Merc 850 Port Trim Cylinder leaks

[Nial]

Hi there
Yesterday I trimmed my 1976 Merc 850 up at the boat ramp then noticed the motor slowly let itself back down again after a few minutes. I then noticed the left ram/cylinder was leaking fluid quite rapidly when the motor was all the way down. I was still able to wind the motor up and prop it up for the drive home with the yoke but when I took the yoke out the motor would go down on its own and fluid would leak out from the bottom of the left ram where the smaller pole goes into the cylinder. The motor details are:The serial number
> for the engine is 4366928 and it is the model with electronic
> ignition (NO distributor). Does anyone know what seal I would need to replace in the cylinder and where abouts I could get one from. Also how much I am looking to pay to have this repaired. Thanks
Nial

 

[Chris1956]

Re: Merc 850 Port Trim Cylinder leaks

Nial, There is a 3/4" ID oring seal which has gone bad in your motor. I have been searching for a aftermarket replacement for it, but standard orings do not last long. You can buy a reseal kit the the cylinder ($40) from Mercuy, which has replacement seals for the entire cylinder. A special tool is necessary to replace the teflon piston seal. You may be able to buy the o-ring seperately, since (I think, not sure) it also fits driveshafts for Mercruiser Alpha - 1 Gen 1 units, as well as some older mercury OBs (maybe even yours). It also comes in the waterpump repair kits.

 

[Nial]

Re: Merc 850 Port Trim Cylinder leaks

Thanks for the reply. I'm going to see what the outboard wreckers have today. Do you think it is worth trying to repair it or just buy a second hand one. I don't really like buying stuff from the outboard wreckers because they charge the earth for old used parts but i worth have to tools etc to fit a re seal kit (if I can even find one).

 

[jheron]

Re: Merc 850 Port Trim Cylinder leaks

I would just rebuild them. I did both of mine and they weren't so bad
I used the complete kits from mercury. As for the special tool all you need is a dremel :devil: If you decide to rebuild I will explain the procedure in detail... I think I have allready if you try a search...
Regards Jon

 

[Nial]

Re: Merc 850 Port Trim Cylinder leaks

Can you let me know how you did it? I'll do a search now but i have been searching the last few days and haven't found anything yet. One place has quote me roughly $200 but they can't gurantuee it because if the rod is bent or scratched it will just ruin the new seal.

 

[jheron]

Re: Merc 850 Port Trim Cylinder leaks

The special tool is to insert the teflon slipper seal into the cylinder. The tool is just a little ring with a taper on the inside to allow you to push the seal in without damaging it.
Look at the ends of the cylinder and you will see that there is a little bit of a taper on there already. If you look at the ram travel you will see that the seal cant go all the way to the top or bottom of the cylinder, cant remember which one but it will be obvious when you are looking at it. So just take your dremel with a nice smooth grind stone and make a nice taper rite on the unused end of the cylinder... it wont take long at all also try and keep the taper as smooth as possible so the seal wont hang on it when inserting. Also use lots of oil when assembling them. I did mine in an afternoon last year and I now have 108 hours on them with no leaks.
Regards Jon

 

[Nial]

Re: Merc 850 Port Trim Cylinder leaks

Thanks for the info. Any ideas on what i should pay for a second hand cylinder? I found a guy on ebay in the US selling used ones for $75US. They want $200AU here in Australia for one. One place wanted $550AU for used one as well.

 

[Chris1956]

Re: Merc 850 Port Trim Cylinder leaks

Nial, The used cylinders are around $75 in the US, as you saw. If your piston seal is good (they do not fail too much), you can simply replace the oring. You need a spanner to "open" the cylinder. I made one out of two six inch pieces of angle iron, and three 3/32" screws and nuts. Drill 3/32 holes at each end of the angle iron pieces. Bolt one end of the angle iron to the other. put bolts and nuts through the holes in the other end of the angle iron, such that the ends of the tool will fit the two holes on the bottom of the cylinder, and you can turn the end cap to open it.

 

[jheron]

Re: Merc 850 Port Trim Cylinder leaks

Be careful buying used ones i bought 3 and they all needed to be rebuilt! :| it was a big waste of money buyng the used cylnders once i realized how easy they where to rebuld...
For the spanner i used a universal spanner wrench for the nut on hand held grinders...

 

[jheron]

Re: Merc 850 Port Trim Cylinder leaks

__

 

[Nial]

Re: Merc 850 Port Trim Cylinder leaks

Found a wreckers that will sell used cylinders for $100AU. I guess it pays to shop around. 1st quote $550, 2nd Quote $200 and 3rd Quote $100. I would prefer to rebuild the cylinder but since they can't guarantee it in case the shaft is scatched or bent i think i'll go with the second hand one for now. Can any show me a link to the rebuild kit cause since i'm gonna get a second hand one i might try rebuild the old one myself that way if i ruin it it is not big deal.

 

[Nial]

Re: Merc 850 Port Trim Cylinder leaks

I bought an angle grinder spanner tool but the cylinder is too tight for me to open. I was turning it anti-clockwise but i got no where. Is there a trick to these or would it just be done up really tight? Anyone got any ideas on how to open it cause I bought a second hand cylinder for $60 but it leaks in the same place as my busted one. Also where can I get the rebuild kit from?
Thanks
Nial

 

[jheron]

Re: Merc 850 Port Trim Cylinder leaks

You can get the kit from any merc dealer. Anti-clockwise is correct.. I put my cylinders in a vice and tapped the spanner with a piece of hard wood to get them loose...
Do you have a fax nunber? If so I can fax you the paper that came with my kit showing all the parts and the instructions...
Regards Jon

 

[Nial]

Re: Merc 850 Port Trim Cylinder leaks

Can you fax it to +61 0747740754 and put Att: Kate on it cause i'll get it sent to my girlfriends work cause i don't have a fax number. Thanks again.

Nial