Logo
FULL SITE MENU

25 merc rebuild

C

cordgrass

Contributing Member
"this rebuild was not planned

"this rebuild was not planned i have a 25 merc. and the lower unit went out a buddy of mine said he had a 25 at his house with a broken crank and no carb so i bought it for 150. I thought about selling the parts but deceided to keep it and rebuild. problem the motor is in a thousand pieces. i took the good looking parts and put them on my running 25. heres a pic of my running 25

url]

url]



heres the pieces of my other.

url]


url]



first fix with new crank.
url]
"
 
"What do the cylinders look li

"What do the cylinders look like?

Since this motor has Merc's "headless" split block design, if the one of the cylinders is all scored up (worse than a simple hone job will take care of), all you have is a few pounds of scrap aluminum. You just can't bore these split block heads.

Merc never intended these to be bored out, so they never even produced an oversize piston or rings.

It may look like a jumble of parts right now, but a Seloc's manual will give you a very good step by step of how to put her all back together. It really isn't that tough.

However, be prepared. If you go with OEM parts a piston/rings could run you 200 bucks. New rod bearings (which must be changed if you crack her open - so you are way past that point now) will run 60 bucks for the pair. Add in gaskets, seals a wear sleeve for the crank (plus maybe main bearings) and this "project" could well top the 400 or 500 dollar mark.

I wouldn't try and talk you out of it, because it is potentially a great project which could produce an outstanding motor.

But that is exactly why Merc's 1980-something on, 25 horse and under motors are generally scrapped rather than rebuilt (within their limits). The numbers just don't add up - costs more than what the motor is worth...."
 
..."New rod bearings (

..."New rod bearings (which must be changed if you crack her open "

Why if they are in good shape? Been reusing them for years in other Mercs.

Jeff
 
"My manual states that - "

"My manual states that - "even if they appear to be serviceable, they must be replaced" it goes on about if that is not possible that they must go on the same rod that they came from or very bad things will happen.

For the sake of 60 bucks I have never bothered to question that - especially since it is rare that you have to completely tear down the upper block on one of these (the crank seals (usually the only thing you need to go in after) can be replaced while leaving the rods connected if you fiddle around a bit).

That statement applies to all split block mercs built pre-95 up to and including the 25 horse models. So pretty much all the 6, 8, 9.9, 15, 20 and 25's out there in that model run."
 
"I'll bet good money you c

"I'll bet good money you can mix and match good, used needles on all of those engines without the slightest problem. After all, what is the difference with them and the older engines--and we ALL mix and match those without a problem. Futhermore, installing a "new" bearing requires also replacing the inner and outer races as well; and that means a new crank and rods everytime. NOT!

Lots of BS in manuals, and profits are made from new parts!


Jeff"
 
Back
Top