Classic signs it's time to de-carb

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BillTex

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

Your 6cyl 2 stoke carbureted engine.

Ok...lets hear it!

Thx, Bill
 
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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.
 
BillTex said:
Thanks-looking for specific symptoms; stalling, hard start, etc....just what are the specific indicators it's time to decarb?
Click to expand...

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
 
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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
 
tat engine doesn't have a computer per se, but it dies have electronics that will derate the engine from over heat or low oil. It should give you an alarm if either of these are occurring. Start off by checking the alarm circuit. Does it beep when you turn the key on? Find the temp switch on the cylinder head, ground that wire with the key on, it should sound an alarm. If the alarm is working, and your loosing power while running, next thing to do is run with a portable fuel tank. If it runs good with the portable, look at your fuel system. If not, Id check the electronics on the engine, most likely the powerpack. If you can get it to act up on a regular basis, you should be able to ground out one plug at a time and see if its related to one cylinder or another. If you are still suspect to an overheat issue, buy a temp gun from harbor freight, they are cheap and help a lot with diagnosis. Once you confirm its not overheating, you can disconnect the temp sensor and see if it does it again(bad sensor)
 
Sounds familiar to me I had the same thing happen to my Mercury, I would be driving then the RPms would cut in half and my oil alarm would sound that happened for about a month Running great than RPMs would cut in half, what it turned out to be was I have two power packs and the one that the alarm was hook to would stop working causing the RPms to drop if it happens on land check for spark your probably losing half your sparks to the plugs Like spare said check your power packs Good luck
 
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