Tilt Trim - STP oil additive?

**69MyWay** · 03-18-2019, 08:36 AM

Hello all! Getting ready for the warmer weather...and starting to mess with the hold Viper. It has a 1979 115 Merc. The tilt/trim sags down after a bit when raising the motor. I've read numerous threads about this last year.

I'm not prepared to rebuild or replace parts right now. I did replace the lines...and fluid as well as replace the relays and wiring on the unit when I had it all out last year.

I read somewhere that somebody had added some STP to the oil to put a bandaid on it for a while. Well, yesterday I sucked out 240 cc of the 30 weight oil and replaced with STP stop leak and oil conditioner.

Guess what? Motor stayed full up right all night long with only about 1/8" drop at the ram rods.

It was about 50 degrees when I put this in - thick as honey. It will thin out in warmer weather.

I noticed the motor moves up and down a bit slower - but moves none-the-less.

I may go back and pull some of this out and thin it down with more 30 weight.

I realize this isn't a fix - probably needs the ram rods rebuilt and or pump valves rebuilt (a lot of $$$ on both of those) - but maybe this will work at least through this coming season. I'll be lucky if I can get the boat out a dozen times this year. Hopefully doesn't burn out the motor! I just wanted to share in case anybody else is curious about trying this hack. Yes, it is a hack and fools gold in the long run.

**SS Minnow** · 03-18-2019, 12:21 PM

And potentially dangerous depending on where and how you run. Hope it works out.

**69MyWay** · 03-18-2019, 01:36 PM

Originally Posted by SS Minnow

And potentially dangerous depending on where and how you run. Hope it works out.

I didn't think there would be any danger...outside of being stranded with a broken hydraulic system.

What is the danger concern? It won't take but 20 minutes to suck most of that back out.

**SS Minnow** · 03-18-2019, 04:28 PM

The only danger would be in the system failing. If you operate in certain places, that could be the hazard. I had hydraulic failure once that would only let you use reverse at a very slight throttle or the motor would lift itself out of the water and then slam back down on transom when you let off gas.

If you are just on little inland lakes or calm streams/rivers with no shallows, you will be fine.

**eli** · 03-18-2019, 06:00 PM

When it’s 80 out might be ok will thin down some and might start leaking down again then you will have to fix might as well do it now your call sucks driving around with motor tucked in you could put a clamp pin to keep motor level hole shot will suck

**Euroski** · 03-18-2019, 06:22 PM

I would try 80-90 gear oil over STP.

**flabum1017** · 03-18-2019, 08:16 PM

Or ATF to make the seals swell a bit

**Capt.Insane-o** · 03-18-2019, 11:00 PM

Lucas power steering juice.

**69MyWay** · 03-19-2019, 07:28 AM

Originally Posted by SS Minnow

The only danger would be in the system failing. If you operate in certain places, that could be the hazard. I had hydraulic failure once that would only let you use reverse at a very slight throttle or the motor would lift itself out of the water and then slam back down on transom when you let off gas.

If you are just on little inland lakes or calm streams/rivers with no shallows, you will be fine.

Hmmm, interesting - it currently does that (the lift and slam in reverse thing) PRIOR to adding the STP. Very annoying.

When it’s 80 out might be ok will thin down some and might start leaking down again then you will have to fix might as well do it now your call sucks driving around with motor tucked in you could put a clamp pin to keep motor level hole shot will suck

I hear ya - wish I could. Don't have the extra cash right now to put it in the hydraulics. I've seen rebuild kits aren't that bad...BUT, I've got a terrible track record with seals and shafts. You should see what I did to my 1988 Military Humvee steering gear box when I tried to rebuild that.

This fall/winter I hope to hit it all new - I had planned on redoing the much needed tattered and torn seats this last winter, but my dog had surgery and wiped out my money reserves.

Or ATF to make the seals swell a bit

I would try 80-90 gear oil over STP.

Lucas power steering juice.

I thought it odd that these pumps use 30 weight engine oil and not steering or ATF. I'm a HUGE fan of Lucas. I've seen it do wonders. I spent a lot of time reading all the labels. This STP was specific to worn seals/leaks...and of course being a thicker agent - 80/90 was my next choice.

I let it sit for 24 hours, and it maybe dropped 1/4 total. Before, it would fall all the way in 4 hours. So, it is doing something...

**SS Minnow** · 03-19-2019, 07:43 AM

Originally Posted by 69MyWay

Hmmm, interesting - it currently does that (the lift and slam in reverse thing) PRIOR to adding the STP. Very annoying.

Have you had the boat on the water yet to confirm that it no longer does this now?

I would serious look into fixing the problem, now. Plenty of time til boat season where I am. Heck, everything is still froze over.
If you just take your time, do not let yourself get frustrated and be capable of walking away, you can do it right.
Do not be afraid to get the right tools compared to "using" what you have. A lot of specialty tools are available for rent from local auto stores. The ones by me rent for no charge if you bring the tool back in 60 days. And most importantly, there are a few people on here with a ton of experience with those old towers. Somebody will walk you right through the project, you just need to find them.

Either way you go, good luck!

**Capt.Insane-o** · 03-19-2019, 09:09 AM

My xs would bleed down over a couple hours...we were getting ready to go to dale hollow for a couple weeks so i just flushed it out with mineral spirits and refilled it with 10-30 and a small bottle of lucas power steering conditioner. Worked fine for the next year. Resealing kiys for the cylinders are pretty cheap though.

**eli** · 03-19-2019, 09:56 AM

Paying vet for surgery can be costly for sure

**69MyWay** · 04-01-2019, 07:47 AM

So...guess what? it sprung a leak on the left rear cylinder. I assume the thick fluid pushed it over the edge - but ironically I expected it to stop any visible leaks. This is the first leak I've ever seen on the system.

So, making calls and looking around now for seal kits and or a pro hydraulic shop to make it right.

I'm okay with it moving slow - even sagging - but not leaking through this season.

**SS Minnow** · 04-01-2019, 09:13 AM

Leaving a rainbow trail in the water by me will get you an expensive ticket from the DNR.
Probably more then it would cost to take to someone else to fix.