OMC V6 problem!

[looseunit225]

hey guys

we raced our first race for the season yesterday and had nothing but troubles!

skiers missed two starts than we got away!

once we had got away i noticed the engine not revving so i investigated threw my EGT gauge and found that the right hand bank was only running at 700 degrees and the other side running sweet at 1250degrees

so we nursed it to the turn arround point (we race to a point than stop for two hours and than race back)

at the turn arround point i pulled the plugs out and found number 3 to be black so in a made rush i changed the spark plugs and replaced the power pack to find absolutly no diffrence! checked that the cylinder was sparking and it was! ( dont know how strong of spark but it was firing!

the engine was still reving to 6,000rpms but just wouldnt rev any harder! and it also didnt seem to be missing or anything what do you guys think?

[looseunit225]

no ones really got any idea i take it! lol

well last night i replaced the coild checked compression 145psi checked for spark checked for anything that would be flooding out the engine!

so im going to change the trigger tonight and see what happens but if that doesnt fix it well than im pretty screwed for ideas!

cheers

[Woodduck]

What about your jetting? Have you tried giving Tony Rowe a call, did'nt you get the drop on off him? Or their is a bloke in Heidelberg who is real handy with OMC's. His name is Ian 9455 3665

[looseunit225]

i got the engine off tony but alots changed since than i changed the manifolds and reads and some other stuff i've also rebuilt the carbs since than!

jetting is all good and its way to far out to be the jetting as im nearly at the largest jet size you can get foir those carby's!

i've got darren spencer from Ace racing giving me a hand and well its got him stumped it all pointed to a power pack but we bolted a new one of them on already so everything is pointing to the timer base(trigger)

[racer55]

Sounds more like a stator problem, timer has 6 seperate triggers so odds of all 3 on one bank having a problem are slim.

[maloneyau]

check to make sure two of the coil wires are not mixed up on that bank. I have seen this before on these engines. The blue and green stripes tend to wear off the orange coil wires making it hard to identify one from the other.
Just a thought!!

[looseunit225]

racer 55 theres only one cylinder not firing on because the egts are on one side or the other!

and the number 3 plug is all fowled up and if i put a new plug in there!

and malon the power pack is brand new so the wire colours are all good!

[looseunit225]

sent the same twice

[looseunit225]

okm just spent a fair while out the ramp doing plug chops on the engine and found them to be perfect so the EGT gauge is reading incorrect!

but there is a reason why i have lost my speed! at 6200rpms it misses and starts to richen up its like it has a rev limiter!

any ideas bad coils maybe?

[looseunit225]

i have listed a small video of the engine testing with the test wheel on at the ramp and you can actually here the engine start breaking down at high rpms!

http://au.youtube.com/watch?v=0kM5CysOnck

[maloneyau]

Try another flywheel.
I had an engine do this once,
The engine I had, used to miss like this but clear up when you hit the trim button. I then dissconected the rec reg and it did the opposite (run good then miss when trimming) I replaced, CDI , coils, stator, rec reg and it did not fix it until i replaced flywheel. Not sure why but it worked.
give it a go.

[looseunit225]

hmmmm sounds interesting i might try and do that!

just gotta find another V4 fly wheel as i have a low amp ignition system!

[inshoreracing]

HI,

last year, i used a 3l carbs OMC.
On this engine, we haven't limited(6800) powerpack , but 8500 powerpack.
If you are interested I can give the OMC ref.

The engine is well but after 7000rpm, time to time I have like you(I think)
with this problem, I run the 24 hours of Rouen without break!!!

really, at this rpm you have more fuel on 2 cylinder.If you change and put little jet you broke the engine(it is my experience)

regards
jm

[looseunit225]

i have replaced the ignition system with a low amp ignition system so at the moment theres no rev limiter!

you will find in my engine theres stagged jet sizes for the 2 or 3 cylinders that are a bit richer than the other ones!

[omt14f3dse]

Hi Loose Unit, A couple of questions for you regarding rev issues. You said you have changed to 16 amp electrical system, are you sure the powerpacks are unlimited as 86 - 87 big blocks were limited to 6100 (pack # 583030 or 583605) the rest are 6700 limited. Second question is, are the carbs the same as when you ran 7000 rpm as there are two different bore sizes. the other thing to check is that you have the idle and intermediate jets around the right way, as inters flow fuel all the way through to top end. Inters are in the top holes. The rev drop indicated only one cylinder is not performing as you said #3 looked off so I would start with that carb. Main jets can come loose and vibrate back to bleed screw so make sure you use notched bleeds as then you wont lean right out on fuel if this does happen. Happy fault finding I will keep an eye on the post for any replys. Cheers DSE

[looseunit225]

Cheers DSE
the way the engine preformed was one weekend it was running arround at 7,000rpms and next weekend it started playing up!

it seems my EGT gauge has gone faulty on one side thats what was giving me the incorrect reading!

and the final conclussion that i can come up with is that it was bad fuel! i drained the tank and replaced it with new fuel and bingo the engine started to preform again!

[Powerabout]

check the magnets in your flywheel to make sure none have broken and hence creating an extra north south pole