Merc Racing 575 SCI running very rough/rich
 

Hello All,

I just brought my 31 Bullet down to Fort Lauderdale and ran it for the first time this past week. The boat has always run beautifully and the first thing I had done was to have a 100 hr service completed. I had all the fluids changed and brand new plugs.

However the first time the boat was started there was clearly something wrong. The service company has hooked up scanners and everything checked out fine. But there still is a problem of running rough and too rich. I was out on the ocean and was able to run it at higher RPM's but when I got back and brought it to idle, it felt like they were going to stall.

they pulled the plugs and they were completely fouled with just 40 mins of running. Not to mention all the embarrassing black smoke!!!

Could anyone provide any ideas? Would it have anything to do with saltwater?

thanks!!!

One engine running rough is one thing but you say both engines are doing the same thing; What are the odds for that going on!!! Did these guys play with your ecms??? or make any adjustments to both motors ?What did these guys have to say about the problem ??
Jim





Oh yeah ,by the way who changed the plugs and were the wires changed ?

How old is the fuel in the boat?

Dump the separators out in a clear container and see what settles out. If it is white it the fuel is phase separated

I'd check to see what plugs they put in. factory replacements are NGK 5673-8

Mine did the exact same thing. It was a bad MAP sensor. You can pick one up from NAPA. part # 2-16865

Both at once though?

No, mine was only one motor, swapped MAP sensors and found the problem.

Keep it simple. It ran fine UNTIL they touched it. I would check the spark plug part number AND spark plug wire routing. I'd also check the distributor cap/rotor, and anything else they may have touched.

Black smoke dumping out the exhaust, my guess is it has to be running like chit. I wouldnt recommend any more 45 minute rides until you find out what the problem is.

I bought the same MAP sensor but I wanted Mercury quality. I think $400 was a good price on it.