help I'm gona tear it down

rsgonza

Seaman
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Feb 18, 2002
Messages
72
I'm a ford senoir master tech and have torn down an older 2 stroke merc.my questions this see lower topic stalling 90 hp and knocking well the knocking seem like a piston slap.comp is 130 all .can I have good comp and still have piston noise,I bought some gallon baggies a few small ice chests and the book.I have studied book now can I remove the cyl head to inspect pistons or do i have to remove powerhead also were can I get good qulity parts for cheap. and lastly any good tips I should know.please help.its a 2003 90 hp eltpo
 

jimg984

Chief Petty Officer
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Jul 16, 2007
Messages
403
Re: help I'm gona tear it down

with 130 compression,,,,,, could be carbon on top of piston,,, wrist pin,,,if its carbon may could use seafoam, prob best to remove head
 

rsgonza

Seaman
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Feb 18, 2002
Messages
72
Re: help I'm gona tear it down

thanks for the reply so is the head pretty easy to remove? mabye it is carbon build up boy that would be great.is there a way to test wristpin.we tested rod bearing play be putting cyls on tdc and pushing down on piston with a wooded stick all rods seemed tight.
 

CharlieB

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Apr 10, 2007
Messages
5,617
Re: help I'm gona tear it down

That is NOT a cylinder head.

It is simply a cover for the water jacket, cooling the cylinder black/head ONE PIECE casting.

Pistons/rod assy is installed from the bottom side before the crank is set into place.

Look up part details here

http://www.mercruiserparts.com/selectSerailRange.asp?doc_nbr=90+(3+CYL.)

Use a stethoscope to better locate this noise.

K.I.S.S. Start with the basics, Check spark intensity on all cyl's.

Check ignition timing with a light, plugs out, wires connected to a spark tester, remote starter switch, check timing at an idle and again at wide open.

Repost your findings.
 

CharlieB

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Re: help I'm gona tear it down

Oh, and try to keep it all together in ONE thread, multiple threads on the same problem are frowned upon.
 

rsgonza

Seaman
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Feb 18, 2002
Messages
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Re: help I'm gona tear it down

ok I'll do that.I have used a stethoscope and the noise is most noticable in between pistons 2 n 3 now thats having scope on or near back of block casing.[bottom of cyl.I have a so called boat tech listen to it. and he was kinda baffled by noise,its pretty loud when idleing,by taking off that cover you mentioned will I be able to see anything?
 

j_martin

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Sep 22, 2006
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7,474
Re: help I'm gona tear it down

I'm a ford senoir master tech

I'm not sure bailing wire will work on a Mercury outboard. :D

If you take the cover off, you will see the inside wall of the water jacket.

There is an instrument called a bore-scope that will enable you to eyeball the cylinder walls and piston top through the spark plug hole.

hope it helps
John
 

CharlieB

Vice Admiral
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Re: help I'm gona tear it down

Pull all three spark plugs, bar the motor over by hand on the flywheel and inspect the piston domes, one at a time.

Repost your observation of color and consistency. Hopefully you will find dark carbon deposits, wetted at the perimeter, dry in the center. Not pitted aluminum color, if so then remove the exhaust plate, gasket, inner plate and gasket and inspect the side of the damaged piston, bar the engine over, lower the piston below the exhaust port and inspect the cylinder wall for scratches.

That earlier loose carb mounting bolt may have allowed an intake leak, leaning that cylinder enough to overheat that piston, partially seizing enough to wear the piston skirt just enough that you now hear piston slap. If so, you're lucky it didn't seize hard and kick that rod out the side.

If the cyl wall is not scored you may clean the alum off the wall with a scotch brite, very lightly hone and get away with a new standard piston and rings.

OR

Run it until it really needs to come apart, when compression begins to fade.
 

rsgonza

Seaman
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Feb 18, 2002
Messages
72
Re: help I'm gona tear it down

Charlie B your prob dead on,Thanks for reading many posts.The lower carb botl that was off,I have ben told that by the my buddy who does boat repair during the winter and guides all week long.I think you are right.A lean cyl air leak wld cause that piston skirt to overheat.My compression is good as a matter af fact I went out after that noise because I thought the oil pump went out .so I did run it after I cleaned and installed the carbs and it ran great with the exception of that noise.and Like I said it seemed to go away at higher rpms.boy I sure hope thats the problem.now if it is and if the cyl walls are ok should I buy all new rings for other pistons?Thank you very much for your help.I shuld know this weekend what it is.
 

rsgonza

Seaman
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Feb 18, 2002
Messages
72
Re: help I'm gona tear it down

I removed the powerhead and charlie b seems like you were right on all pistons have good comp all pistons are wetted and dryish in the center with slight carbon buildup .my prev post I had a carb bolt come loose on cyl#3 well that piston is damaged not bad but it is scored,cyl #2 also scoured cyl walls still have cyl cross hatch hone but 2 and 3 cyl walls are slightly scored.now to give everyone an idea of the hours on motor I would say in 5 years mabye not more than 250.hours I dont know if that allot or average I do see the engine as being very clean crank rod bearings are clean.[do I have to replace them] all the crank and pistons turn very freely with plugs off.so theres not kind of binding or roughness before i removed a piston.also comp was all 130.cyl to me seem like I could clean them up.I will take block to machine shop and have it checked.my questions are,I posted before I screwed up by using oil that was both cheap and the last bottle had the cap off for a week or two so no telling if it had water in it.My stupidity.now I'm not sure why number #1 cyl looks so good and #2 is piston is scoured a little #3 I can see it leaning out overheating.mabye number 3 overheating got 2 hot being it is right next to #3 cyl damaging piston?if cyl"s are ok can I install new pistons and rings ,water pump thermostat,fuel pump and nec,gaskets or sould i replace all bearings.?im not trying to be cheap I just see no wear on crank or bearings.any suggestions...
 

Faztbullet

Supreme Mariner
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Mar 2, 2008
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15,589
Re: help I'm gona tear it down

If you have some inside mic's, mic the cylinders. Start at the bottom of cylinder(spark plug end) and measure at three places and record results. Move to the middle around ports and repeat. Also go 1/2 inch in cylinder and repeat. Standard finish bore is 3.500. If cylinder is more than .003 out,that cylinder needs bored. Make sure the machine shop uses a boring bar and not a honing machine to bore cylinders.
 

rsgonza

Seaman
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Feb 18, 2002
Messages
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Re: help I'm gona tear it down

thanks for the tips,I have one more question.before I tore the engine apart I could spin the flywheel with plugs out of it and the engine would continue to spin about 90 degrees,very free,and comp is still at 130 psi.now I removed one rod bearing and it looks great,I understand I should see mabye alum particles but the engine is clean except for the slight scouring.one can can I replace the piston without removing the other rod bearings?well I guess I should just inspect them right.but can it be done I will post pics.there a plastic little bleed valves?I think thats what they are should those be replaced.and the rod bolts are tourqe to yield?correct.I will try post pics ok thanks
 

Faztbullet

Supreme Mariner
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15,589
Re: help I'm gona tear it down

Pull the crank out as a assembly, that way you can inspect the other cylinders. If you left assembled, how are you to hone it without honing debis/grit getting to other cylinders ? And how are you gong to wash that cylinder? Also you are going to have to remove the other caps to remove crank to replace bad piston anyway ,so inspect all,replace whats needed,rering all cylinders and all should be fine.
 

rsgonza

Seaman
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Feb 18, 2002
Messages
72
Re: help I'm gona tear it down

http://s267.photobucket.com/albums/ii310/rsgonzales/Boat engine pics/?albumview=slideshow


Thats a link to the pics we found num 1 cyl in good shape and #2 and 3 in bad shape crank looks good,does it look like they got hot?any feedback would be apreciated.also any reasonable parts web sites.for my 90 hp 3 cyl merc.#1 looks reaaly good I thing mabye the loose bolt cause the lean cond in # and it gt hot? one other possability is I am nt gona lie I did hear a faint sound under the console.mabye the warning horn is out but I head a faint sound when the engine was stalling,then if you follow my posts I cleaned carbs and it ran fine except for noise.also the 2 cycle oil I used had the cap off of the gallon jug so it cld have had mabye a bug,or water.? the pistons dont look blue like they got hot also this one tech said if water pump had gone out [its new] or thermostat #1 cyl wld have been affected .can I please get a good parts place to get my parts.Thanks
 

rsgonza

Seaman
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Feb 18, 2002
Messages
72
Re: help I'm gona tear it down

I dont think the engine got hot .mabye it leaned out juding by the pics[prev post can someone explain why this may have happened,its cyl #3 and #2 now if you read back on my prev post this all started when my boat started to stall.I took to cleaning the carbs and found the lower bolt holding carb off.the engine still had good compression and as you can see the pistons cracked.thats were my piston slap noise came in.again i'll add I remember adding oil one morning from a bottle of 2 stroke oil that had the cap off.poss. for 2 weeks so it may have had a bug in ther or water.I have since cleaned all oil injection parts and lines and carbs and checked oil pump seems ok please anyone.
 

Faztbullet

Supreme Mariner
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Mar 2, 2008
Messages
15,589
Re: help I'm gona tear it down

For some reason cannot view your pic's. The tech is correct that a water problem would affect #1 and the others also. I use ProMarine for parts:www.promarineusa.com.
The parts you may need are: (Pro #'s)
#6200 Std. piston
#6215 .015 piston
#321 Std ring
#WP42-1 Qty of 3 wrist pin bearing
#012-1 Qty of 3 rod bearing w/cage
#307 lower crank bearing
#2017 crankshaft seal kit
#004 gasket set
#235 can of peanut butter
#GS1 Gel Seal
#9740 bearing grease
 
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