tilt problems with 80hp Merc

[captain_cooke]

G'day all,
I have an 80hp Merc (81 mod I think) and the motor wont lift up unless I physically pull on it whilst someone else holds the switch. Once it has lifted, it will slowly drop back down...unless..I then use the switch to lower it. Once I do this, I can then lift and lower it with the switch. It seems like the system needs to be pressurised before it will engage, however, after a short period of time it will gradually drop back down again to its lowest position. If I play with it every minute or so whist underway, it will respond accordingly but if I forget then I have to go through the manual lift proceedure again. Needless to say it's driving me nuts. I have checked the oil levels and all is good there. There is a bleed screw at the top of the pump that I have opened and no air seemed to come out. Is there a bleed screw on the pistons themselves that may need to be opened? I asked at my local boat shop and they said to just keep raising and lowering the motor using the switch and every now and then open the bleed screw on the pump....this hasn't worked and I am hoping someone can offer some advice that may help.
many thanks.

 

[Laddies]

Re: tilt problems with 80hp Merc

If the manual release on he bottom of the pump is screwed all the way out then it sounds like a bad cyl or even both are leaking

 

[captain_cooke]

Re: tilt problems with 80hp Merc

Thanks Laddie,
is there any way to test this? I don't seem to be losing fluid. If I use the switch to tilt up and down (before I've manually lifted the engine) I can see that the hydraulic hoses near the engine move a little when I press the tilt down lever (I beleive this indicates that there is pressure in the system) however when I try to tilt up, no hose movement occurs, not until I've given it a helping hand. One of the lifters has a stainless steel bracket with a screw in it but the other side doesn't. Is that screw a bleed screw and should I have a go at bleeding it? If so, what is the correct way to bleed the system? i.e. should the motor be raised when the screw is losened then lowered and the screw tightened?....I'm pretty sure that is not the way but would appreciate if someone could give me the right method...If it's anything like car brakes then it should be something like...raise the motor, losen the screw and let the air out, then retighten the screw before lowering the motor, repeat that a few times, then raise, lower a few times without losening the screw, finally releasing it and retightening it with the motor raised. makes sense to me but I don't know much about boats and I wouldn't want to do something that could make the problem worse....again, any help would be appreciated.

 

[Chris1956]

Re: tilt problems with 80hp Merc

CC, There are actually two bleed screws on each cylinder. The ones on top of the cylinder are for bleeding the "down" pressure lines. There are two more next to where the hoses attach to the cylinders. These are for bleeding the up pressure lines. They must face up to allow the air bubbles to wok their way out.

You might try to bleed the cylinders first. You will need to unbolt the cylinders and face the bleed port up, to bleed the "up" side. The pump is self-bleeding. Just keep topping it off with 5W30 motor oil or tranny fluid, whatever it has in it at this point. if it still won't hold pressure, you probably need to rebuild one ot both of the trim cylinders. The seals are replaceable.