Power tilt and Trim for Nissan NS70A

mccarlej

Cadet
Joined
Apr 24, 2017
Messages
24
I just purchased my first boat and I am having trouble with my power tilt and trim. My boat is an ebbtide dynatrack 156 ss with a Nissan 70 HP NS70A motor on it (yes i know parts are virtually impossible to find). The motor itself is great. All it needed was a fuel pump that i can get from singapore and bam its running like a champ. The seller was upfront with me about issues with the PTT. I unscrewed the manual screw/filler plug and it was extremely low. I have filled it and the electric motor runs fine both up and down. I can hear it moving fluid and i removed the bottom plug and ran the trim to see it discharge fluid. I think i am not bleeding the rams correctly but i have tried both loosening the lines on the rams and the manual screw to remove the air. no matter what i do, i cannot get the hyds to hold the weight of the engine. i have been able to get it to lock in the down position but it leaks down if i manually lift it. Also, the rams are not moving when i run the PTT. If any of you have any knowledge i would be very grateful. Thank you for your time.
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,500
As on p34 of the owner's manual, start by checking oil level with the plug out, and top up. Use Dexron II or equivalent ATF. Power the motor up. stop, open the manual valve 1/2 turn, and lower by hand. Then close the manual valve, top up, and power up again. This will take time... at least a half-dozen cycles. The manual valve is different from the filler plug; the plug is on the side of the cylinder, while the manual valve is on the valve body. Patience.
 

mccarlej

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Apr 24, 2017
Messages
24
Paul, thank you so much for the reply I'm just looking for clarification here. On the side of th motor there is a sticker above the screw that says "manual release" this is the highest opening to fill as there is no reservoir. The bottom of the motor where the line is coming out there is another screw/plug is this the manual valve you are talking about to turn 1/2 turn? Please excuse my ignorance this is my first boat. Also the motor will not "run it up" at this point. I have to raise and lower the unit by have to move fluid in the system but as in the OP the motor is definitely running so I know it's not an electrical or motor issue. Thank you again for your help.
 

mccarlej

Cadet
Joined
Apr 24, 2017
Messages
24
Update: after trying the method above this is what I experienced.
After turning the manual release valve and lowering the motor I tightened it back down and was still able to move the motor by hand. Also, the left actuator now shows a small leak coming from the seal around the piston rod. I know I need new seals in at least one actuator. But with manual valve in or out I can move the motor by hand. When I run the hydraulic motor I get no movement whatsoever. The leak is very small. I have also been able to hydraulically lock the motor down but not up after a lot of bleeding. Do you think the interior seal is so bad that fluid is just flowing around the rod? Or does it sound like it may still have air? When I manually lower the motor I can hear hissing from the actuator.
 

TOHATSU GURU

Admiral
Joined
Jul 22, 2004
Messages
6,164
Probably a little of both. Keep trying to bleed it. if that doesn't cure it think in terms of where you can find an old 50C, 55B, 60A or 70A you can get for parts. Then start thinking about what constitutes a money pit. I really loved that model engine, but you do not want to develop an emotional attachment to what has become a relic.
 

mccarlej

Cadet
Joined
Apr 24, 2017
Messages
24
You are probably right. I've been looking for a tilt and trim but only one I've found is $1000. I just assumed with the minimal leak the rams should attempt to move. Until I figure this out manual lock bar it is. I've even looked into taking it off and disassembling it to get dimensions of seals and rings and start a fabrication project. I know a guy that is an engineer for a hydraulics manufacturer.
 

mccarlej

Cadet
Joined
Apr 24, 2017
Messages
24
No Title

With the rams off I believe I found my problem but I have NO idea how they could have been bent like this. I found replacement rams just negoatiating the price but some might find this interesting.pics attached.
 

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mccarlej

Cadet
Joined
Apr 24, 2017
Messages
24
And now i have everything working and even have some spare parts! Thank you everyone.
 
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