Getting ready to build a 260

[bc's xtb21]

I'm getting ready to build a 2.5 260, it will be my first outboard to build. I have got it tore down and everything looks good, but I have heard different people talking about needing to check the cylinders to make sure they have not wore egg shaped. I was just wondering what kind of tolerance am I looking for on this motor, or variance from it. Also I need to buy a dial bore gauge, I guess I am calling it by the right name, just wondering best place to buy one. Thanks for any info

 

[David Lanham]

Your PM box is full:


I have a used Starrett inside micrometer set i'm willing to sell cheap, $45 shipped. I need to double check to make sure it can measure up to ID's you need, 3.5 inches and higher. I can also check the accuracy using a digital calipers I have. I'll let you know this evening.

 

[David Lanham]

The ID micrometer set set I have is made by Lufkin. It has adpater bars to measure IDs up to six inches. The micrometer adjustemt has 1/2 inch travel with 0.001 tick marks.

I cheched the adapter bar accuracy for the 3.5 inch ID using my analog and digital calipers and it was dead on. I also accuracy checked my calipers using a 3.0 inch ref gage as well.

 

[bc's xtb21]

Thanks David, got my pm box cleared out. You gotta pm

 

[suicidealli]

1/2 thous. Or .0005 is perfect as I have seen. .001 is pretty good. .002 need to be straighten IMO. Ruck will have them within .0005, or 1/2 thous.
Also measure the pistons too. Make sure they are round. At the skirt if they measure 3.392 I won't use them in a hippo motor. 3.393 is questionable. 3.394, and round rock on.
If they piston are lighten, balanced, top pined' round just a touch small. I will have them recoated. If the block needs to be nicked I have ruck make the bores .001 smaller, and use the wore, but round piston, you just have to file the ring ends to make sure your ring gap is correct. .001 x pi that means you over all ring is a little over. .003 bigger than it needs to be.

On the next rebuild you can hone it heavy back to. 3.500, and put new pistons in it. Makes for 2 great builds.

 

[bc's xtb21]

Thanks as always Roy, for the info. That's one thing I've been confused on, I've heard folks say to check for roundness of the bore and pistons, and I didn't know if there is any acceptable tolerance for being out of round or do they have to be perfect? Also, do you think I need a factory manual for this build? Will it have all the tolerances and info I need? I would feel better about giving a merc dealer a hundred bucks fora book if I knew it was worth it. Thanks again!

 

[suicidealli]

The book is a great tool... Not sure about merc tolerances tho....lol I wouldn't go by what they say about bores, etc... Torq specs are in there, how to tear it down, Assemble, etc.
Testing electrical components. Get the book!!!!! IMO

Look on eBay for the book. Sometimes they are on there.

Any questions call me

Roy

 

[bc's xtb21]

I'll get me a book. I'm still at the low end of the learning curve on this stuff.lol