Mercury 115hp Rebuild - Bearing Play

[bigjig]

I am rebuilding a 115 hp merc (2001 model, 4 cyl inline) and I'm a bit concerned as to the amount of play in the big end bearings. Crankshaft was lightly cleaned and bearings are new. Does anyone know of specs for the minimum permissible diameter of big end bearing journals / max diameter of con rod internal or perhaps has access to original Mercury (new) parts and could run a mic over them for me please?

[macka17]

I am rebuilding a 115 hp merc (2001 model, 4 cyl inline) and I'm a bit concerned as to the amount of play in the big end bearings. Crankshaft was lightly cleaned and bearings are new. Does anyone know of specs for the minimum permissible diameter of big end bearing journals / max diameter of con rod internal or perhaps has access to original Mercury (new) parts and could run a mic over them for me please?

Ring Merc. Workshop and ask for Min oversize. and Dia of journals. Maybe Google on net?

If sloppy. get shaft ground down to first. O/S. Fit new bearings. THAT size. and go for it.

You put it back together sloppy. You're asking for it to bind when running somewhere 20 miles offshore.

That is one thing you don't take risks with... it could be your life.

Macka17

[bigjig]

Thanks Macka17

I rang Mercury last week and no specs from them. Same with a Clymer manual. Waiting for a genuine merc manual to arrive later this week which might have specs.

Also spent most of yesterday evening googling, but found nothing.

I wasn't aware that these cranks could be ground down? Do you have any info on that and where to source the bearings?

Does anyone have any experience with rebuilding shafts? I gather there is a couple of companies that do it, although results are somewhat inconsistent I hear. There is a company here in Newcastle that laser welds shafts, although I don't know if that would be successful for hard face shaft?

[IWANNABROCK]

You can get crank shafts resized, but make sure you use a reputable company as they need to be done properly or the shaft can be weakened and snap if not re-hardened properly.

[a boat]

Hi Bigjig, wlecome to fishraider. Be very careful who you use if you choose to re surface the Crankshaft. It is not that easy and we have had mixed success. You will not find a measurement for what you are after and if the Big end journal on the crank has no pity marks or discolouration than use a new bearing and torque the conrod to the correct setting and you will be fine. If you are not confident bring it by one day and I can have a look at the crank and rod and see what I think.

Cheers,

Huey.

[macka17]

Hi

Spoke to My Opti Supplier today. Also the best O/B mehanic round here.

He said. on the 2 strokes. The bearings are roller. they are loose. just clean up shaft. so the cage will bind. and reinstall after wiping with oil. 4 str. Diferent.

Regards

Macka17

[bigjig]

Update -

Have finished rebuild and outboard seems to run fine.

For reference to anyone else doing a similar rebuild, here are the dimensions as measured for crank journal outer diameter and conrod big end inner diameters. In inches. These are NOT factory measurements, just what I rebuild mine at, but should give you a ballpark figure to compare yours against.

Piston 1 is top. Crank OD measured at two points 90 degrees apart for out of round.

Piston # - crank OD - BigEnd ID

1 - 1.415/1.416 - 1.737

2 - 1.415/1.416 - 1.738

3 - 1.416/1.417 - 1.736

4 - 1.414/1.415 - 1.735

Hope this is of help to someone else. Thanks to all those who took the time to reply to me.