rebuilt motors

[workwear]

just wondering if rebuilding the top end would affect the bottom end...i was told that anytime you rebuild the top end of a motor.....the bottom end is soon to follow.....

[2 tone z71]

what kinda motor on a outboard you gotta split the cases anyhow and the crank bearings are individual except on smaller hp Yamahas there one piece like a snowmobile,ive rebuilt many and never had a problem ,if the crank is questionable have a machine shop look at it before you put it in back in,and im not a beliver in the new rings new pistons caused my bottom end to go thats ole wives tales

Edited April 7, 2008 by 2 Tone Z71

[boatman]

Not true. Your lower unit will be fine unless its already damaged.

[Bernie]

Boatman, I believe they were discussing the powerhead itself.

In a quality overhaul redoing pistons and rings the bearings in the crankshaft would be inspected anyway. Along with seals and other components.

It would be foolish not to.

What you may be referring to is overhauling a cylinder head on a 4 stroke as repairing the "top end"

In engines with lots of running time on them if you do a valve job it's possible that the "bottom end" may require repair soon as well.

Edited April 7, 2008 by Bernie

[jiggz]

rebuildng a powerhead wouldnt effect the lower unit, separate units! But when you do get the powerhead rebuilt, might as well get the impeller / seals checks (pressure tested) for your lower unit.

[Big Cliff]

Well, I usually only work on small engines but depending on the failure annalsys if the top end failure was caused by leaning out (piston and ring(s) scored or seized, I would sure be looking at the lower end seals, crank or crank case. Air leaks are the number one cause followed by running with improper carb settings or an air leak in the intake. Your question is a good one but hard to answer without knowing more about what caused the failure in the first place. Give me more information, what size motor, 2 or 4 stroke, symptoms pior to failure.