Machine Shop Advice

**wiigelec** · 10-16-2024, 11:07 AM

No local machine shops have the tooling for boring the blind cylinder holes in my Mercury 3.0L V6 two stroke block. So I can either send it off or provide the tooling. I'm not a machinist so I don't know specifically what is required, just that it costs around $2k. Maybe it's something that could be purchased used or rented?

One of the holes melted a piston so will need at least a good honing, maybe an oversize bore. The other holes could also use a good refresh on the cylinder wall surface. Haven't taken any measurements yet to determine if any boring is required.

Any machine shops worth shipping a fishing motor to? I'm in Wyoming if that makes any difference.

Thoughts? Thanks

**25two.stroke** · 10-16-2024, 11:23 AM

As I understand they have the tooling they are just afraid/unwilling to do it. At least the dozen shops around here are that way. They see ports in the cylinder walls and they get scared or hanging up their boring bar or whatever. Maybe Chris can chime in or Charlie...they both do that kind of work well but they are pretty backed up with work. I wish more of the local shops would be willing to do the basic cylinder work on 2 strokes.

**rock** · 10-16-2024, 02:00 PM

They make cutters capable of the loading forces a two stroke motor creates. The pressure release in the ports and the impact on the other side can be detrimental however I have bored hundreds with just the standard carbides. I think the main thing is the bottom of the bore. There are only .060 tween the bottom of the sleeve and the bottom of the bore so it can take a while to get your depth set correctly. I killed the first L3 I did. After that it's just cutting a hole which is what a boring machine does. The other issue is honing a blind bore as the hone cannot pass thru to make an even and consistent bore like you can on automotive stuff. JMO.

Rock

**wiigelec** · 10-18-2024, 08:41 AM

i’ll take measurements with a bore gauge and if within spec resurface the cylinder walls with a flex hone.

not sure about the aluminum transfer yet as i’m hesitant to use muriatic acid.

**rock** · 10-18-2024, 10:28 AM

Clean the cylinder walls before you try to hone or you will end up with funny shaped bores. Don't be afraid of muratic acid. If you can, use a rigid hone.

Rock

**6Killer** · 10-18-2024, 04:52 PM

2k is pretty steep. Boring blind holes is not difficult. Automotive shops are used to making large cuts .015 or larger per pass. Ports are not an issue with small cuts, .010 and smaller. Because you cannot "overstroke" the bore you have to get really close to the finished size before honing. Lots of small cuts result in a wall finish that requires minimal honing. (relatively speaking) Takes more time than an automotive block. Lots of Automotive shops are lazy and don't want to do what is required.

**skialot2** · 10-18-2024, 05:09 PM

Use a rigid stone hone. Not a flex hone. A rigid hone will pass over the ports and will show you highs and lows in the cylinder walls. A flex hone will fall into the ports instead of passing over them.

**wiigelec** · 10-18-2024, 07:33 PM

any recommendations on a hone?

**skialot2** · 10-18-2024, 08:09 PM

I used the one Harbor Freight sells. Even the cheap ones work good. Just make sure you use fresh stones.

4 in. Engine Cylinder Hone (harborfreight.com)

Good ones can get expensive.

Amazon.com: Lisle 15000 Engine Cylinder Hone : Automotive

**tlwjkw** · 10-18-2024, 10:42 PM

Originally Posted by 6Killer

2k is pretty steep. Boring blind holes is not difficult. Automotive shops are used to making large cuts .015 or larger per pass. Ports are not an issue with small cuts, .010 and smaller. Because you cannot "overstroke" the bore you have to get really close to the finished size before honing. Lots of small cuts result in a wall finish that requires minimal honing. (relatively speaking) Takes more time than an automotive block. Lots of Automotive shops are lazy and don't want to do what is required.

good ta see ya still around bud!!!

**skialot2** · 10-18-2024, 11:42 PM

I had 3 holes bored .015 in my 2.5 last year. $95 per hole for boring, honing and deburring. $45 per hole for honing and deburring only. But that is all they would do. They said they would punch it out for me but wanted no part of installing a sleeve or any kind of assembly.