Any special handling for boring out 85 150hp?

Mik

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I'm working on rebuilding the powerhead on my brother's 85 Evinrude, 150hp. I've rebuilt a number of auto engines before, so it's not new to me.<br /><br />There are at least 3 cylinders that are bad (broken rings, somewhat scored) and I'll have to have them (probably all) bored out .020 or .030.<br /><br />Can a reputable machine shop bore and finish the cylinders or is there any special handling that needs to be done with these blocks?<br /><br />Mik
 

WillyBWright

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Re: Any special handling for boring out 85 150hp?

Nah, any machine shop that bores and hones can do it. All they'll need are the block, standard bore size, and what oversize pistons you'll be using. Some will want you to send the pistons so they can fit them. They need to go by the specs. The pistons fit far more loosely than 4-strokes. If they fit the bore to the piston, it'll be too tight.
 

Dhadley

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Re: Any special handling for boring out 85 150hp?

Well put Willy.<br /><br />Its real difficult to measure a cam ground, tapered and barrel shaped piston. Just get a shop that is know for boring outboards and you'll be fine.
 

rodbolt

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Re: Any special handling for boring out 85 150hp?

I have to disagree with willy on this one. most shops that dont work with two strokes much will mess it up. the ports need to be chamfered and deburred as well as the sleeves checked for signs of becoming loose in the casting.<br /> most of the piston to wall clearences are a bit smaller than a comparable 4 stroke. it will also make a difference on the piston type you chose. forged pistons need a looser wall clearence as well as a different cross hatch on honeing some of them. myself I UPS blocks to Rons marine in portsmouth VA. he has been a jonny/rude autherized machine/resleeving center for over 30 years.<br /> good luck and keep posting
 

Dhadley

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Re: Any special handling for boring out 85 150hp?

The newest forged pistons run the same finished bore size as the OE cast. <br /><br />A good machine shop that specialzes in outboard will know this. A finished bore size is all thats needed.
 

rodbolt

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Re: Any special handling for boring out 85 150hp?

thats what I say. use someone that is competent with the product. I have not had good luck using automotive machine shops to do Marine and especially outboard work. if the macine shop does it right it will work very well. good luck and keep posting
 

WillyBWright

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Re: Any special handling for boring out 85 150hp?

I definately understand what rodbolt is saying. I use a car parts/machine shop that sends the blocks out to another sister shop that does 2-stroke stuff too. I just send the block, a photocopy of the service manual page that shows the standard bore, and what oversize piston I'll be using. If you find a shop that has it engrained that the piston has to be fitted to the hole, then you're lost.
 

Mik

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Re: Any special handling for boring out 85 150hp?

Thanks guys, I'll make sure that I find a shop that does 2 stroke engines. I was aware that the ports need to be deburred, or it will break the rings.<br /><br />By the way, can I use cast pistons, or do I need to use forged? I'm sure that there's a big difference in price.<br /><br />Mik
 
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