Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

[tigerlegend2000]

does anyone know the average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke?... i did a compression test on mine over the weekend and
this is what i got: #1 35psi
#2 0psi
#3 to #6 50psii
i read through the forum and acknowledge that it should be 100+ , just wonder maybe mine is old engine just black smoke coming out ('cause 2 cycle engine), note that engine start right up at idle speed... any input will appreciated! thanks

 

[samm835]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

I am sure others will chime in here, but yes you definitly want better than 100 on your readings. Are you sure you did your reading correctly? If you only got 35 and you say its running I think you did something wrong. Try again and let us know what you got. But to answer your question you should be getting at least 100 on each.

 

[Droll]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

Recent tested engines:

• 1982 115hp 125 > 127 psi
• 1984 115hp 125 psi ( not broken in yet, running time under 1 hour )
• 1986 115hp 120 > 125 psi ( had water issues... )

Other gauges might give different reading but this should give you something to compare with


Arne Kjetil

 

[Chris1956]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

If that motor runs, you probably did the test incorrectly. Normally you spin the starter with the gauge pushed (or screwed) into the spark plug hole and wait for the gauge to hit it's highest reading.

 

[jimg984]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

all plugs out, turns more freely

 

[Moody Blue]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

all plugs out, turns more freely

With compression readings like that, it should turn over quite easily with or without the plugs in

Seriously though, something aint right. Even if the numbers are low across the board, the "0" reading on #2 is cause for concern.

 

[tigerlegend2000]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

ok... follow up... i got another set of compression test ... reading as follow
#1 130psi
#2 0psi
#3 through #6 130psi (tried with 6 cranks at each cylinder)
then i poured some oil on #2 got 35 psi out of it. Next, i blew 100 psi of air into its cylinder, no air coming out of the carb (so i assuming that intake valve of #2 is ok)... but air leaking from the exhaust in the prop. where do i go from here? can i just replace the rings on #2 and how hard is it? where can i get parts? thanks again for any input....
also, is there any alternative away to fix witout taking the engine apart? chemicals?

 

[kartman]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

sounds like thats a dead cylinder. about what happened to mine. your next step would be buy a manual, and tear it down. no chemical will fix that. and for parts, you can get them here on iboats.

 

[tigerlegend2000]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

Do you guys think i could use this outboard 'til the end of this season? without damage to the other cylinders or crankshaft? i want to fix it as my winter project? i don't care if it smoke a lot? thanks

 

[samm835]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

well you can use it if you want....but I would highly suggest that you don't. You will beat it to death, plus you won't get any performance out of it. It could also leave you stranded. Also if you take it to fix now, much cheaper than if you want any longer or if you use anymore.

 

[James R]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

Continued running of a motor with a dead cylinder will cause more damage and make the repair more costly.

 

[tigerlegend2000]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

ok... i think i'm going to tackle this job (will miss a couple of weekend for fishing )... what do you guys think about mercury OEM piston's rings or aftermarket like Sieera? which will last longer? is there any kits for rebuild (hence, i'll take averything apart so i need gaskets, seals...etc )? my outboard engine is Mercury 115 HP inline 6, serial # is 66306XX, i believed she was borned in 1985. Can anyone guide me or give me links to get parts?
thanks in advance

 

[Chris1956]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

Pistons rings and gaskets for that motor are avail from many places. You can shop around and save a few $. You will need one oversize piston and ring set, and a machine shop to bore #2 cylinder. You will need a powerhead base gasket as well. Do you know what caused the damage? You should clean and rebuild at least the top carb, the fuel pump and replace the waterpump impeller.

The repair will cost about $250 in parts and machine shop cost, plus your labor.

 

[tigerlegend2000]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

rebuilt is the way to go right...? So the engine is aparted, #2 is junked (see pics), there is scratches on the #2 cylinder wall, my brother who is a car mechanic help me hone the wall... still feel a little bit after honing... i might go with this option... can't not find any machine shop to bore #2 where i live... pick up a new piston and he said only piston with 2 rings available (unlike the 3 rings piston that i have now) i took it anyway and move on...... i will post step by step and pics so newbie like me can learn more... will updated...
Sorry my images are too large... and i don't know to shrink them at this moment..... will post pics later on...

 

[Droll]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

there is scratches on the #2 cylinder wall, my brother who is a car mechanic help me hone the wall... still feel a little bit after honing... i might go with this option.

You can get away with a light home IF the cylinder still are within spec
Out of round/Tappered/Worn no more than .003" > .004"
( Standard bore are 2.875" )

pick up a new piston and he said only piston with 2 rings available (unlike the 3 rings piston that i have now) i took it anyway and move on......

3 ring pistons are available from Sierra and ProMarine, I would prefair to use 6 identical pistons, but it will run ( You got the low dome piston I assume ?? ), just stay away from inline pistons from Wiseco ...

Sorry my images are too large...

Can't see any images...



Arne Kjetil

 

[tigerlegend2000]

Re: Average PSI reading for 1985 Mercury inline 6 cylinders, 2 stroke...?

here are the pics of cylinder#2 and the block... let me know if you guys can see the pics.... about the 2rings piston... the only reason i got it (double the price online) 'cause i rather see and measure right @ the counter... i'd bad experienced when ordered online and they send me the wrong parts, wasting my time called, sent back, etc... also, i read here that i'll be ok if i use 2rings anyway... i will be clean the blocks, intake, pistons and exhaust tomorrow... wife and kid made me stay away from the engine this whole weekend , but family go first, right? , whoever got family should understand me.... will do follow up and pics thanks all