Tilt Trim - STP oil additive?

[69MyWay]

At this point, I am of little to no help. If this does not work out with Rock, the best I could tell you is to start another thread with appropriate title and post a bunch of images. Somebody here will know what you need to hear.

Good luck!!

Got the parts from Rock yesterday - had a buddy that lives fairly close that picked it up for me, and I got it this morning from him. Now I have options!

[69MyWay]

Update....

We ended up taking four different cylinders and building two good ones. I used a machine shop in Central Illinois that specializes in hydraulics. I'm handy, and could have rebuilt these myself...but frankly have had a bad record in the last number of years getting seals in without damage. So, I defer to the experts. Interesting, the experts tore one of the seals and had to get new ones for the two cylinders they rebuilt. It made me feel better about them doing it - as if they goofed them, I surely would have!

Got them on - drained out the STP - and filled up with 10/30 oil per the instructions. They are self bleeding after running up and down and topping off.

They are working great!

Now - here is the part I'm kicking myself. Somewhere in this thread we talked about putting it in reverse and the engine jumping up out of the water when throttling. (this isn't why I moved forward to rebuild/add STP, etc, but figured it would be a bi-product of new internals to stop the lift up). Turns out, that was my fault! There is a "reverse" lock out knob on the pump. You have to turn it full left to lock. I don't know how I missed that before. So, anybody reading this with a motor jumping up in reverse...check your lock out position!

Now, next thing we learned. While they will interchange, Mercury used different cylinders for different HP ratings. I had the 50 hp models on there all along which was the confusion on why the rebuild kit didn't work. The over 50 hp ones move the same distance and fit in the same spot but use a totally different internal setup. My machine shop can't say based on looking at both why one would be better than the other. I feel better about having the correct ones though.

[69MyWay]

Took the boat out this weekend. Now that the air is all out - and I was able to really run it...WOW! The old ones were leaking down all along and i was having a terrible time trimming it out at speed. Now...I can wide open...and trim till is slides out on top and go like a rocket again!!!!!!! And...NO LEAKS!!!!!!!!!!!!!!

[KIRCHNER]

Got the seal kit on order!

GOOD LUCK. ive never had any luck trying to cure your problem. in fact no one had any success on this site with rebuild, my merc guy wont touch it. said cant fix it. sealsdidnt fix mine, i think something internal fails. hope u get it!

[69MyWay]

GOOD LUCK. ive never had any luck trying to cure your problem. in fact no one had any success on this site with rebuild, my merc guy wont touch it. said cant fix it. sealsdidnt fix mine, i think something internal fails. hope u get it!

I used a local machine shop that specializes in hydraulics and welding. He tore one of the seals during install, pulled it all back out and replaced with a "better" seal according to him. They also made up a rig to pressurize them and put them through the paces before calling me to pick them up. Let's hope it keeps working!