yamaha f50 bearings

[vaappu79]

how thick are 935cc yamaha's powerhead crankshaft and connecting rod bearings? there are 3 different bearings black, blue and brown.
also would like to know the thickness of the 995cc bearings as well.

[boscoe99]

Yamaha generally does not list bearing thicknesses. As you note, they simply go by colors.

The crankshaft will have some numbers on it and so too will the crank case. These numbers are compared to a chart within the Service Manual to determine the bearing color to be used in a specific crank case with a specific crank shaft. Connecting rods are done in more or less the same manner.

After the bearing color is selected, the crank shaft is installed into the crank case with the clearance being verified within specifications using plastigage.

What is the objective? Where are you trying to get to?

[vaappu79]

well i opened up my -96 mariner whitch has a same powerhead as yamaha and found a crankshaft that belongs to 2006 yamaha efi motor. the engine has run and only opened it because i had a lot of water in motor oil. and when i opened it i discovered that nro. 2 cylinder piston oil ring was damaged and there is a bad groove on cylinder wall. so i'm thinking of putting oversized pistons in there. did measure crancshaft and compared it to -96 crank and the difference is that the -06 crank has 0,01mm (0,0003937inch) smaller crank throws and even less difference on main bearings. however plastigauge gave oil clearance of 0,05mm (0,0019685inch) to 0,07mm (0,0027559inch) on current bearings. i have no clue what bearings there are now because i only found markins gc201 (if iremember correctly) and a logo whitch looks like lh on them. by the way nro.1 cylinder had a connecting rod of a newer efi motor as well whitch is about 35 grams (1.2oz) heavier then the others.

[vaappu79]

allright found bearing thickness on my repair manual. didn't look well enough before, but thanks anyway.

[boscoe99]

allright found bearing thickness on my repair manual. didn't look well enough before, but thanks anyway.

Interesting. Is it a Mercury/Mariner service manual that has the bearing thicknesses described

[vaappu79]

Yamaha mercury & mariner 1995-2004 repair manual. 762 pages. All motors 2.5 - 225 hp

[boscoe99]

OK. That is not a Yamaha service manual. Don't think it is a Mercury manual either. Maybe for a Yamaha/Mariner motor but produced by someone else.

[rodbolt17]

the merc F50 is different than the Yamaha F50.
the merc F40 and F25 on some models are the same as the Yamaha F40 and F25 other than paint color and 10 pin harness.
the merc/Yamaha marriage ended in a nasty divorce about 2003.

[vaappu79]

The powerheads of 935cc engines were same. Difference was in lower parts of the motor.

[rodbolt17]

yes in the 96 era the powerheads were Yamaha and the mid section and lower were merc designed.
however according to the interchange manual the cranks for the 05 and up EFI engines wont interchange with the 04 and older carbed motors.

unlike automobiles they don't offer undersize bearings for a reground crank.

lose a crank and its either weld it and grind it back down or scrap it.

crankpin and crank main journals are given as a nominal perfect figure.
the stamping on the crank indicates a deviation from nominal/perfect and that's how bearings are fitted by color.

its kinda like the F R and P markings on the gearcase,they indicate a deviation from perfect.