300XS bore scuffing

[mercman867]

I felt the ports of a blown 190 hour 225 optimax block that was laying at a dealer, they are wayyy smother then mine and the cross hatching is much more visible then my 60 hour motor. I doubt that its an oiling issue as all roller bearings are drenched in oil.

[XstreamVking]

I would trust chaz's opinion 100% myself. Seems to trace the damage to the most likely cause.

[cali kid]

I turned on the motor first time myself and showed 120 mins of break in left. Did the break in myself too and i did consume a lot of oil.

Im thinking motor ingested some debris from the plenum. I’m tearing down the powerhead on Friday and will know more.

I’d expect that type of scuffing on all bores to cause some loss of power.

Metal from the ring gear and starter. Not worth tearing it down for. Wait for a more significant reason to tear it down, unless you have alot of time on your hands.

[Merc 2.5]

Metal from the ring gear and starter. Not worth tearing it down for. Wait for a more significant reason to tear it down, unless you have alot of time on your hands.

Man I really dont wanna sound like a idiot but why in hell would ring gear or starter have anything to do with bore scuffing. .maybe I've read it wrong .... theres many carb mota and horn motas(no airbox) runnin round with little to no scuffs

[KIRCHNER]

Man I really dont wanna sound like a idiot but why in hell would ring gear or starter have anything to do with bore scuffing. .maybe I've read it wrong .... theres many carb mota and horn motas(no airbox) runnin round with little to no scuffs

IF the cowl was left off in a dirty sandy area for an extended time could sucked in dirt, but too likely, ide get on the horn with mercury asap. ive got a 89 2.4 with waaaaay cleaner bores than yours. if u can feel scuffs there wasted. thats like .002-003 deep.

[Chaz]

Thanks Chaz, in fact, I inspected all ports and they are very sharp. I nerly cut my finger by rubbing them on the ports. No port prep is visible!

Which are the best aftermarket sleeves I can use for my 300XS?

The motors that say "racing" on them usually get pulled off the line and go thru a little extra hand grinding / sanding before they get put together. Yours looks like it got pulled off the line and was never finished.
The left side transfer has a chamfer , but the corner also has a hook that never got blended. Right side, which was obviously making metal is hard to see the bottom. And like I said , top-front looks to have tiny chips broken out of the corner .. might be the pic, could be my eyes. The exhaust port floor does look very sharp, and the ring has been cutting away at the right side corner.

Mercury wty ... Sir, why did you take the heads off yourself ??? If you felt you had a problem with your motor you should have taken it to one of our dealers ???
Ane even then, if it aint broke .. they got no reason to fix it.
You can try, they will have a rep come look at it ............
If he say's yes it's a developing problem, they will either put a new or remanned powerhead on. Whichever that still have in stock. if he says no. Get his boss's phone number. Two or three of those ... and they will replace it.
If they play the "you took the heads off card" you can (*&^^*(%$ them for a while. We already know that they are (*&$%*()(*%% &&^$$*(() So you will be preaching to the choir .. The easiest thing to do at that point is to just slip it apart and prep it like it's yours instead of flying down a conveyor belt ...

[Dave Strong]

Chaz you looked at them pictures way closer than I did. Good call on the piss poor port finishing. Guess I shouldn't be on my phone driving home from moms house. the rest of what your saying about self diagnosing stuff under warranty is so true.

Dave

[tux974]

Chaz you looked at them pictures way closer than I did. Good call on the piss poor port finishing. Guess I shouldn't be on my phone driving home from moms house. the rest of what your saying about self diagnosing stuff under warranty is so true.

Dave

His eyes are fine! Heck, his screen at home it's real BIG so that he can carefully inspect things.....
I have also seen similar scuffing from improper cleaning before assembling. Rule of thumb here.....clean the block one more time after it was just cleaned.....

[cali kid]

Man I really dont wanna sound like a idiot but why in hell would ring gear or starter have anything to do with bore scuffing. .maybe I've read it wrong .... theres many carb mota and horn motas(no airbox) runnin round with little to no scuffs

Just a guess. If the key has been touched with a running motor or bendix is slow to engage, hard metal is made rite where the intake horn is. Not scuffing, scratches. It's hard to believe Mercury racing, a cut above normal production would send out a high dollar piece with such a flaw.

[XstreamVking]

Any thing coming into the intake would have to not get stuck in the oil coated plenum, then make it past the oil soaked reeds, past the oil drenched crankcase into the bores.

[Dave Strong]

His eyes are fine! Heck, his screen at home it's real BIG so that he can carefully inspect things.....
I have also seen similar scuffing from improper cleaning before assembling. Rule of thumb here.....clean the block one more time after it was just cleaned.....

I'm a freak about cleaning when assembly of an engine is involved, was told a long time ago it's never to clean.

Dave

[Chaz]

His eyes are fine! Heck, his screen at home it's real BIG so that he can carefully inspect things.....
I have also seen similar scuffing from improper cleaning before assembling. Rule of thumb here.....clean the block one more time after it was just cleaned.....

Mama thought I lost my mind when I taped tracing paper over the screen and started drawing the outline of parts ... till we started sellin them ..

[TEXAS20225]

i think lack of champering caused your motor to manufacture the grit that scored the cylinders ! when rebuilding the grit comes from every where in machining also from sealing rings that need be removed and grooves cleaned out, reed plates are a big culprit of getting stuff inside,it just looks not finished in MHOP. down here in Texas we have a big problem with dirt dobbers building their nest inside of cowlings the nest are mud when they are building them but when next year rolls around the boat owner who never checks anything except gas gauge have the now dirt nest coming loose falling into bottom cowl and being pulverized into dust by motor vibration and being sucked into engine and before long its really toast ive seen them so bad that all cross hatch is gone and big wear on crank journals rod caps basically everything inside motor is junk

[Dave S]

Yes on the Dobbies..... and some reed chips ?

[tux974]

I do agree from pictures the ports look sharp.

After machining especially a used block finding that fine debris stuck to oil behind ports common. Hence the dumping methods multiple times with clean soapie warm water works.
IMPO properly cleaning plenum, VST, injectors, intake, reeds etc is important in a fresh rebuild.
I have seen were guys just take a motor apart put parts in totes and just bolt things back together when block is ready without cleaning or properly inspecting each and every part or wiring.