OMC Tech - Help

[Revenge22]

Paul i'd do some running voltage tests at this point. Coil primary extenders and a DVA adaptor and see if the voltage is holding steady when it's surging. gotta test each ignition coil. then i'd test the timer base (4v i think) and resistance. then work your way through the stator because it sounds like it's getting fuel. if everything is fine, i'd "rent" another power pack and see if that fixes it, or swap it with the port motor.

[PaulO]

No offense taken!!

[PaulO]

Revenge22, thanks for your reply. Don't know what a coil primary extender is. I can test the primary and secondary sides of the coils or probably better yet, swap the coils out from the good motor. I think I can find specs to test the timer base ( not as easy to swap out ). Paul

[racer]

Doubt it is an ignition issue if engine will turn full RPM and timer is moving ( with correct timing ) You mentioned trying a similar prop, what happens if you run a prop that slips down low? Is any fuel spitting out the carbs? Run engine until it is warm and shut it off with carbs shut and then open butterflies to see if you get any white smoke out of them, this would indicate reed or reed gasket issue.

[Revenge22]

Paul: CDI sells the extenders that allow you to hook up a multimeter to test running voltage. Just an idea. It doesn't sound like coils, and Racer I was thinking something in the pack or stator could be shorting to ground, or the sensor coil not putting out a proper signal to the pack but i'm positive you know more than i've forgotten and have helped me in the past! i did have an issue with my stator causing my 93' 225 to miss at random times, hence my thinking on this one.

[Motv18]

If it revs in neutral, but doesn’t under load. Look for fuel or air.

check the lever on the enrichment

if hitting enriched when it bogs clears it up it’s lean.

now weather it’s vro or carb ect will be tough to find.

gap test the spark and look for week spark. That would be more miss under load though so maybes not.

[H2OPERF]

I'm with racer... if its turning up on top most likely all the electrics are good, I/ we are assuming this is all stock carb size with airbox and all still intact? The test you did with the brake cleaner kinda tells you the idle mixture is off along with the idle / starting issues its had even if its running halfway decent now. When i worked on these more i would do idle balance tests like that to see what cylinders were carrying the load persay to me only way to get it right so they will start idle good along with timing depending on how deep they sit in the water. Anyway the gaskets under little covers on the sides of the carbs often get over tightened (smashed) and leak air which will cause issues on the low end circuits...also when you clean the carbs u need to spray something thru the little brass low/mid pick up tubes to make sure they are clear. If all this is good throw some screws in the mid air bleeds and see what gives worst case it will go fat rich.

[PaulO]

I don't know much history on this motor. Bought it as a package and a project. Took over a year to get the boat in shape and back in the water. Previous owner said powerheads were 250s but I don't know and have no way to verify. Don't even know what the difference is. Starboard motor has had running issues of one kind or another as long as I have had it and that totals only a couple dozen outings. Carbs are clean. I know the brass pickup tubes are clean because I have cleaned them all and found 2 clogged. It had a problem where it was running well unless it idled for an extended period and it would run out of fuel. Chalked that up to a bad vro and replaced it with another one (used. I have a parts motor) and that solved the dying at idle problem but started a carb overflowing issue with 3 carbs. Solved that by adjusting float heights. After that it would and does idle forever, runs great on top but has this intermediate problem. Went out and removed cowl and airbox. Worked the throttle from the motor, ran the boat at idle in gear and attempted to run it up in rpm while observing things like the throttle opening and the timing advance. Tried manipulating the timing advance to see if introducing more or less timing sooner would help. It didn't. Tried same thing with carb butterfly opening to see if more or less would help at bog time. It didn't. Does not spit out of the carbs and does not sneeze at all. Only thing I found that makes a difference in introducing some enrichment during acceleration with the enrichment valve. That makes it a bit easier to get it past the bog speed. BTW, when the motor idles and the throttle is opened, it immediately picks up rpm until about 1200 or so. I can run there nicely but if you try to increase throttle more, the motor dies. As you increase the throttle beyond the 1200 rpms, it begins to run rough and shake but no sputtering or sneezing. If you can coax it beyond the crappy rpm range it smooths out and runs up to 6k. It will run all day until it is slowed down to idle again. If this was a car I would be looking at the intermediate circuit in the carb or the accelerator pump. I wonder if I am missing something with these carbs. How is the intermediate circuit regulated in these? The brass tube which appears to supply fuel for the idle circuit and (I assume) the intermediate circuit does not even appear to be an emulsion tube. Again, thanks for all your help. Keep them coming even if you are not sure it applies. Need all the brainpower out there. Paul

[mrichartz]

Does it make a difference if you cover the carbs one at a time?

[Revenge22]

chucking around ideas: the idle/intermediate circuit is in the throttle body, unless someone can chime in and correct me wrong. Are the bowls weeping fuel anywhere? as you know those can warp. Did you try doing a hard shutdown when it bogs and check plugs for fuel? It's possible it's loading up because the re-circulation lines are plugged up too. When the carbs were done, did the throttle bodies come off for cleaning as well? My 93' has core and expansion plugs, and one fell out causing a lean idle/intermediate problem but I don't think your year has those. just needs to be clean. If it's not sneezing at all, i'd say its possible it's getting too much fuel.

[H2OPERF]

The idle jet is the adjustable screw down in the hole, the mid jet is the air bleed above it prob has like a #30 in there, what i was saying above put screws in place of the air bleeds which will make the mid circuit go really rich...if it wont go when plugged you probably have other issues. The link/synch is really critical on the part of all carbs closed tight at idle with a gap on the pickup roller/cam and crack open at the same time. If you move the carb pick up roller away from the cam, larger gap, it will also cause the low end to be richer also. On the old big bores i even changed the brass tubes on the mids they are smaller on the end inside the carb this was to help on accel but that was a ported motor...

[gfinch]

OK. What If... What about making the enrichment cylinder specific. Plug all individual enrichment supply ports. Using the enrichment supply attach this hose one at a time to each cylinder. Keep in mind the amount of added fuel will be all 6 into that one cylinder.

[PaulO]

The idle jet is the adjustable screw down in the hole, the mid jet is the air bleed above it prob has like a #30 in there, what i was saying above put screws in place of the air bleeds which will make the mid circuit go really rich...if it wont go when plugged you probably have other issues. The link/synch is really critical on the part of all carbs closed tight at idle with a gap on the pickup roller/cam and crack open at the same time. If you move the carb pick up roller away from the cam, larger gap, it will also cause the low end to be richer also. On the old big bores i even changed the brass tubes on the mids they are smaller on the end inside the carb this was to help on accel but that was a ported motor...

Excellent idea. I will try plugging the jets. Again, thanks

[PaulO]

OK. What If... What about making the enrichment cylinder specific. Plug all individual enrichment supply ports. Using the enrichment supply attach this hose one at a time to each cylinder. Keep in mind the amount of added fuel will be all 6 into that one cylinder.

Very Smart! You and H2OPerf are on the same track. I appreciate it. Paul

[H2OPERF]

You can use round wood tooth picks and just poke in the jets for a temporary test but put air box on so they don't get sucked in if one falls out. have done this many times on the idle and mid with older fixed jet carbs while testing... Dave