3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

I am having an issue with a 3.7 Mercrusier. OK so I have a boat that sat for 7 years without running and wasn't properly winterized so I have been dealing with a varnished fuel tank. I have replaced plugs, wires, rotor, points, cap. We took out and it ran Ok and then died when we idled down. It started up after a few minutes of coaxing and then ran flawlessly. The boat sat for a few weeks and then I went to fire up and it ran rough. I figured it just needed to ba ran out so I took to lake the next day and it started right up and then died. I tried to get it running and it just struggled to start. The fuel filter looked plugged and so I ran to town and bought a new filter but she wouldn't start. I thought it didn't have good spark so I replaced the wires and it started right up and seemed to run with real improvement. I was getting some black smoke but figured it was a mixture issue so I took to lake again this last Sunday. Got it next to the dock (kids and wife loaded up). It started up but would not idle. I was getting all kinds of black smoke and it seemed to flood. We also noticed the exhaust appeared to be really psuhing a lot of water up directly behind the boat and it wasn't coming our of the prop (it looked like it was exiting the out drive?). So we pulled from water and there was black film on boat hull. I can't seem to get this boat in the water to cruise and I despite all the hard work about to put the darn thing up for sale. Anyone that can provide help, I would deeply appreciate it!

Thanks

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

You state that it wasn't winterized properly.
Do you know that the block, heads, manifolds, and risers survived without cracking?

The black smoke and film could easily be from an overly rich fuel mix, misfires, or something simple...
but I would make sure I do not have any major trouble before going to much further.
No sense in performing a tune up on an engine with major damage.
Compression test...?

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

Check and make sure your automatic choke is working (opening when warm). If stuck closed or mostly closed it will sure cause black smoke, and poor running when warmed up. Could also be a faulty fuel pump diaphragm. Is there any fuel coming out of the clear hose between the carb and the fuel pump?

What year/model number is your engine? Serial number would help too.

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

rschap1 said:

You state that it wasn't winterized properly.
Do you know that the block, heads, manifolds, and risers survived without cracking?

The black smoke and film could easily be from an overly rich fuel mix, misfires, or something simple...
but I would make sure I do not have any major trouble before going to much further.
No sense in performing a tune up on an engine with major damage.
Compression test...?

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It is a closed cooling system and it had anti freeze in the system. I have changed the oil and the oil is perfect - does not have a cracked block. As far as I can tell there has not been any water in the system and it ran like new on our maiden voyage (after intial fuled problem). When I stated that wasn't winterized properly I should have referred to the fuel system. Everything else seems to be in working order (of course I have been wrong before).

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

Could also be a sticking float in the carb.
If you added fresh fuel (that dreaded E10 devil) to your old fuel, chances are the devil is now washing all the varnish out of the tank and lines, and it's all headed down stream to the carb. Might want to pull apart the carb for a re-build, and stock up on fuel filters.

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

RogersJetboat454 said:

Could also be a sticking float in the carb.
If you added fresh fuel (that dreaded E10 devil) to your old fuel, chances are the devil is now washing all the varnish out of the tank and lines, and it's all headed down stream to the carb. Might want to pull apart the carb for a re-build, and stock up on fuel filters.

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I am on my secon fuel filter. There wasn't much gas in tank but the fuel tankl was open so not sure if someone started project before me or not.

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

Don S said:

Check and make sure your automatic choke is working (opening when warm). If stuck closed or mostly closed it will sure cause black smoke, and poor running when warmed up. Could also be a faulty fuel pump diaphragm. Is there any fuel coming out of the clear hose between the carb and the fuel pump?

What year/model number is your engine? Serial number would help too.

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3.7 1990 Bluewater. I will get ser# tonight. I also should have pointed out that the there are two purle wires witha plug that is dangling behind carb. I think they belong to automatic choke but annot locate a socket they go to. There is a "hole" behing the carb (I can't see very well) that I though it plugged into and it doesn't fit in there.

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

frankttaylor said:

3.7 1990 Bluewater. I will get ser# tonight. I also should have pointed out that the there are two purle wires witha plug that is dangling behind carb. I think they belong to automatic choke but annot locate a socket they go to. There is a "hole" behing the carb (I can't see very well) that I though it plugged into and it doesn't fit in there.

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My typing is terrible. The one class I skipped every day in high school and needed it the most. Purple wires!

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

frankttaylor said:

3.7 1990 Bluewater. I will get ser# tonight. I also should have pointed out that the there are two purle wires witha plug that is dangling behind carb. I think they belong to automatic choke but annot locate a socket they go to. There is a "hole" behing the carb (I can't see very well) that I though it plugged into and it doesn't fit in there.

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89 was the last year of the 3.7 engine, so you probably have an early built 90 boat that got the last of the 3.7's.

Post a picture of your automatic choke, I would bet the terminal broke off. If that purple wire connection touches metal, it will short out the ignition.

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

Don S said:

89 was the last year of the 3.7 engine, so you probably have an early built 90 boat that got the last of the 3.7's.

Post a picture of your automatic choke, I would bet the terminal broke off. If that purple wire connection touches metal, it will short out the ignition.

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I will take one tonight. That would probably explain why I had an ignistion problem also. Would this cause it to run rich?

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

frankttaylor said:

I will take one tonight. That would probably explain why I had an ignistion problem also. Would this cause it to run rich?

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Sure it would run rich. Without the wires on the choke, it never opens the choke. It would always be trying to stay closed and at low rpm it would flood a warm engine big time.

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

Don S said:

Sure it would run rich. Without the wires on the choke, it never opens the choke. It would always be trying to stay closed and at low rpm it would flood a warm engine big time.

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OK I will take a picture then. Then we can go from there.

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

It should look something like this one. Note the metal tab. That is where the wires should hook.

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

Don S said:

It should look something like this one. Note the metal tab. That is where the wires should hook.

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I am fairly sure that that tab is missing/gone. What does replacement entail?

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

Replacement involves 3 screws, will take you about a minute. Part appears to be still available, ~$120 though. May be better off buying a spare carb off ebay or seeing how broken yours is...

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

nola mike said:

Replacement involves 3 screws, will take you about a minute. Part appears to be still available, ~$120 though. May be better off buying a spare carb off ebay or seeing how broken yours is...

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I think I will pull carb - rebuild it and see if I can fix for less rthen 120.00. We have boat salvage yards maybe they will have one? Does anyone know if these are the same on different motors or are they engine speciific?

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

frankttaylor said:

Does anyone know if these are the same on different motors or are they engine speciific?

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Meaning the choke/cover or the carb? The choke cover should be the same, at least on the 2bbl mercarbs/rochesters. The carbs themselves are similar, but would need the correct sized jets for your application. There's a mercarb on ebay now from a 170 for $80...

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

nola mike said:

Meaning the choke/cover or the carb? The choke cover should be the same, at least on the 2bbl mercarbs/rochesters. The carbs themselves are similar, but would need the correct sized jets for your application. There's a mercarb on ebay now from a 170 for $80...

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I was reffering to the terminal as far is they are inter changeable.

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

Why would someone buy an old carb on ebay for just the choke cover and not even know if it has a good choke cover or not? :facepalm:
Here is the cover from right here at iboats for less than 75 bux. It shows out of stock, but call and find out if it's been restocked or they have a sub from another company.

http://www.iboats.com/18-7665-Choke...2631415--session_id.152138369--view_id.709106

Re: 3.7 Black Smoke - Exhaust issue (I think) - Boat Ramp Hell

Don S said:

Why would someone buy an old carb on ebay for just the choke cover and not even know if it has a good choke cover or not? :facepalm:
Here is the cover from right here at iboats for less than 75 bux.

http://www.iboats.com/18-7665-Choke...2631415--session_id.152138369--view_id.709106

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'cuz it's probably ok, and worst case, you get a spare carb. Which is very nice to have.