Semi weight matching??

**Old BASS Ranger** · 11-20-2017, 03:21 PM

Hey folks recently joined and my first post.

Working on my first outboard rebuild. It's a 95' 2.5l 200hp XRi. Going to be used for a fishing engine so no extreme rpms.

The block is bored 30 and I have Pro Marine components from my machinist. I have been through the posts on weight matching and balancing. Some of which I understand some I don't and most isn't relavent to my build anyways. However I still find it interesting and want my engine as smooth and durable as possible. I'm not planning on doing a full weight matching by grinding rods and pistons but was wondering if you smart guys can tell me if it's better to put like weight assemblies (piston pin and rod) across from each other or not. I have them grouped in pairs that are close. (Within a gram to gram and a half). But there is as much as 7 grams between the pairs. What's your thinking on this?

**CircleHook** · 11-21-2017, 06:54 AM

It came from factory with those components - put it together and run it-

**Old BASS Ranger** · 11-21-2017, 09:49 AM

First off thanks for the reply.

Well actually it didn't come with those parts. The pistons are all new and I see quite a bit of difference in the weight among the set. I haven't cleaned up an old piston to compare it to. I was trying to even it out with the difference in the rods as well. Am I just being foolish? Maybe I should ask how much is too much imbalane between components for future reference?

I ask because I'm going to be doing more engines one of them will be more performance based.

When I have put my mud drag motors together ( big block Mopar) my crank grinder did balancing for me because I was doing offset grinds different rod length and such. But with these outboards I'm in charge of deciding what's "good enough" so I need a bit more education I think.

**eli** · 11-24-2017, 11:28 PM

its your motor if you want to make it nice go do it weight match all of it then you will know what a good motor it is case you sell it the buyer will like , most low rpm motors wont know the difference if its not matched i have assembled many motors with 15 and 30 over bore same block not weight match they run fine 5500 rpm if your going to turn 5500 to 7500 then by all means match weight .

**HStream1** · 11-25-2017, 06:07 AM

If you are not going to go full blown and weight match (Blueprint the Pistons and rods). Weigh the Three Port and three Starboard. match as closely as possible in pairs. 1&2, 3&4 5&6.

**Steve Pope** · 11-25-2017, 05:42 PM

There is a real clever guy on this site, goes under the name of TRex. He put together a merc with a mix of diferent style rods and pistons, just to see how it would run. He said you could not tell any difference from a motor with matching parts.Steve

**Krazymaan** · 11-25-2017, 09:33 PM

If your going to do a more performance motor later on. This is the time to practice. you really only need a gram scale. and sanding type tools. But if you weigh the rods, make sure you have a stationary peg to hang the rod off of and the other side on the scale and weigh each end to the same weight, not just the whole thing. Easy stuff. Youtube it.
You can go all the way to this extreme if you want too.
Even the piston has been channeled

**Captain75** · 12-01-2017, 10:57 AM

Originally Posted by Krazymaan

If your going to do a more performance motor later on. This is the time to practice. you really only need a gram scale. and sanding type tools. But if you weigh the rods, make sure you have a stationary peg to hang the rod off of and the other side on the scale and weigh each end to the same weight, not just the whole thing. Easy stuff. Youtube it.
You can go all the way to this extreme if you want too.
Even the piston has been channeled

Can you notice any seat of pants difference from this piston arrangement?

**Krazymaan** · 12-01-2017, 11:03 AM

Originally Posted by Captain75

Can you notice any seat of pants difference from this piston arrangement?

I won't be running it until next summer

**Captain75** · 12-07-2017, 10:29 AM

Originally Posted by Krazymaan

If your going to do a more performance motor later on. This is the time to practice. you really only need a gram scale. and sanding type tools. But if you weigh the rods, make sure you have a stationary peg to hang the rod off of and the other side on the scale and weigh each end to the same weight, not just the whole thing. Easy stuff. Youtube it.
You can go all the way to this extreme if you want too.
Even the piston has been channeled

Looks interesting!
I didn’t think the rods could stand these kind of drilling mods...