to overbore 1 cyl in john 112 spl

[66 joe]

How do you guys feel about overbore of 1 cyl? Marine shop advsd me to sleeve cyl 1 because other 3 bores are good and just need hone. I read in my manual that it is permissible to overbore 1 cyl .030 over. He claimed he didnt like doing that and recommended sleeving for about $ 200 more. THOUGHTS? thanks ,,,,,,,, Joe

 

[Faztbullet]

Re: to overbore 1 cyl in john 112 spl

It sounds as if he's trying to get another $200 dollars. You can bore up to.064 oversize and be ok as long as you rejet. All pistons no matter the oversize weigh the same that way you can you use STD. and oversize with no balance problems. I bore a max of .044 on these engines. I would see if .020 would clean it up then go .030 if it didnt. I would use a cast piston also and replace t-stats.

 

[bob johnson]

Re: to overbore 1 cyl in john 112 spl

fast seems like he has been there and done that...and knows what he is talking about....but he isnt in your shoes..

imagine the mechanic telling later on down the line telling you that you didnt take his advice and went with mis matched motor parts...and he isnt responsible for your NEW issues

the compression has to be different.

the next guy in line will be pulling his hair out when he finds the jest dont match and puts them all back to original... and has more issues

I think $200 isnt that much...and it gets you back to specs....so everything from then on is much easier to trouble shoot...PLUS the mechanic has to stand behind his plan of action and repairs.

of course if the job is $500 or more then that begins to get into another realm

bob

 

[jonesg]

Re: to overbore 1 cyl in john 112 spl

How do you guys feel about overbore of 1 cyl? Marine shop advsd me to sleeve cyl 1 because other 3 bores are good and just need hone. I read in my manual that it is permissible to overbore 1 cyl .030 over. He claimed he didnt like doing that and recommended sleeving for about $ 200 more. THOUGHTS? thanks ,,,,,,,, Joe

The manual is right.

The manual isn't concerned with what mechanics like doing.

 

[66 joe]

Re: to overbore 1 cyl in john 112 spl

to me $200 for sleeve wont break the bank. Im just concerned,,, is it good to sleeve these motors and it did seem like i'd have the mechanic 100% behind his work if we went that route. I mentioned my shop manual and I dont think he liked me telling him anything. He then said, I'll do whatever you want,, but I got the feeling he wouldnt stand behind it.

 

[jonesg]

Re: to overbore 1 cyl in john 112 spl

Some shops will not do one cylinder, they will only do complete $3K rebuilds.
That might have to do more with the guarentee they give than reality.

Either way you choose, I would want to see what guarentee they offer for their work.

Most of us here do all our own work except machining, thats why we're here.

 

[kenmyfam]

Re: to overbore 1 cyl in john 112 spl

If it was mine I would do any and all machining work in one trip to the machine. Although I do all my own machining it's the teardown and rebuild that is the pain. Depends on overall condition of the other bores as well.

 

[fixmyevinrude]

Re: to overbore 1 cyl in john 112 spl

How do you guys feel about overbore of 1 cyl? Marine shop advsd me to sleeve cyl 1 because other 3 bores are good and just need hone. I read in my manual that it is permissible to overbore 1 cyl .030 over. He claimed he didnt like doing that and recommended sleeving for about $ 200 more. THOUGHTS? thanks ,,,,,,,, Joe

You say that the "Marine Shop" advised you to ... My question is "Is the Marine Shop the shop doing the machining?" or are they sending it out and acting as a middle man. Most Marine Shops send there machining out. They don't do it in house because it is critical work that requires close toleraces with expensive machines by skilled techs and is not cost effective to do just a few engines a year. I would want to talk to the actual Machine Shop that is doing the job and if possible the machinist actually doing the work. You will want to use a shop that is familar with Outboard Marine Engine Machining.

 

[Faztbullet]

Re: to overbore 1 cyl in john 112 spl

I have never seen in a manual a max boring spec, have seen max bore spec for wear. I have a boring bar and bore all my customers blocks and hone to within .0005 of bore spec for cast pistons and add .001 for forged pistons Additional oversize will only add a little compression(3-5 psi) . A block rebuilt to .030 size may add 2-5 hp but nothing major. As jetting goes you can run a stock jet up to .020 and need to go up 1 size at .030. Most remanufactured powerheads for sale are bored .020 or .030 as these are the most common sizes.

 

[66 joe]

Re: to overbore 1 cyl in john 112 spl

He does send machine work out, and I asked him about sleeving and he claims to have done 5 just last year and never has trouble going that route.
I feel like Im gonna have to trust him in this case. I just like having as much knowledge as I can before paying for the work. Unfortanetly, time is not going to let me rebuild this motor. Was all ready to start breaking it down, but between work and kids and wanting it finished by summer, I know when to throw in the towel. I got good satisfaction out of removing power head and learned alot also. Joe