Scored Cylinder: take to machine shop or D.I.Y?

[RebeccaBurg]

Wow- what a helpful site!! For those with experience honing cylinders, I took apart my 15hp Johnson (2-st, yr 2000) and cleaned the block. Cyl #1 is scored and I hope to rebuild with the available larger piston size. There's a store on Ebay selling rebuild kits for my motor with .010 oversize pistons. I've never had to hone any of my motors before, so the ? is:
Can my ordinary 3-stone drill operated hone take off enough material in the cylinder to bore it .010 over? (have good cyl. bore gauge to keep track)
Or is it simply better to take the bugger into a machine shop and have 'em do it? if the block is clean and ready to machine, is it not too costly?

another odd thing is that normally, the only available oversize piston for this size motor from various OMC parts dealers is .020 over. How did this one Ebay shop manage to have pistons that are only .010 over??

rebuilding this nice little outboard is far less costly than buying a replacement, if done right, it'll be like having a "new" motor!
thanks for any help,
am learning so much from this!

 

[oldcatamount]

Re: Scored Cylinder: take to machine shop or D.I.Y?

My advice is to take the block to a good machine shop and have both cylinders bored. Trying to do something like that with a hand held hone would very difficult if not impossible. The cylinders are machined to close tolerances and trying to remove precisely .010 by hand is something I wouldn't try. A cylinder hone is more of a "clean up" tool and is very use full but, not for this application. A machine shop (here in Vermont) will charge about $50 to $75 per hole for boring (and honing).

 

[HighTrim]

Re: Scored Cylinder: take to machine shop or D.I.Y?

I have lightly honed cylinders....after some practice on scrap spare powerheads though.

I have not bored one out with oversize pistons. My local machine shop is cheap and they are always perfect, so I leave it to the pros for that. It is not that expensive if you bring them in the block ready to go, about $50 a hole. Well worth the money in my opinion.

 

[GA_Boater]

Re: Scored Cylinder: take to machine shop or D.I.Y?

Before you buy replacement pistons have the bores measured. The score could be deeper than what a .10 overbore can recover. And boring should be done by a shop. It's very difficult it not impossible to do by hand.

Welcome aboard, Rebecca. Enjoy your stay.

 

[Faztbullet]

Re: Scored Cylinder: take to machine shop or D.I.Y?

You can get aftermarket pistons for that motor in .010,.020,.030,.040 oversize, and you cannot hone a damaged cylinder back to being round. I have had several customer bring in blocks that they tried this and some looked good but all where tapered and out of round....

 

[raczekp1]

Re: Scored Cylinder: take to machine shop or D.I.Y?

hi.i d like to ask you how it happened this scored cylinder?
and symptoms from having scored cylinder

few weeks ago i bought 15hp Evinrude 96'
this motor is not burning all part of oil from mix.
i played with termostat to warm up the block more(i just added rubber bushing in termostat assembly)
but still i can see oily spots floating over the boat transom.

if you can drop link to this store with oversize pistons

 

[etracer68]

Re: Scored Cylinder: take to machine shop or D.I.Y?

This should be a no brainer, at $50 or $75 per hole (bored & honed) to fit new pistons, is the way you should go. I'm a tool maker for 30+ years, and yes a very experianced person could hone it out, with a sunnen hone (2 stones plus 2 wear blades). The problem I see is by the time you work the taper, and out of roundness out, you will have worn the edges of the ports to a small taper, or round them to much. I have had alot of experiance on hand manual honing, and I would even think of not spending the money to get your pistons fit by boring and honing by a machine shop. I also would not buy your pistons until you know for sure what they (both will clean up at).

Raczekp1, Have you checked the operating temp, with a good temp gun? 2 stokes dont burn 100% of the fuel/oil mix, even 4 strokes dont burn 100%. I wouldnt play with the thermostats, until you know for sure what temp its running. You could have other issues other then temp.

 

[RebeccaBurg]

Re: Scored Cylinder: take to machine shop or D.I.Y?

Great advice guys!! Thanks so much for sharing your better experience with this newbie. Will be calling the nearest machine shop come Monday...

(what happened was that the motor overheated, something blocked the intake- a plastic bag?- & in matter of seconds it smelled like burned rubber paint. It happened at night, of course, so didn't see water not coming out of pisser. Head slightly warped, but luckily still within tolerance and able to be refaced. Mating surface on block also refaceable. But some deep scores in Cyl#1 and associated piston scored. A friend is coming over to help double check my measurements to assure block isn't warped, cyl's out of round or too tapered, where it's beyond being re-usable. have precision straight edge, feeler gauges, calipers & bore gauge to check the important stuff & assure the thing's re-usable)

thanks again!
Rebeccahttp://forums.iboats.com/images/smilies/biggrin.gif

 

[oldcatamount]

Re: Scored Cylinder: take to machine shop or D.I.Y?

Good luck and keep us posted with your progress.

 

[raczekp1]

Re: Scored Cylinder: take to machine shop or D.I.Y?

i know my problem can be related with compresion isuess and mix is not pulling to burn out in stroke but blowing out to exhaust.
i have 9.9 83' and i think older construction is much better.

 

[jmendoza]

Re: Scored Cylinder: take to machine shop or D.I.Y?

My 1975 was horribly seized before I bought it, but it ran fine. I had no clue it had this problem. The only outward sign was a melted top coil. Upon investigation I found really bad scoring on the exhaust side of the top cylinder, moderate scoring of the bottom, but about 115 PSI compression, so I replaced the head gasket, and thermostat, and ran it that way from 1981 until 2009. Meanwhile, I had ordered .030" pistons, rings pins, and top bearings with all seals and gaskets for a top end rebuild, but somehow never got around to it. In 2009 however I decided to proceed and do the overhaul over the winter. I found it would cost around $100.00 for the boring alone, and so I bought a low time powerhead off eBay for $125 including shipping, from a 1975 Rude, it had 125 PSI on each cylinder. I put new crank seals on it, and all new gaskets, and lapped the head too. My old powerhead sits in a box, it's too expensive to repair, even though I have the parts, especially when there are plenty of good used and servicable ones availlable. Try to find one with good compression , fresh water, and you are in business.

This is testimony to how rugged these Johnsons are, and how underated they are (over built for durability). Some may call me crazy, I will not argue that, but the engine didn't know that and just kept running. One thing I did notice was the new power head gets a little better gas economy, and starts easier when cold.

 

[RebeccaBurg]

Re: Scored Cylinder: take to machine shop or D.I.Y?

Geez, time flies. Happy New year guys! The block was returned from the shop with both holes bored .010" over. those scratches in it weren't as deep as i'd thought. Now just waiting for the .010" oversize piston & rebuild kit to arrive in the mail. The Holidays really delayed this job, lucky for me a friend is letting me use his motor in the meanwhile...
can't wait to put humpty dumpty back together though!

 

[HighTrim]

Re: Scored Cylinder: take to machine shop or D.I.Y?

Us boaters up here in the great white north dont want to hear about your "problems" of having to borrow another motor to get on the water in January! LOL

 

[tx1961whaler]

Re: Scored Cylinder: take to machine shop or D.I.Y?

Us boaters up here in the great white north dont want to hear about your "problems" of having to borrow another motor to get on the water in January! LOL

I thought everyone from Ontario was already down in Fla this time of year?

 

[RebeccaBurg]

Re: Scored Cylinder: take to machine shop or D.I.Y?

Wow- that really worked!!! Advice from you guys sent me in the right direction, finally got the parts after they lost my order, put it back together following the important bits in the service manual & now it's like having a new motor. Have to break it in like a new one. Need a reliable outboard because of my job (have to travel out on the water), so this really makes a difference!
Heh- I can understand the weather thing. Am originally from Wisconsin...boy do i miss the summer boating there. (Medical problems- can't do the cold anymore...oh darn, shucks)
anyways, thanks so much!!!!! Happy, happy. ... now am going to attempt to pry my "new" Johnson away from a friend who owns a dinky, small hp outboard and is suddenly enamored with the Johnson's power & speed. have to catch him first...