To continue with rebuild???

[66 joe]

Ive got a blown upper starboard piston in a Johnson 112spl. Attempting to pull power head off and take to machine shop to check bore and heads. I have shop manual and if all passes I'd like to install new piston/rings and hone cylinder. All 4 cylinders look extremely clean with very visible crosshatch all around. I think cause was from lack of maint since motor prob has less than 100 hrs. Now while removing nuts/ bolts on power head, Ive sheared about 3 of them in half. I think with heat and vice grips Ill be able to get them off, Just makes me wonder if Im tackling too big of a project. Or should I just give power head to a shop and let them rebuild.

Thanks ahead for replies,, Joe:redface:

 

[tashasdaddy]

Re: To continue with rebuild???

it is worth rebuild, you are this far into it why quit.

 

[emdsapmgr]

Re: To continue with rebuild???

If you are somewhat mechanically inclined and have a factory manual, why not tackle it yourself?

 

[Sandhammaren05]

Re: To continue with rebuild???

What do you mean by a blown piston, what damage?

Ive got a blown upper starboard piston in a Johnson 112spl. Attempting to pull power head off and take to machine shop to check bore and heads. I have shop manual and if all passes I'd like to install new piston/rings and hone cylinder. All 4 cylinders look extremely clean with very visible crosshatch all around. I think cause was from lack of maint since motor prob has less than 100 hrs. Now while removing nuts/ bolts on power head, Ive sheared about 3 of them in half. I think with heat and vice grips Ill be able to get them off, Just makes me wonder if Im tackling too big of a project. Or should I just give power head to a shop and let them rebuild.

Thanks ahead for replies,, Joe:redface:

 

[66 joe]

Re: To continue with rebuild???

out fishing 1 day, and motor started running rough. I thought, oh some bad gas, kept going. then power became weak. Compression test at home revealed 10-15 lbs on upper starboard cyl. All other test ok (within 10% of eachother) Ok pulled starboard head, only to find bout 1 inch chuck of piston between top and ring grove broke off. It beat up cylinder head (which ive replaced) and piston,, but bore is perfectly clean (to my eye) Ive rebuilt a 389 pontiac and have alot of tools. Shops have told me, you have to re-bore all cylinder or get powerhead. You cant fix 1 cylinder. Well my manual says you can over-bore one, and I think I can get away with a hone.
I'd be happy to get 2 more seasons out of motor, thanks,,, Joe

 

[jonesg]

Re: To continue with rebuild???

The shops are just talking about their guarentee, they will not issue a guarentee unless they get you for $2k+.
Theres places like that here, they won't rebuild without painting it too.

But you can take it to a machine shop and have done what you want doing.

 

[66 joe]

Re: To continue with rebuild???

Next question is, do I have to take the remaining 3 pistons out, or can I just focus on damaged one? Ill have maching shop check for out of roundness and cyl taper, also make sure heads arent warped.

 

[Dhadley]

Re: To continue with rebuild???

You need to get it all apart. Once you measure it I think you'll find the other 3 are either right on the edge of being out of spec (round) or are out of spec regardless of what they look like. If you get real lucky and they are within spec after honing and the pistons are't worn, you can re-ring the other 3.

 

[splitshot]

Re: To continue with rebuild???

dont forget to look at the dowels in the ring grooves if they are starting to push in replace them all

 

[Mas]

Re: To continue with rebuild???

I would be concerned with why the piston blew in the first place. You don't want to do it twice...right? Did your autopsy shed any light as to why it blew?

MAS

 

[66 joe]

Re: To continue with rebuild???

I agree with you 100%. I'm thinking over-heat, coking?, lean carb condition.
What I do know is the temp alarm wasnt functioning correctly. (been corrected) Alot of wiring has corrosion/electrolosis and I need to clean all contacts. Like my fuel primer wasnt working for a long time and it would always take me forever to cold start motor. Then I found depressing key wasnt priming motor all because corrosion inside plug next to primer.
I do know when piston blew,, I was idling motor alot, next to high current fishing ground or when I fired it up on driveway day before, motor was shaking alot,,,, thought that was bad gas, but motor ran good for 10 miles out to fishing ground. I will have both carbs rebuilt upon completion

 

[emdsapmgr]

Re: To continue with rebuild???

When you rebuild the carbs, I'd have a serious look at the jets in side of the carb that feeds the low compression cylinder. You may find debris clogging the high speed jet. Also, check the rubber water diverters in the powerhead to make sure they are still intact.

 

[66 joe]

Re: To continue with rebuild???

water diverters are in place; carb condition is still unknown; now I'm having trouble seperating power head from lower unit. I guess thats what weekends and a six pack are for. to be continued

 

[Sandhammaren05]

Re: To continue with rebuild???

Well, you know that the cyl. must be honed, at the very least. You can go .002" over with a hone, if you need more than it must be rebored. Naturally, you can repair one cylinder, you can bore it .020" over!

out fishing 1 day, and motor started running rough. I thought, oh some bad gas, kept going. then power became weak. Compression test at home revealed 10-15 lbs on upper starboard cyl. All other test ok (within 10% of eachother) Ok pulled starboard head, only to find bout 1 inch chuck of piston between top and ring grove broke off. It beat up cylinder head (which ive replaced) and piston,, but bore is perfectly clean (to my eye) Ive rebuilt a 389 pontiac and have alot of tools. Shops have told me, you have to re-bore all cylinder or get powerhead. You cant fix 1 cylinder. Well my manual says you can over-bore one, and I think I can get away with a hone.
I'd be happy to get 2 more seasons out of motor, thanks,,, Joe

 

[Sandhammaren05]

Re: To continue with rebuild???

Were it my motor I'd replace rings and rod bearings in all cylinders, plus crank seals and o-rings, and run the motor another 10 years. I have no idea what a rebuild costs today. 25 years ago I charged $500-700 labor to rebuild 3 cyl. and V-6 racing powerheads in my garage. Parts for a 2 cyl. rebuild run over #200.

Well, you know that the cyl. must be honed, at the very least. You can go .002" over with a ball hone, if you need more than it must be rebored. Naturally, you can repair one cylinder, you can bore it .020" over!

 

[Faztbullet]

Re: To continue with rebuild???

A ball hone is used to break glaze or put a finishing cross hatch in cylinder. You cannot hone a cylinder oversize with a ball hone, use a ridgid hone to clean and true, ball hone to finish.

 

[Sandhammaren05]

Re: To continue with rebuild???

You can only use a ball hone on a looper, and it's too easy to cut away .002"! I ball honed away nearly .002" inadvertently on a cross flow OMC 35 block recently.

A ball hone is used to break glaze or put a finishing cross hatch in cylinder. You cannot hone a cylinder oversize with a ball hone, use a ridgid hone to clean and true, ball hone to finish.

 

[66 joe]

Re: To continue with rebuild???

my boat mechanic has took over most of the job from me; I took him power head and he showed me some ridges in the cylinder that i didnt see, so off to the machine shop the block went; 2 cylinders looked like trouble; He claims shop will prob want to over bore all 4 cylinders .030 over. Labor isnt gonna break my bank; he quoted $750 for labor and assembly of power head. ( not including parts ) of course I have to pick up power head and re-install it. Ill rebuild carbs. And take boat back to him for initial fire up. More to come, hopefully b/4 summer,,, Joe

 

[Faztbullet]

Re: To continue with rebuild???

You can use ball hone in any engine as long as you have proper size. Thats why I have about 10 of these. A ball hone may remove that much if you stay at it a while or wrong size hone for cylinder but either way cylinder will not be round. The proper way is to hone cylinder with a rigid hone (sunnen) to clean up cylinder for measurements. It will also leave dark spots on liner where stones did not contact liners, these are the worn areas due side thrust on piston. A ball hone will not show you this and if over .003 out it needs borining anyway.

 

[Sandhammaren05]

Re: To continue with rebuild???

As one who raced Allisons for 11 years, I'd highly recommend that you switch the 75 to the 13' Allison and the 150 to the 15' Allison. Darris or Paul will give you the same advice.

You can use ball hone in any engine as long as you have proper size. Thats why I have about 10 of these. A ball hone may remove that much if you stay at it a while or wrong size hone for cylinder but either way cylinder will not be round. The proper way is to hone cylinder with a rigid hone (sunnen) to clean up cylinder for measurements. It will also leave dark spots on liner where stones did not contact liners, these are the worn areas due side thrust on piston. A ball hone will not show you this and if over .003 out it needs borining anyway.