opinions on what to do about scratches inside piston wall

apollothesun

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Re: opinions on what to do about scratches inside piston wall

hey Jayrock,
where did you buy the ball hone for the exhaust cylinders at?
 

apollothesun

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Re: opinions on what to do about scratches inside piston wall

i need help in finding a piston that will work to replace piston 4. im probably gonna need to bring in the new piston to the machine shop so they can measure properly. which wiseco piston would work? or do i just say cut it to .040?
 

wilde1j

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Re: opinions on what to do about scratches inside piston wall

Unless you have the tools and skills to properly measure the bores, let the machine shop tell you the OS to get. Just tell them you will use brand "x" pistons. Once they measure, they should recommend the smallest OS that will allow proper bore cleanup.

Bearings are readily available.

If you don't have one, now would be a good time to get an OEM shop manual.
 

Jayrock

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Re: opinions on what to do about scratches inside piston wall

hey Jayrock,
where did you buy the ball hone for the exhaust cylinders at?

I used to use a Carbide Ball shaped deburring bit, Carbide cone deburring bits work good too, but they are spendy. So, Its not exactly a Ball hone that I use now. I use a cone shaped sanding bit that Dremel Makes. I paid less that 10 bux for the one I have now, and I have used it several times.
 

Jayrock

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Re: opinions on what to do about scratches inside piston wall

hey Jayrock,
after reading your post you enlightened me to break the powerhead down completely.
im glad i did too, piston 1 and 2 rings were broken also, probably from debri from
piston 4. upon looking and feeling around at the piston 4 wall, im gonna have to rebore to a bigger piston. the scratches on the wall can be felt with my finger nail. all the other piston walls are good just need some honing to do.
alot of carbon gunk inside the exhaust housing that i proceeded to clean. theres a machine shop that works on marine motors closeby. i will bring the powerhead to them and have them examine the piston wall.
one bummer is i cant find one of those small roller bearing. i searched everywhere for it. im hoping i can still buy those still.

Once you have an idea what everything will cost, STOP before proceeding. Now, look into what a used crankcase costs, that has never been bored, or has all the machine work already done. Might be less expensive to just replace the crankcase... Food for thought.
 

apollothesun

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Re: opinions on what to do about scratches inside piston wall

Unless you have the tools and skills to properly measure the bores, let the machine shop tell you the OS to get. Just tell them you will use brand "x" pistons. Once they measure, they should recommend the smallest OS that will allow proper bore cleanup.

Bearings are readily available.

If you don't have one, now would be a good time to get an OEM shop manual.

thanks jim for the valuable information about piston sizing, i would of never of thought that.
i hear ya jim, if i didnt have the oem manual, i would be stripping bolts off the motor and would be still on the lower unit.
 

apollothesun

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Re: opinions on what to do about scratches inside piston wall

I used to use a Carbide Ball shaped deburring bit, Carbide cone deburring bits work good too, but they are spendy. So, Its not exactly a Ball hone that I use now. I use a cone shaped sanding bit that Dremel Makes. I paid less that 10 bux for the one I have now, and I have used it several times.

fantastic idea, now i have a reason to use that sanding bit!
 

apollothesun

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Re: opinions on what to do about scratches inside piston wall

Jayrock, i like how you think. toast to you bro. if i was close down to diego i would definately buy you a drink. i will try the local craigslist, no sense in spending more cash than i have too and i can spend more time with the family. :)
i went by to that local machine shop and they only do cars.
anybody tried sending their powerheads out to get them rebored and pistoned up? any good shops out there that do this?
 

bob johnson

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Re: opinions on what to do about scratches inside piston wall

I stripped my block which only had one out of round piston. but the bore was right at max spec, and you always need to hone to get the rings to seat...so I went .020 over size on all cylinders...because for all the work I am doing , I dont want it to bite me in the behind, because i tried to save $200 someplace..

I sent my block to Lashelle Engine Restorations( freeport lll). I actually got the number from a palce that didnt really want to do my block, and mention that he sends all his blocks out...so i asked who.. this was the guy.. It came back really nice( i have the measuring equipment and tools to know!!) I am thinking that a bore and hone was about $40 per hole...

but you can ask him... he had already done hundreds of 60 degree blocks like mine...which are a little tricky with that flat bottom bore!! need special hones to do blocks like these.


good luck

bob
 

snowseeker

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Re: opinions on what to do about scratches inside piston wall

I rebuilt my own 60hp this last summer. The only tool I don't have is the mill for boring so I had a local machine shop do that work. Once I got it back I brought the cylinders up to size with the hones. Then debured all the ports, debured the pistons, cleaned everything up and assembled. I have ran 3 tanks of gas threw the motor already and everything is working great! The pistons are .020 over. We got the motor in to be a parts motor for our 70hp on the work boat but the only parts we ever needed off this motor was the trim relays. lol

We got this 60 without a head and all 3 pistons and cylinders were scored from heat. It was a very fun build and I think I have $300 total in the motor with new pistons, head, and complete gasket set.

I just posted a couple pics here: http://forums.iboats.com/showthread.php?t=97206
 

DargelJohn

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Re: opinions on what to do about scratches inside piston wall

Off subject a little... But I have been recently told by a professional engine builder and a manufacuturing rep for an aftermarket piston kit company, that as long as the machine shop does their job properly, you do not have to worry about piston or ring end gap clearances. Pistons and rings are built to very exacting tolerances these days.

For Example: Let's say your Standard Bore Size is 3.500" and you want to bore it out to 3.530" (.030 oversized). As long as the machine shop bores the cylinders to that spec, the .030 piston kits will work.

My engine rebuild turned out perfect, without supplying the piston kit to the machine shop. I was also advised to use cast piston and not forged. Forged are made of harder metal and can damage the cylinders more during a failure.

Just my expierence.
 

bob johnson

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Re: opinions on what to do about scratches inside piston wall

I rebuilt my own 60hp this last summer. The only tool I don't have is the mill for boring so I had a local machine shop do that work. Once I got it back I brought the cylinders up to size with the hones. Then debured all the ports, debured the pistons, cleaned everything up and assembled. I have ran 3 tanks of gas threw the motor already and everything is working great! The pistons are .020 over. We got the motor in to be a parts motor for our 70hp on the work boat but the only parts we ever needed off this motor was the trim relays. lol

We got this 60 without a head and all 3 pistons and cylinders were scored from heat. It was a very fun build and I think I have $300 total in the motor with new pistons, head, and complete gasket set.

I just posted a couple pics here: http://forums.iboats.com/showthread.php?t=97206

you got THREE NEW pistons and a NEW HEAD and a gasket kit for $300!!!!!!!!!!!

Id love to know where you buy your parts....I think my pistons were $100 each....even on ebay they are $80+

bob
 

wilde1j

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Re: opinions on what to do about scratches inside piston wall

Jayrock, i like how you think. toast to you bro. if i was close down to diego i would definately buy you a drink. i will try the local craigslist, no sense in spending more cash than i have too and i can spend more time with the family. :)
i went by to that local machine shop and they only do cars.
anybody tried sending their powerheads out to get them rebored and pistoned up? any good shops out there that do this?

Marine Machine shops:
Mar Fab -- talk to Kurt or Dan at 931-738-2815 (Tennessee)

Flagship

Tribble

Blackburn

Roehrs

Riverside

You might also consider buying a rebuilt powerhead (iboats has them). They typically come with a warranty as well. I would strongly recommend against anything but a marine machine shop. The others don't have the experience or the fixtures to do it right. The good shops are up on service bulletins and fixes to give you a long lasting job.
 

apollothesun

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Re: opinions on what to do about scratches inside piston wall

thanks Bob, Jim, Snowseeker and Dargeljohn for the treasure trove of information.
i was up late last night hunting for a engine in hopes for a replacement.
i got a reply about an 85hp 1976 that can replace my existing motor which i can sell my motor for parts. he's asking $650, 120psi on all cylinders, new water pump recently serviced. sounds like a good deal. although my wife has to hear about the cost cuz my allowance cant afford paying for that right now.
i called around this morning for shops that do reboring and all 3 say they send them to one place up north. i called the shop and talked to dale and was very helpful and eager to help me. he said he can do $50 a bore and readily has pistons availble for replacement. i feel confident about this transaction.
so, what do you guys think,
if i can get the boring done for 50, 150 for piston and rings, 50 bucks for another set of rings for the other pistons, powerhead gasket set 100, maybe two weekends to put it all together totaling about 350.
or go with the 85hp, less horsepower, double the cost, although more time with the family
gonna have to weigh on the thoughts till the end of the day.
 

snowseeker

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Re: opinions on what to do about scratches inside piston wall

you got THREE NEW pistons and a NEW HEAD and a gasket kit for $300!!!!!!!!!!!

Id love to know where you buy your parts....I think my pistons were $100 each....even on ebay they are $80+

bob


Everything was from ebay. I may have stretched the total a bit but it for sure was not over $400. I believe the pistons were $50 each with rings and pins, gasket set was $55, head was $65, and thermostat and cover were $25. The head was not new.
 

Faztbullet

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Re: opinions on what to do about scratches inside piston wall

you got THREE NEW pistons and a NEW HEAD and a gasket kit for $300!!!!!!!!!!!

Id love to know where you buy your parts....I think my pistons were $100 each....even on ebay they are $80+

bob
Now Bob.... I thought I gave you a heck of a deal on your parts even the new S/S mounting bolts.;) You still need a rectifier/reg???:confused:
 

apollothesun

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Re: opinions on what to do about scratches inside piston wall

well i dropped the block off this weekend and got a reply back from the machinist today.
he says that piston 4 needs to be bored to .040
that size because the ports already at .030
the other ports are okay but recommends piston 3 be rebored too
he says if he cant bore .040 then he wont charge me, and suggests a resleeve which is about 220.

looking closer at the pistons over the weekend looks like piston 2 and 3 need to be replaced. some scratches that can be felt with the finger nail.
what happens to the scratches? does it overheat the piston walls? can the scratches be smoothed down with a dremmel and sanding bits? or is that asking for trouble

if i do rebore all the ports,
thats about 100 per piston plus 50 per bore totalling about 600 not including rings.
man, i dont think its worth it.
the boat is a 1977 apollo ski boat. the boats in decent shape and so is the trailer.
what kind of resale would i get if i do a complete rebuild on the motor?

what if i go ahead on the rebore on piston number 4, find used pistons for 2 and 3 and put it all back together. how long do you think its gonna last?

wouldnt it be cheaper to resleeve all the ports and get pistons for them?

last option would be to part it all out and use the funds for a new motor.
 

bob johnson

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Re: opinions on what to do about scratches inside piston wall

Now Bob.... I thought I gave you a heck of a deal on your parts even the new S/S mounting bolts.;) You still need a rectifier/reg???:confused:

no doubt at that moment in time you were king!!!.. and since you cherish that so much, the next time i need new pistons and a NEW HEAD and gaskets lets remember this conversation and ill send a check for $301!!!!!!! ha ha ha

wait... I dont want a next time!!!!!!!!!! ha ha ha

I am going to need another rectifier-reg for sure...but I wont need it till summer i guess.. I might need a few more things as well...

things picking up in your place yet????? got to be some stirring of the fishermen down your way by now!

bob
 

apollothesun

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Re: opinions on what to do about scratches inside piston wall

got off the phone with the machinist this morning and had to bore cylinders 3 and 4 to
.040
i asked to see if i can get away with piston 1 and 2 for a while but he said im gonna need new piston heads.
so, im looking for some pistons 2 X .040 and 2 X .030
wiseco pistons were coming at 100.00+ but includes wrist pins and bearings
trying to find a pair of good .030 pistons

hey bob, i see you were in my shoes sometime last year,
http://forums.iboats.com/showthread.php?t=373454&page=2
how did you fare with that 80hp motor? any parts for sale?
 

Jayrock

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Re: opinions on what to do about scratches inside piston wall

got off the phone with the machinist this morning and had to bore cylinders 3 and 4 to
.040
i asked to see if i can get away with piston 1 and 2 for a while but he said im gonna need new piston heads.
so, im looking for some pistons 2 X .040 and 2 X .030
wiseco pistons were coming at 100.00+ but includes wrist pins and bearings
trying to find a pair of good .030 pistons

hey bob, i see you were in my shoes sometime last year,
http://forums.iboats.com/showthread.php?t=373454&page=2
how did you fare with that 80hp motor? any parts for sale?

You will probably have to stick with Wiseco bro. It is not wise to use pistons of different makes in the same engine. They might not weigh the same. I am surprised the machinist did not mention this too you.
 
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