Classic signs it's time to de-carb or worse
 

Your 6cyl 2 stoke carbureted engine.

Ok...lets hear it!

Thx, Bill

at least annnually

Thanks-looking for specific symptoms; stalling, hard start, etc....just what are the specific indicators it's time to decarb?

I get an occasional sneeze at idle. Not sure if that is related, but after I do an annual decarb it doesn't happen any more.

been running good for a year, its time to decarb, no reason to wait for symptoms

I decarb every new customers engine when I first service them. After a good heavy decarb, they only need a annual decarb on average. I also recommend running Yamaha ring free or mercury carbon guard in every tank(reduce the ratio, Anytime I pull plugs on an engine, it gets a heavy shot of mercury power tune. Optimax owners I tell to run a portable small fuel tank with a heavy decarb mix in it to their engine and run them at least 20 minutes on it, let it sit for a couple hours, then switch back over to their regular fuel. Do this every season or 100 hours

Thanks for all feedback spare

I was given a can of omc spray decarb
I soaked the carbs last night
Will pickup some seafoam on way home tonight too

I have been doing a LOT of trolling for stripers and assume this is probably worst case for these engines?

Here's what happened: last weekend while running down the bay at 4K after about 1/2 hr engine loses rpm. I back off
Check everything
Seems ok
I turn around head home running about 3.5 k no problem
All is well

Next day check fuel filter, oil etc
Looks fine
Run down bay 4K
Exact same spot it happens again

Run back to dock 3.5k no problem

Check everything again
Looks good
Did the decarb last night
Letting it soak

Will dump seafoam in fuel also

Tx
Bill

Not carb...what else?
 

So I did the decarb thing and am still having this same issue...so it likely is not carbon buildup.

Here's what happened: last weekend while running down the bay at 4K after about 1/2 hr engine loses rpm. I back off
Check everything
Seems ok
I turn around head home running about 3.5 k no problem
All is well

Next day check fuel filter, oil etc
Looks fine
Run down bay 4K
Exact same spot it happens again

Run back to dock 3.5k no problem

Check everything filter, fuel line connections, etc again tonight. Fire it up, run down the bay,same thing; cuts out losing rpm, bad vibration. Check ball-it's fine. Hit choke button-no change.

Shut it off, re-start and am able to run home at low rpm running smoothly.

So it runs fine for about 10 mins, then repeats the above scenario-3 times in a row.

Thoughts?

Tx
Bill

How do decarb ? Do you have to remove the carbs?

when u say runs back at 3500 fine, does that mean your holding it at 3500 or all it will do is 3500?

conventional wisdom is fuel, fire, or compression. you think you've checked fuel with the decarb, so next thing i'd check would be fire. get a fire fly spark tester and check. coil might be dropping out after it gets warm or plug.

Looks like ECU is shutting down to safe mode. Boat is pulled and more testing after the holiday:embarsed:

Def electrical...coil...or ECU? Will find out soon....

Thx All