Dampers and Grounding-1995 Merc 115

[richw46]

I have a 1995 Merc 4 cylinder 115 HP. Recently my power trim indicator and tachometer quit working. I checked the trim sending unit and gauge and both seemed OK. I ran a wire from the sending unit up to the gauge but it still didn't work. I knew that it tested OK back by the motor so I started checking grounds. I found that the steering cable was the only place the sending unit was getting a ground. I checked the ground straps on the port side of the motor and found them both loose at the dampers. (I guess that's what they're called. Kind of shock absorbers with grounding cables.)

I ran a jumper from one grounding strap to the other and the trim indicator started working. My question is, these dampers were at some point tight, but now they are very loose. I can turn the bolts with my hand, although they are rusted together, they won't fall off. The grounding straps at this point are loose and rusted, not making contact with the metal part of the lower unit. Do these dampers need to be replaced? Can they be tightened? I can't seem to move them to unbolt them.

Thanks

Rich Ward

 

[al27023]

Re: Dampers and Grounding-1995 Merc 115

Are you looking at the ones under the power head or the ones in the exhaust housing? They are listed in parts list as rubber mounts and the lower ones on mine were de vulcanized - separated between the rubber and the bolt sleeve and a bear to get out in the exhaust housing; had to cut out with a dremel tool.
Don't quote me but it appears to me you have to lift the power head to get to the upper ones. I have not tackled upper ones and probably won't unless it gets a lot worse.
You can go to the Mercury parts website with your serial number, and get parts breakdown for the exhaust plate, which shows the upper mounts.
The lower ones are shown further down under the drive shaft housing parts listing and breakdown.
The ground straps jumper across the rubber joint in each of the mounts to provide continuity, as you learned.
Hope this helps.

 

[richw46]

Re: Dampers and Grounding-1995 Merc 115

It's the lower ones in the exhause housing, shown in the schematic as "mounts" plain and simple. Mine still seem to be in one piece inside the metal housing.

I didn't know if these should be periodically replaced or not. I'm sure they were tight when new and the grounding wires were tight against the mounting bolt heads too. But now the mounts have shrunk (I'm guessing) and the bolts have rusted. Since the mounts have shrunk the ground wires are now loose and rust on the bolts is preventing a good ground so my gauges are acting up. I've added my own jumper wire from one ground wire to the other. Not pretty, but the gauges are working again. There is too much free play in the bolts to expect the ground wires to make a good contact, except when the motor is tilted up.

I'm wondering if I should replace the mounts. The motor runs fine but am I risking anything by not replacing them. Sounds like you had a bear of a time doing the lower ones. Looks to me like it's a matter of removing the mounting bolts then the mounts themselves and reversing the process with new parts. I can turn the bolts with my fingers (they are just spinning inside the mounts). I tried unbolting but couldn't get a good grip on the bolt inside the housing, which is metric instead of SAE.

Suggestions? Let sleeping dogs lie?

 

[al27023]

Re: Dampers and Grounding-1995 Merc 115

Just to be sure we're talking about same item - the lower mount I replaced is just above cavitation plate behind a plastic cover with two SM screws, then under an aluminum cap which was broken on mine (salt growth had frozen all parts together). This will expose the outside of the mount, a steel cylinder vulcanized to a smaller concentric steel sleeve that the bolt goes thru from aft to fwd with a nut at the fwd end where the ground strap is located. Probably what is moving is the bolt and inner sleeve unless the nut (14mmX2, if I remember corrrectly, don't remember wrench size right now) is loose. If the nut and bolt are loose in the inner sleeve you are better off and can probably disassemble with a lot less effort. I had to replace both caps, both mounts, bolts nuts and ground straps just over $105 on 06.
How much does the motor move with respect to transom/pivot bracket, when idling? Can you see a significant shake both at top or at pivot yoke? Based on that and visual condition of upper mount attachment at power head I would decide whether to replace the lower ones - just remember if you hit something in water the lower ones take most of the shock.
Once again, hope this helps.

 

[richw46]

Re: Dampers and Grounding-1995 Merc 115

Your statements are correct and we are talking about the same thing. I noticed increased movement of the motor at the pivot bracket last year but I didn't do anything about it.

There is about 3/8" play on that bolt that's inside that sleeve that's turning freely, which is NOT making a good ground contact and making my gauges go crazy. The steel sleeves seem OK, a bit rusty, but otherwise OK. The rubber is still connected to the sleeve and I can move the assembly back and forth in the area that's holding it. The nut / bolt turns but really seems tight. I tried unscrewing the bolt but it was pretty tight, I may need a breaker bar.

It sounds like it's more work than I want to get into on my own. I can probably do the lower mounts myself but the upper sound like a lot more work. I looked up the cost for just the mount and it's around $60 per side. I'm going on a trip next week. I'll see what develops from that.

Thank you very much for your feedback.

Rich

 

[holbs10]

Re: Dampers and Grounding-1995 Merc 115

This would be a great time to grab a digital camera and post some pics of waht you mean rich. It makes it a lot easier to explain. Also Id like to see too since none of my gauges work.

 

[richw46]

Re: Dampers and Grounding-1995 Merc 115

OK, holbs10, I'll do that tonight and post here. Quick note, last year, maybe year before, the trim gauge started acting like a windshield wiper, bouncing up and down. I left it alone figuring it was minor. Over this past winter it quit working. I did some reading, found the sending unit and tested it, but it was OK. I pulled out the gauge and tested it, it was OK too. What's left but wiring? I ran a wire from the sending unit to the gauge and it still didn't work. Thats' when I started continuity testing for the ground and found the loose wires. When I made a jumper from one to the other, everything started working again.

Rich

 

[richw46]

Re: Dampers and Grounding-1995 Merc 115

This is a shot of the lower left mount. You can see the rear grounding strap and bolt are rusting, although both are in good shape. The straps don't make good contact on both ends of the mount's bolt so I added a new wire between the two of them and the tilt gauge is working now. To test yours you can add a temporary jumper then turn your ignition on to see if the gauge comes on.

I checked the free play and there isn't a lot, just enough to lose ground. I'm going to leave the new ground strap on and add some grease to get rid of the rust (WD-40 then waterproof grease). I'm going for a 5 day fishing trip next week, so we'll see how it works.

Rich

 

[al27023]

Re: Dampers and Grounding-1995 Merc 115

Just curious, what happens when you tilt the motor up?
It appears that you should be able to loosen nut and clean end and install at that point also. Or use a longer lead to allow tilt trim movement, or is this temporary?
Just some thoughts, Good luck.

 

[richw46]

Re: Dampers and Grounding-1995 Merc 115

When tilted, the front part of the mounting bolt gets tight and the rear loose because the weight of the engine is pushing the rear of the mounts. There is really not a lot of play in the ground wire, but enough to prevent contact. I'm going to clean the contacts when I get back from my trip , maybe get a washer in there to make it tighter and better contact. The jumper is just to get me past this upcoming trip.

Rich