merc 850 trim tilt diagnosis?

[MercMark]

1973 merc 850 with tilt and trim.<br /><br />The tilt currently works entirely and will hold the motor up. The trim leaks down under power.<br /><br />I was wondering if this is any indication that the problem is in the cylinders or check valves in the pump.<br /><br />Most of what I read in the manual involves cleaning all the valve seats in the pump first then if that doesn't work look at the cylinders.

 

[WillyBWright]

Re: merc 850 trim tilt diagnosis?

Yeah. Without the pressure testing apparatus, that'd be the best course of action. But first, make sure the manual relief knob is turned fully to the left.

 

[Chris1956]

Re: merc 850 trim tilt diagnosis?

MercMark, I do not know an easy test to determine if the piston seal in the cylinders is bad or the valve body is leaking. However, you can narrow it down as follows:<br /><br />The cylinders are connected in "series", such that if one has a leak in the piston seal, the motor will "leak Down". If you disconnect one cylinder and plug the lines, and the other one holds pressure, you will have found the problem. If it doesn't hold pressure, reconnect and bleed it, and disconnect the other cylinder. If it still doesn't hold pressure, it is likely the valve body.<br /><br />I have had two piston seal leaks in 25 years, and no valve body failures. You can probably still get the cylinder repair kits from www.dougrussell.com, however a special tool is necessary to install the piston into the cylinder. Alternatively, if you can find a used cylinder, it should be cheap enough to just replace it.