60 lbs on all 6

[savannah]

i purchased a 1980 2.4 225 merc,the guy said it needed a rebuild.the # 5 piston started scorching.I pulled it all apart and was able to clean that cylinder,put all new rings on and put back together.did test and only have 60lbs on all cylinders.will it even start like this been trying cant even get it to burp.new gaskets all around

[olmo40]

Check you guage on another motor ? or try another guage for a starter.

[ChrisCarsonMarine]

things just dont add up,you should have around 125 lbs/sq in comp in that motor.Re-check with another guage,i doubt it would run at all with 60 lbs,but ive never had a merc consistanyly so low,chris

[tlwjkw]

What kinda rings did ya put in it?

[stvhelm]

make sure the pistons were installed properly. upsidedown? port starboard?

[David Borg]

If you overtorque the heads on that old design head pattern 2.4 you might have warped the cylinders

[savannah]

pistons are correct.is it possible that all the cylinders are warped and how do i fix

[tlwjkw]

What kinda rings did ya put in it?

Are tha new rings chrome or steel?

[john j 80 viking]

had a looper w/ warped cylinders, and that was about the compression i had as well, if you could get it running you'ed be surprised how lean they run and how fast the pistons would melt, don't ask me how i know this:nonod:

[savannah]

i put a magnet to the new rings i believe there steel

[ChrisCarsonMarine]

Chrome bore motors are known to go out of round after a bad overheat,i've seen plenty,but never all 6 cylinders.To end up with only 60 lbs. on all cyls.is very strange,both types of rings are steel,so they would both stick to the magnet,the chromed surface ring is for a replacement steel sleeve ,and even the wrong rings wouldn't cause a 60-70 lbs. drop.Something fishy going on,i think.I thinkmy next move would be to remove a head and use an inside mike to check out of round,chris

[Darkside's Calling]

possibly overbored or undersize pistons installed?? bad reed valves?

[sschefer]

It is strange that all six are identical. The situation is perfectly wrong. Sounds almost like something that would happen if the crank seals got messed up or are missing. Maybe the wrong pistons like was mentioned before. All of them having 60lbs would tend to make me think that the rings were good and probably the only thing that is sealing correctly. I dunno, I'm new to all this.

Did you check the compression with the throttle wide open? If not try it again with a known good gauge (also previously mentioned) and see what you get.

[ChrisCarsonMarine]

you could leave out the reeds and sealing rings and probably not tell the difference.at cranking speed crankcase compression dosen't effect cyl comp much at all.

[TEXAS20225]

all new rings what did you buy for chrome bore /steel bore a friend of mine tried to build a 2.5 200 last year with some Mahle piston that were good with in specs and put on some m1 rings from pro marine in the ceramic:thumbsup: it only developed 50/60lbs at cranking speed he did not continue i gave him some 260 pistons bought some 481 rings from same folks motor is a real strong runner we dont know what happened

[savannah]

i tried a different gauge same reading;The rings i bought from a marine whole saler,they are replacement rings from sierra.Says replacement for chrome bore

[tlwjkw]

Did ya check end gap on tha rings? Sounds like tha block, heads and pistons are just wore out............

[olmo40]

Did you measure anything or check ring end gaps ?? before rebuild ??

[bigshrimpin]

I had one of these early blocks with perfect chrome in all 6 holes tested b/w 60 - 90psi on all 6 clyinders. Put in new pistons and rings and it tested the same on 2 gauges. Finally took it to a machine shop and holes were tweaked. All 6 were out of round. Maybe there is a way to fix the block??? I sent mine to the scrapyard.

[savannah]

i think these holes are tweeked too.gonna bring to machine shop too

[sschefer]

you could leave out the reeds and sealing rings and probably not tell the difference.at cranking speed crankcase compression dosen't effect cyl comp much at all.

Thanks Chris, I wasn't sure if it would or not, I was just trying to think of something they all had in common. Weird that they all read the same like that, you'd think that there would have to be a single common cause. Having never seen it, a tweaked block is kind of hard to imagine but from what I'm reading it seems like it does happen.

Steve

[Superbender]

all new rings what did you buy for chrome bore /steel bore a friend of mine tried to build a 2.5 200 last year with some Mahle piston that were good with in specs and put on some m1 rings from pro marine in the ceramic:thumbsup: it only developed 50/60lbs at cranking speed he did not continue i gave him some 260 pistons bought some 481 rings from same folks motor is a real strong runner we dont know what happened

I think he is on to something here

[tlwjkw]

Tha motor Bobby is talkin about that we put together usin' good mahles and NEW M1 rings. it made about 80 ta 90 lbs. Changed ta stock used rings. Went ta 118 1a 125. Changed ta used GOLD rings went a 120 ta 125. Went to 260 pistons with NEW 481's. Went ta 130, 138. So parts do make a difference. Chrome rings in a chrome hole WILL drop a bunch in a mater of minutes. Just don't ask how I know. Was a LOONGGGGG time ago in another life :rolleyes:............t

[jerry1865]

i believe i may be able to offer a clue here.... the rings for chrome are usually made of ductile cast. there are many reasons why this material might fail to hold.
first, abrasion. second, edge deformation.
if i had a good block that went out of round i might consider having it bored round and rechroming. but only because i could do it on -the-cheap.