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1977 Johnson 175 tilt trim troubles

Peace of ship

New member
Hi All,

I'm newbie to these parts so please be kind.

I have a 1977 Johnson 175 horse outboard that I cannot get the power tilt/trim to work correctly on. This engine runs great. I have it on an old deck boat and it scoots right on up the muddy Mississippi river.

I actually have 2 power trim units for this monster and neither works correctly.

The original one will not keep the motor in the up position. It bleeds down really fast. It goes up just fine. When you shift to reverse it lets the motor come up also so I basically cannot drive backwards at all. I have taken it apart and cleaned it and replaced the check balls and filter screen in it to no avail. I also replaced all of the seals on the exterior of the unit so there are no external leaks. I put new seals on the pistons as well. I did not replace the strange piston/valve in the tilt cylinder though as it is very pricey.

The other unit I purchased used and it worked for a month or so but now the trim portion works fine but when you get to the full extension on the trim the pump seems to be bypassing some/most of the flow on the tilt cylinder and won't lift the engine. If you lift up on the lower unit it will lift it but very slowly until tilted almost all of the way up. Once up it holds just fine. I thought perhaps the pump motor wasn't producing enough pressure so I switched it out with the other one and got the same results. I then exchanged the tilt lift cylinder with the other one but got the same results also. I know that there must be a bad seal inside somewhere but I don't have a flow diagram to show me which valve I should be looking at.

Can someone please point me in the right direction? I'd really like to be out on the water right now.

Thanks in advance,
Steve
 
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