Main bearing clearance--and piston clearance are they ok ?

[HAS]

I have more questions about my 1985 50HP. 4CYL.Mercury engine. What is the clearance between
the reed type main bearings and crankshaft?. The ridges on the crank are very small, when I rub a
finger on the crank I can`t feel them, I can feel them when I rub them with a fingernail. I cut two
pieces of .005" brass shim stock 1/4" wide x 1/2" long and put 1 under each main bearing, each
bearing locked to the crank two turns of a no.3 phillips screw driver before the screws were tight.
I hope that makes sense, are these main bearing units serviceable? Also bored cylinders .015" over
size all miked to 2.580", the new pistons miked to 2.575", lightly oiled the pistons fall in the cylinders
with a .003" feeler gauge and the pistons hold in the cylinders with a .004" feeler gauge. Is the piston
clearance ok? What about break in procedure?
I cannot overestimate the value of the help and the knowledge that I have received from the men on
this forum. .........THANKS TO ALL.......HAS

 

[Faztbullet]

Re: Main bearing clearance--and piston clearance are they ok ?

Your bore size is correct @ 2.580 and the 2.575 reading is correct for the skirt of piston. Your wall clearance is in spec as that is .002. The reed block internal grooves are labyrinth seal and the edges of the raised portions should have sharp edge to them. If they are battered,worn(copper colored) or edges knocked down replace them. They fit loose on crank as fuel charge makes the seal, if they are worn it will not idle well in gear as cylinders will "cross talk" thru passage and crankcase pressure will be low that operates fuel pumps. Remove them shims you installed, below in break in instructions....
http://mar-fab.com/BREAK-IN-PROCEDURE.pdf

 

[HAS]

Re: Main bearing clearance--and piston clearance are they ok ?

FAZTBULLET
MANY MANY THANKS this is good news, the raised part of the reed blocks are square
and sharp, even with 4 pistons and cylinder walls that were in very bad shape this engine
would idle very good for hours while running a crab line. I used the .005 shim like
plastigage just to see if that much would lock the reed blocks to the crank. I could not
turn them on the crank even before the screwes were hand tight. Uulike plastigage it
don`t give my the bearing clearance but it dose let me its close. THANKS AGAIN
..............HAS

 

[Faztbullet]

Re: Main bearing clearance--and piston clearance are they ok ?

Your welcome.... I'll PM you where to send my crabs!!!! ( just joking)