Honing/Boring

[paulwjax]

I have a 1974 115hp Johnson that has light scoring in the cylinders and was wondering if I should do the honing/boring work or have it sent to a machinist.
Also, if I were to do the work I saw Flexhones in a bunch of different grits. Which one do I use or are there multiple grits to use?

 

[wilde1j]

Re: Honing/Boring

If you can't tell whether it needs honing or boring, I would suggest you have a marine machine shop bore the block (it's not a DYI deal) and install the smallest oversize pistons and rings. Let the machine shop tell you the oversize needed and make sure to tell the piston you'll use.

BTW, Mar-Fab is a good shop.

 

[paulwjax]

Re: Honing/Boring

Anyone know a good machinist in Jacksonville FL?

 

[bashr52]

Re: Honing/Boring

Light scoring can be honed out, deep gouges need to be bored. I have both a straight honer and a ball hone. I love the ball hone, it leaves nice cross hatching on the cylinder walls. You can do the same with a straight hone, if you are good with it and know what you are doing. I agree though, if there is any doubt as to what it needs, take it somewhere to get checked out.

 

[wilde1j]

Re: Honing/Boring

You need to start by using an inside micrometer in the bores and also check for roundness of holes. If within specs, honing may work, but I doubt it for a 35 year old motor. BTW, what was compression all around?

 

[Dhadley]

Re: Honing/Boring

Second that. If you don't have access to a dial bore gauge then let a outboard machine shop (not automotive machine shop) measure it and make a recomendation based on size.

If you have a piston that needs replacing, go to the first oversize and bore that cylinder.

Don't mess around with a shop you are not 100% positive about. Mar-Fab is at least 100%. So is Flagship in Punta Gorda, just in case you want to use someone in Fla.

 

[paulwjax]

Re: Honing/Boring

I'm not sure what compression was since the motor wasn't running when I got it. (Free motor) The pistons were stuck in it but any rust in the cylinders has come off with wd40 and 0000 gauge steel wool. It was sort of a "ran when parked" deal so I just decided to rebuild the thing from the ground up instead of trying to put bandaids on little problems.

 

[paulwjax]

Re: Honing/Boring

You need to start by using an inside micrometer in the bores and also check for roundness of holes. If within specs, honing may work, but I doubt it for a 35 year old motor. BTW, what was compression all around?

I'll have inside measurements soon. Northern Tool was out of micrometers that read to thousandths when I went in.

 

[kenmyfam]

Re: Honing/Boring

Without a doubt you need to check the bore dimensions. How bad is it ????

 

[paulwjax]

Re: Honing/Boring

It's not great but I've seen worse. Also, with 0000 gauge steel wool the rust goes away.
I've attached 2 pics of the cylinders. The first is what it looks like after I steel wool the inside and the 2nd is the worst cylinder on the powerhead. None of the cylinders have grooves in the lip.

 

[kenmyfam]

Re: Honing/Boring

Check with the bore indicator and compare to original spec's

 

[Faztbullet]

Re: Honing/Boring

From the looks of cylinders, I myself would go ahead and bore due to the rust issues, if its rusty it is pitted. A few pitts here and there wont hurt anything but from looks it is 360 around ports. Also make sure of year model as there is a BIG difference in a 1973 & a 1974 piston(wrist pin height).

 

[paulwjax]

Re: Honing/Boring

I've found a shop in town that does boring for about $20 a hole that a few people have used with decent results. I'm going to go for the smallest overbore possible.

It's definitely a 74. The silver tab on the powerhead says 115esl74b but I still went to check just in case.

 

[Dhadley]

Re: Honing/Boring

Be very careful. Ask the shop what they use for the finished bore size. Let us know what they say.