Engine balancing

[merc1250bayliner]

I have a early 90s 175 mercury 2.5 block. I have no rotating assembly for it. I am wondering, can I just buy a crank and rods/pistons separately and put it together? Or does the rotating assembly need to be balanced like a car engine?

[Capt.Insane-o]

If you ever component weighed just about any outboard regardless of brand, the answer is no. "production tolerance" is a pretty broad spectrum.

[powerabout]

Manufacturers swap rod and piston styles/weights around with same crank so we know its not a problem. Both OMC and Merc
You can make sure all rods ( each end) and pistons are the same weight in an engine though

[David - WI]

Balancing isn't an issue at "normal" rpm's but you do have to choose a crank that fits your block... rods that fit your crank... and pistons that fit your rods.
(Not all 2.5L cranks fit all 2.5L blocks).

http://www.biggerhammer.net/mercury/

[Chaz]

I have a early 90s 175 mercury 2.5 block. I have no rotating assembly for it. I am wondering, can I just buy a crank and rods/pistons separately and put it together? Or does the rotating assembly need to be balanced like a car engine?

That all depends on if your an engine builder .. or if you just throw factory junk together.

One runs smooth as silk .. the other shakes like an old Maytag washer.

The choice is your's .. ;)


https://www.hinesindustries.com/images/pdf/reciprocalmass.pdf

[Forkin' Crazy]

That is a lot of trouble??? Why not buy another motor and just rob the parts off it if the block is that good???

Chaz.....


https://www.youtube.com/watch?v=dq6T5BojXc8

[Chaz]

Factory balance is an exercise in how crappy you can make parts .. and still have the motor run .. ;) :D

Forkin, Thats a fine azz Maytag ya got there .. :cheers: