Tach & Power Tilt not working

I have a 1984 Johnson SeaHorse 50HP Model number J50TLCRM on my bass boat I just bought. I've been told it is the commercial version for whatever that means as I am new to all this boating stuff. It runs great so far with only a few minor issues with the boat itself. It's a 1984 Glasstream 15ft bass boat on a LoadRite galvanized trailer which is in great condition for as old as it is. Is there a big difference between the commercial version & the regular version Johnson outboards?

My problem is two fold. First my tach does not work at all & I have no idea what the wiring connections should/should not be or what colors or even where they connect in the system. I'm trying to find a repair manual for this engine but no luck so far. Does anyone know what the wiring connections should be & how to check out the system?

My other problem is the Power Tilt & Trim. It goes up & down fine everytime but it will not stay in the up or trimmed position. It starts going back down on it's own. I have checked for leaks but have found none. I have no idea where the fill hole is located on the system to check to see if it is low. Anyone have any idea where to look or what my porblem might be? I suspect(?) the hydraulic cylinders might need rebuilding as I think the inner check valve or seals may not be working correctly.

I'd like to say in advance that I appreciate everyone's help so far on this board as I haev been able to learn a lot & I do appreciate it very much. This is the BEST SITE I have found for people willing to take the time to help others who are trying to learn.

Re: Tach & Power Tilt not working

is it charging the battery? Tach gets its signal from the rectifier -- if the rectifier fails, the battery stops charging and the tach gets no signal.

if the tach does not move to zero when you turn the key "on", it means tach isn't getting 12V, or else a bad ground.

tach wiring: SND = gray wire, IGN = purple, GND = black. LT is gauge illumination, tie into another gauge or whatever you have for helm lights.

your tilt & trim: I have a '79 with "power tilt", but no trim. If you have only one tilt cylinder in the middle of the bracket, that's what you have as well. It won't hold up once you get up much over trolling speed. Cause it has an emergency relief valve, to let the motor kick up if you hit an obstruction.

If you also have the two trim cylinders, they should hold the motor up.