Omc Idles Really Rough?? Fresh Block Please Help!!

[baja200merk]

I JUST PUT MY ENGINE TOGETHER ITS A 1994 JOHNSON VENOM AND IT HAS A FRESH POWER HEAD (OPEN DECK)

the problem is the thing idles like chit! vibrates coughs and wont idle under 900rpm in gear
if i give it gas it bogges up to 2800-3200 and wakes up and screams but untill that rpm it runs horrible..

keep in mind im runing about 40:1-35:1 mix and it smokes alot untill about 2500rpm..

my question:
could the idle jets be too rich and the high speed jets ok??
i replaced the plugs and they were drenched i mean dripping!
could it be timing? i have never checked timing do i need a light?
i have a service manual but they are saying to use an omc tdc special tool and some kind of omc ignition sensor

TIA kevin

[supergenius74]

If your jets are still stock size then you shouldn't have these kinds of problems unless there is something clogging them. !st check your compression with a GOOD compression guage, I say good because I used and el-cheapo one last year and it was wrong because it leaked. Make sure your cyl don't vary too much, mine varried by 10 psi and caused it to have a terrible idle and loose power in the top end. If compression is good then check your coils and check your plugs makes sure everything matches and works properly. Anything wrong with your spark and it will idle bad but run pretty good in the top end. spark is alot more complicated than just looking at it. My evinrude had 2 different styles of coils and therefore needed 2 differnet type of plugs in it and it ran great after that. Don't assume that if you can see a spark then everything in the ignition system is good. If you are backfiring you are most likely igniting when you aren't supposed to and that can becaused by several things. just my .02$

[lokinutz]

How much of a difference will plug brands make on these things. I have an 88 200 XP running cross ref. NGKs...will running the recomended brand make a diff? Don't have any probs, but want to keep it that way.

[racer]

Baja if that is the engine with the carbs off that 92 25 inch engine you had they may need to be rejetted but it sounds more like a sync/link problem.

Lokinutz, If you have the vro I would only run the supressored standard plug as it gives off less interference and will be less likely to effect your oil warning.

[lokinutz]

No VRO, but didn't know about the supressor plugs. By the way, saw a new 22 Stoker this weekend in Topock. Have you rigged any with twin OBs? Might have to be my next boat when I outgrow my 20SST(which may be never).

[baja200merk]

Originally posted by racer
Baja if that is the engine with the carbs off that 92 25 inch engine you had they may need to be rejetted but it sounds more like a sync/link problem.

Lokinutz, If you have the vro I would only run the supressored standard plug as it gives off less interference and will be less likely to effect your oil warning.

yea it has the carbs from the 92 225 evinrude
wat do you mean by snyk/link??
where do i start looking?

[capnzee]

Any possibility that you have a reed stuck open?/or sucked something into the intake side of the manifold when rebuilding. If all of your jetting etc has remained the same as before the rebuild, I would suspect something like a broken reed or a reed that may have partilly injected something that is holding it open, or a reed that was bent open during the rebuild, anyway, you get the idea. Capnzee

[baja200merk]

thats a possiblility but i think there is a knock in the engine my dad says im being paranoid but i dono... its got 8.5 hrs on it now and i gave it a quick blast to 5k and it was right there but im only running 19' pitch and last year it would almost pin the tack at 67-6800rpm with the 19"

the tempest is 25p so ill need the bottom end power (that im lacking) to get the boat outa tha hole...

i have alot of work so i dono when ill be able to screw with it
I HOPE ITS NOT BLOWN!!!!:mad: :mad: :mad: :eek:

[outboards4life]

synchonizing your carburetors with your timing. Just making sure that your carbs aren't open to far for what your timing is set at.

[baja200merk]

how do i tell if the timing is not in sync with the carbs

i had all the linkage loose the other day and made sure all the carbs were staying closed and openin at the same time and they are..

this block is an open deck block my original 1994 johnny block was a closed deck block and originally had small bore carbs... but i broke them and put these mid bores on the block im running now (which must be an older block because its open deck) and it runs reall rough at idle... could the mid bore carbs idle jets be too big and the top end jets are good size?

what would happen if i pluged the mid range jets? would it be worth it?

[baja200merk]

SMOKED IT #3 AGIAN... DONO HOW!

[pyro]

You've got the worst luck... Sorry to hear....

[baja200merk]

ur not kiddin!

[Jay Smith]

Sorry to hear of your continueing problems ,
I would have to agree with Capnzee with a reed failure the piston drives down to create primary crankcase compression and if the reed valve is not intact or sealing the fuel vapors that are being compressed to loop around the sleeve and enter the top of the piston to cool , lubricate, and be ignighted are speued out the front through the leaking reed causeing the motor to run lean and without any anti detonation or lubricative propertys the fuel oil vapors have thus smoking that bore. I would look at that possibility very closley. Hold the reed cage up to the light and if they are cracks that is where the charge is going instead of where it needs to be routed.

Maybe that will help,

[baja200merk]

yea i think you were right jay!...
i cansee right through the reed cage on #3 but these are boysens.. so i cant just replace the one wit stock reeds i have to replace them all, igot alot of crap in there recently but the one of the reeds for #3cyl is real wacked and dont close at all even after cleaning it out with air compressor, gunk and some q tips... i cant get it to make that poping noise like the rest of them do... oh well need new ones thanks alot!

new plan.
i got another complete power head 1992 225 open deck.

compression is between 80-100psi im gonna throw it on with new reeds and the mid bores that belong on this new power head, ill keep you guys posted!! thanks for your help! any other suggestions?