylinder. So I pulled it apart and the o rings look good. Can anyone give me some help on what it could be and how I should go about checking and fixing this thing. I cant afford to buy a 800 plus dollar unit for this old boat. Thanks for any help. Im also on I boats and not getting any help.

Here is a pic of the internals of the main cylinder.

My name is Nick, I live in Illinois, And I have a 87 ebbtide dyna-trak 156 ss with a 74 merk 115 tower I-6 on a 86 Mariner lower leg. I did the swap myself after the the Mariner 90 blew up.

Nick R.
 

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Seeings how you have the cylinders apart you might as well rebuild them. Just because they look ok doesn't mean they are. Depending whether you have a 3/4" or 1" there will be 9-10 o-rings to replace. Did you make sure the system was full or if it had any air in it prior to dis-assembly?
 
I only have the main cylinder apart not the two smaller lower ones. Yes, I did bleed the system last season and it still would not hold the motor up under a load. If I push down on the motor I can hear air leaking out, like a squeel sound,but wasnt seeing any fluid anywhere. I do remmber seeing that the ram did have oil on chrome shaft part last year when out in the water. Are you saying I should replace all the o rings on all 3 cylinders?
 
The resi was full and there was alot of atf when I removed the top cap on the ram cylinder. It looked clean also. Im not sure if it was completly full or if I even bleed the system corectly. Im new to this hydraulic stuff. What I think may have been the right way, may not of been. All I know is the fluid was full, and the motor stays up by itself until I put it in gear and then it drops all the down and the front of the boat is riding in the water.
 
Sorry bout that on the old style. If you are seeing oil on the ram itself then atleast replace those they do shrink up over time some more than others. If you have the system out l would rebuild it as o-rings are cheap. You bleed the system buy cycling it up and down a few times then all the way up and check the level and fill to the full mark then cycle once and check level again. Also check to make sure the manual relief valve is tight and not leaking.
 
Your tilt is to tilt the engine up and down,your trim is to help you plain out your boat!!when you lower your tilt you should have two more little trim tabs that trim it.youshould have a pin that the engine rests against and your engine should not go down when rested against that pin..
 
Yes, I do have that type of system. There is a pin/bolt that holds the motor when down. But should the main tilt ram hold in place when under a load? Im almost sure it did before. Now it just gets pushed down and the boat is not triming with the switch. It just rides nose down in the water.
 
there is alot of pressure when it is not on the pinn,yes it will move.Not only that having your engine that far up makes the front of boat rare up because prop is forcing back of boat down.Thats what the pinn is for.the big cylinder is just a tilt to transport boat so you dont have to pick it up yourself.Thats what i was taught about that years ago from dealer!!
 
A few of those replies sound a little unclear... So, ill try to make it clearer...
That tilt ram should hold the motor up. It does have valves in it, to allow it to drop when under heavy load, that is about 50% throttle.
When the tilt ram drops, it should only drop to the trim rams. From this point to all the way down is referred to as the trim range..
The trim rams should hold the motor in any position, any throttle setting whist in the trim range.
You problem will be either trim piston O-rings, manual release valve O-rings, or hydraulic pump Orings or even issues in the pump unit itself.

If you have the hydraulic unit out, you should replace all seals/o-rings in all the rams and the motor/hydraulic pump, and also the manual release valve.
This almost always sorts out any creeping issues, if it doesnt, you ll then need to replace the hydraulic pump, but all is not lost as you ll also have fresh seals/O rings in the unit...
 
Thats what i was trying to say,and it came out different i guess!! Tonyaus made clearer.Like tonyaus said you have it out might as well replace everything.Sorry for any confusion!!
 
tonyaus said:
A few of those replies sound a little unclear... So, ill try to make it clearer...
That tilt ram should hold the motor up. It does have valves in it, to allow it to drop when under heavy load, that is about 50% throttle.
When the tilt ram drops, it should only drop to the trim rams. From this point to all the way down is referred to as the trim range..
The trim rams should hold the motor in any position, any throttle setting whist in the trim range.
You problem will be either trim piston O-rings, manual release valve O-rings, or hydraulic pump Orings or even issues in the pump unit itself.

If you have the hydraulic unit out, you should replace all seals/o-rings in all the rams and the motor/hydraulic pump, and also the manual release valve.
This almost always sorts out any creeping issues, if it doesnt, you ll then need to replace the hydraulic pump, but all is not lost as you ll also have fresh seals/O rings in the unit...
Click to expand...

I bought the repair kit so ill see how it goes and updat with the results. Thanks for the replys:cool:
 
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