Black sut on transom

[Hooter]

My 1999 Mercrusier 350 260 hp 2 barrel carb is runing fine but I just noticed black sut building up on the transom. Any suggestions to what maybe causing this problem

 

[mestey2004]

Re: Black sut on transom

I've got it too on my 305, I'm just assuming it is burned oil residue. I know my compression is fine, but you might want to check yours. You may have excessive blow by on one or more of your cylinders and the buildup is from that. Or I guess you could be running a bit rich and that would timing issue.<br /><br />just guessing really

 

[Bondo]

Re: Black sut on transom

It's been My experince that Merc. likes to set-up their motors on the Rich side.........<br />I've Leaned mine out Quite a Bit..... 2 or 3 needle sizes........<br /><br />You May have to dig into the Carb,+ Lean it out a little........<br /><br />Also Check to be Sure that it's Not having it's Air Flow blocked at the Flame Arrester, or by Anything Else...........<br /><br />I'll Also Bet that your Plugs will be Black,+ Fouled............<br />When you get it Properly Tuned,<br />The Plugs Should be a nice Coffee + Cream Brown.............

 

[butlp]

Re: Black sut on transom

Hooter,<br />I had the same problem with my 1997 4.3GS and found that the idle mixture was way out according to my manual. That's where I would start before assuming it's something major.

 

[Hooter]

Re: Black sut on transom

Black sut update, My boat broke down thought it was the carb so I took it apart and messed up the gasket. It ended up Being the timing sensor. So I cleaned the carb and replaced the gasket. It now starts better but I have the black sut problem. I did not change any carb settings

 

[Bondo]

Re: Black sut on transom

thought it was the carb so I took it apart and messed up the gasket...So I cleaned the carb and replaced the gasket. I did not change any carb settings

That, I Think might be the Problem..............<br /><br />Cleaning + Reassembly is Usually enough Trauma to make the previous setting Null,+ Void.......

 

[Hooter]

Re: Black sut on transom

Bondo, Do you suggest checking the settings. I did replace the float needle and checked the float setting. What settings do you think need adjustment? Tnanks Hooter

 

[butlp]

Re: Black sut on transom

When you say it "starts better" does that mean you don't need to advance the throttle as much as before or at all to start. This would be a sure indication of an over-rich idle mixture.

 

[Hooter]

Re: Black sut on transom

Lost Canadian, Exactly I use to have to advance the throttle a 1/4 to start it. Now It starts without any throttle advance.

 

[butlp]

Re: Black sut on transom

Hooter,<br />Sounds exactly like my boat when I purchased it. I followed the manual, mine is a 4 barrel (both idle mixture screws fully in and out 3/4 of a turn) then it would only start with 1/4 throttle. I checked with my local dealer and he confirmed that this was the correct procedure.<br />Find out what your particular motor setting should be i.e. buy a manual and spend 1/2 hour setting the carb and the soot will be gone.

 

[Masher44]

Re: Black sut on transom

That is something nearly unavoidable. Merc has had mine in 3 times for various adjustments and you will most likely always experience soot. You can limit it but I would be careful with leaning it out too much.

 

[Hooter]

Re: Black sut on transom

Thanks Lost Canadian

 

[Hooter]

Re: Black sut on transom

Masher44, I never expeirenced the problem until the mechanic replaced the timing sensor. I was in a hurry to get the boat back and he told me that he did not have time to check the timing. But he said the repairs he made should not effect the timing. Now I'm beginng to wonder.

 

[Masher44]

Re: Black sut on transom

Do you have a thru hull exhaust? / or silent choice? My problems supposedly were with a computer setting. The engine should run a little rich (safer) a sponge and soap is much cheaper than an engine. The thru hull question will answer alot.

 

[Masher44]

Re: Black sut on transom

The sensor might just be the ticket to all the problem.

 

[Hooter]

Re: Black sut on transom

Masher44, No thru hull exhaust or silent choice.

 

[Masher44]

Re: Black sut on transom

Well it sounds like the timing. I didnt want to mislead you earlier but I am still a believer in running just a little rich. If you get it in front of someone who can set the carb, you should like the results.( my brother is here and he just set his carb this Spring and he said it made a huge difference.) I was under the impression you had thru hull....sorry and good luck.

 

[Hooter]

Re: Black sut on transom

Thanks Masher44

 

[butlp]

Re: Black sut on transom

My manual gives a detailed procedure to set the idle mixture and I don't believe the engine is running too lean if you follow it. Mine was so bad that it used to smoke when you started it and you could smell it at slow speeds. I pulled my plugs after a long hard run and they were nice and coffee + cream brown which tells me the main jets are correct which is far more important than the idle setting.