is nikasil and chrome the same thing?

**eli** · 07-11-2004, 04:31 PM

in a 93 merc 2.5 for rebuilding purposes nikasil is expensive so is chrome ,how about plain bores with not so expensive rings ,i put merc gold ones in last june and there shot 100 hrs ,we dont run the boat any harder than my 200 fishin motor and that had over 300 hrs skiing and tubing and going fast i,m hearing all sorts of answers from different outboard builders on how to build the 2.5 merc i do my own assembly and have been for years,i cant believe only 100 hrs then redo with $4000.00 every year times 2. twin engine cat. i didnt think i had to do this every year,i have talked to other guys with 200/400 hours depending how you lean on it,if this is the way it is then the boat will be for sale. any help would be appreaciated. Thanks Jay.

**Jay Smith** · 07-11-2004, 07:16 PM

If you do your own assyembly the only thing that would be changed is the rings ( $375 ish ) and a gasket set ( $250 ish )....
$ 625 ea. motor is a hell of a long way from $4000 ???? If you do the work as matenience and do it before the motors need major things repaired because of neglect this is in the ball park for most rebuilds and can be done in one day ( each motor ) if your sharp and know all the procedures in tearing down cleaning and assyemblying your motors ! Don't know who's quoting you those prices but they are WAY out of the ballpark........The motors are going 120 -130 hrs before they need rings ( coated motors ) and are cheap to freshen but if the motors are neglected and the Nicom gets chattered due to clearance problems by running them to long the price jumps consideratable...............

good luck ,

**Techno** · 07-11-2004, 07:32 PM

A twinned cat and only run like a fishin motor? How do you control your self?

Stupid question but could it be something else? water pressure or oil or something like that? A failure rather than wear?

**Raceman** · 07-11-2004, 09:31 PM

What kinda oil and at what ratio?

**Jay Smith** · 07-11-2004, 09:49 PM

He was running 40:1 Mercury Preium Plus Norris...

**Raceman** · 07-11-2004, 10:31 PM

Damn. I wuz' hopin' for another "gimmick oil" dig opportunity.

**Travis Fulton** · 07-11-2004, 10:43 PM

maby cabelas premium

**sosmerc** · 07-11-2004, 11:50 PM

I think his question ("is nikasil and chrome the same thing?) is still on the table......
I'd like to know more about this myself.
Some of the little Merc 25hp motors were labeled "Mercasil" and they could be bored oversize. So just how many Merc cylinder materials do we really have out there?

**Jay Smith** · 07-12-2004, 08:54 AM

To my knowledge there are 4 bore surfaces that Mercury
uses (d ):

1. Cast Iron ( steel )
2. Chrome
3. Nicasil
4. Nicom

Chrome is nothing like Niccom or Nicasil nor can it be visually mistaken for them. It is pourous and pitted looking to trap oil , Nic and Nicom is a coating applyed to a Alum sleeve , cut to size and honed with a 5 sided diamond hone.............Honing the coated motors it is CRITICAL to use the correct hone speed , dept , and stroke or the rings will prematurely wear. The coated sleeves appear to be a slicker finish than steel but are VERY abrasive to the rings that is why they coat the plated cylinder rings with Tiatanium to prevent premature wear. Also that is the reason for thier short ring life VS. steel bore with the chrome ring on most fishing motors ! The fresh rebuild steel bore "looks" abrasive BUT the composisition of the bore is soft and the ring will actually knock down or smooth off the abrasion after only a few hours of running .The High Performance boater gives up ring life for the performance gain with the concaved ring in the Hi Per motors as friction is reduced power is increased. I was told several years back from Mercury that all things being the same a coated motor will make 12 more HP ( 1 1/2 boat length in the quarter ) than the same motor with steel bores.....

I have never witnessed a steel sleeved motor run "with" a coated motor ALL THINGS BEING THE SAME ( C.I. to weight ratio being the same, and no power emhancements { NOS , alky } )

from my observations,

**sosmerc** · 07-12-2004, 09:48 AM

Interesting information. I was not aware that Merc was using an aluminum sleeve...I thought sleeved motors were all steel sleeves.
Some more questions:
Can the nik and nicom be bored oversize?
Will the surface rust like steel if it sits around exposed to the atmosphere?
When did Merc quit using chrome?

**Jay Smith** · 07-12-2004, 12:47 PM

The aluminum sleeved Hi Performance can be bored and re nicomed an aftermarket piston and a compadable ring would then have to be found to be a "mate" to the nicom bore....Nothing on a "coated" motor block ( either half ) can rust ........

BTW ALL 260's, Drags. F-1's, and 280's are aluminum sleeved and then coated with the German Nicasil ( pre 1995 ish ) or the superceded Nicom ..........

Sorry I can't answer the chrome question I don't have alot of dealings with anything older than 1991 2.5's and do very little fishing motor and older stuff that is chrome........

Good luck !

**Markus** · 07-12-2004, 02:04 PM

Aluminum is too soft for a sleeve material since it will rapidly be worn out by the piston rings. Therefore an aluminum sleeve has to be coated with something that is harder. On high-performance engines, Mercury used Mahle's Nikasil coating up to the mid-nineties and then switched to US Chrome's Nicom. Similarly, Mercury coated the aluminum sleeves with chrome in 2.4 liter fishing engines. Since it is just a coating, it will be removed if the cylinder is bored.

A cast iron sleeve, as used in most other outboards, is the same material throughout. Therefore, it can be bored.

**sosmerc** · 07-12-2004, 02:51 PM

I was not aware that the early "chrome" motors such as say a 2.4 litre 1979 200 had any sleeves. I knew they could be sleeved if someone needed just one cylinder repaired and was willing to go steel along with the appropriate ring. But if the Chrome motors originally had sleeves then why couldn't they be repaired with a new chrome coated aluminum sleeve? I guess I always thought the older chrome motors were just an aluminum block that had a chrome coating applied to the cylinder portion of the block.

**Propelled Marine** · 07-12-2004, 03:56 PM

Steve, I think your right. The 2.4L "chrome bore" does not have a sleeve. You need to bore that cylinder to accept the new sleeve, and of course use the correct rings.