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View Full Version : Grrr. Anybody think this isn't a carb problem?


strad
06-23-2013, 01:13 PM
Two weeks ago was the last time the boat was in the water, and at the time, it ran perfectly. This morning put it into the water, and first of all it was very difficult to start, and then once it did start it would not run unless the throttle was significantly open. Even after warming it up it would not idle. Needless to say we didn't leave the tie-up dock lol. I did check to make sure the choke was open after initial warm up and it was wide open (as it should be).

Boat smells like it is running super rich. So is a dirty carb the most likely cause of my problem? Or would you guys look at something else first? I haven't touched the carb since I bought the boat last September. I know the boat sat for a year without being run before that time. Should I just throw a rebuild kit at it and soak it real well?

It is a 351W running the 4160 carb.

rektek
06-23-2013, 01:43 PM
it sure sound like a carb issue, leaky power valves, contaminated fuel. something simple would be to check the fuel filter to see if it's plugged. any way to drain or see what's inside your tank ?

madcityskier
06-23-2013, 01:55 PM
If you want to look away from the carb, check plug wires?
Unburned fuel for n the exhaust, rough running, easy to check, easy to knock loose if you're in the motor compartment for any reason.

Cloaked
06-23-2013, 02:05 PM
Two weeks ago was the last time the boat was in the water, and at the time, it ran perfectly. This morning put it into the water, and first of all it was very difficult to start, and then once it did start it would not run unless the throttle was significantly open. Even after warming it up it would not idle. Needless to say we didn't leave the tie-up dock lol. I did check to make sure the choke was open after initial warm up and it was wide open (as it should be).

Boat smells like it is running super rich. So is a dirty carb the most likely cause of my problem? Or would you guys look at something else first? I haven't touched the carb since I bought the boat last September. I know the boat sat for a year without being run before that time. Should I just throw a rebuild kit at it and soak it real well?

It is a 351W running the 4160 carb.If the carb is an issue for sure, a rebuild is OK. I used to swear by a new set of carb gaskets but have changed my opinion somewhat after several rebuilds and life-expectancies of service disappointments. The carb is 29 years old.... budget allowable and you plan on keeping the boat for another 3 - 5 - 10 years, I'd spend the ~$500 for a new one.... if the issue is not resolved by that, don't be disappointed, in that, you still have a new and reliable carburetor. That and a new EI conversion makes for a good day for me...

$0.02

.

strad
06-23-2013, 02:39 PM
Yes I did think to check the plug wires. They are new (have only a few hours since I replaced them), and they were all tight. The cap is new. The rotor is not new but I inspected when I replaced the cap and it looked ok. The distributor was EI converted by the previous owner. I forget which manufacturer but it is an automotive one.

I have not replaced the fuel filter since I bought the boat in Sept, so that is probably a good thing to do.

I guess the thing to do after the filter is work on the carb. I don't really suspect bad fuel because it hasn't really been sitting in the tank all that long. I burn about 10 gallons per trip, so I'm constantly renewing at least a portion of the tank's contents. I mean I guess it's possible but not as likely as some other causes.


My only real previous experience with a carb issue is my lawnmower carb (thing would run with choke on but not with choke off). Cleaned it up with carb cleaner and it ran great after that. Hope for the same with the boat carb!

edit: well, now I know that the fuel filter is not plugged. I took it out and I can blow through it no problem. It seemed like it was getting too much gas anyways, so a plugged filter was not the first suspect.

SWGA Boater
06-23-2013, 03:11 PM
Same thing was happening to me yesterday. Took the flame arrestor off and noticed gas was dribbling in the secondaries at idle causing the loading up/rough idle. Long story short, a few medium taps on the secondary fuel bowl freed something up and it ran normal in the yard this morning.

Just something else to check...

strad
06-23-2013, 03:30 PM
Well I have an update. Somewhere among the action this morning at the lake, I managed to leave the ignition in the run position (not in start). The coil got hot enough over the last 3 hours that some of that resin they fill them with to isolate different circuits (it's usually black) melted and flowed out of the unit. So the coil is going to get replaced. Obviously fubared.

Anybody have any ideas on why it would get that hot -- ie is it a failure just with the coil or should I be looking further upstream in the electrical system? Never had any issues with it before. . . When it rains it pours I guess!

thatsmrmastercraft
06-23-2013, 04:03 PM
If the electronic ignition was designed to retain the ballast resistor, and the previous owner bypassed or removed it, that could be your problem. Simple check to see is the ballast resistor is there. You could check for a part number on the EI unit and spend a few minuted on the internet figuring out what you have.

strad
06-23-2013, 04:42 PM
Ok. It is a Crane Cams XR700 ignition system. The coil is an MSD Blaster coil. There is a Crane harness provided with the ignition system, and the + wire runs directly from the unit to the coil. There does not appear to be a resistor in line anywhere.

thatsmrmastercraft
06-23-2013, 04:49 PM
Ok. It is a Crane Cams XR700 ignition system. The coil is an MSD Blaster coil. There is a Crane harness provided with the ignition system, and the + wire runs directly from the unit to the coil. There does not appear to be a resistor in line anywhere.

http://www.cranecams.com/uploads/instructions/9000-0700_.pdf

catamount
06-23-2013, 04:56 PM
I'm not sure if cranecams is the same, but on the first first of the Petronix module if you left the key in the run position without the engine running it would burn up coils. On the second version, it sense that the key has been left on and cuts the charge to the coil.

Maybe yours burned up for this reason?

strad
06-23-2013, 05:59 PM
Hopefully! I can work around the key being left on issue. All I need is a functioning brain!

Edit: So it appears that a default installation of the XR700 would require the ballast resistor to stay in place. On a 1984 S and S, where would the stock ballast resistor normally be located? Just so I don't have to look all over creation lol. And if there isn't one, where would you guys suggest I mount one? Obviously in line between the key and the coil on the positive side, but where's a good spot?

edit: nvm. I found it. The previous owners cut the leads off both spade connectors and jumpered the wires together. Grrr. The ballast resistor is still there at least. What should the stock resistance be? My meter is showing 001 ohm resistance.

catamount
06-23-2013, 10:29 PM
.001 is way too low. That's basically no resistance... even my DVOM test leads register higher resistance than that.

Do you have your ohm meter on the lowest setting? Disconnect all leads from the resistor before testing it to be sure that continuity is not finding a way through the coil, etc.

strad
06-23-2013, 11:35 PM
Haha not point 001. 001 as in 1. Sorry for the confusion lol. I ordered another one, because it felt like one of the posts had come loose due to corrosion. The posts both had quite a bit of surface corrosion on them.

strad
06-28-2013, 06:35 PM
Update: Well it was a carb problem. A couple months ago I replaced the fuel intake pipe, and as part of that removed the carb, cleaned the surfaces, and replaced both gaskets. Tightened it down properly too! Between then and now, the nuts backed off/gaskets shrunk. I tightened the nuts again and adjusted the idle screws somewhat. Got it back to a nice idle. Yay! Now a lake test. And I'm smarter than I was this morning lol.

catamount
06-28-2013, 11:10 PM
Glad you figured it out! You mean the base gasket, and the gasket between the carb & throttle plate? Did you happen to shoot those surfaces with carb cleaner when looking for a vac leak? Just curious if they indicated or not.

strad
06-29-2013, 04:55 PM
No I actually did not need to shoot any carb cleaner. I was looking all over, and the aft side of both of those gaskets was moist, either with fuel, oil or a combination thereof. So I knew something was coming out of there. And the slightly loose mounting nuts fits with that diagnosis.

I did run it today for about an hour on the lake. Ran fine, but then when I got back to the dock there was evidence of a vacuum leak again (low idle). I may just replace both of those gaskets and see if that cures it. Maybe they were damaged by having fuel and oil go past them?

thatsmrmastercraft
06-29-2013, 05:49 PM
No I actually did not need to shoot any carb cleaner. I was looking all over, and the aft side of both of those gaskets was moist, either with fuel, oil or a combination thereof. So I knew something was coming out of there. And the slightly loose mounting nuts fits with that diagnosis.

I did run it today for about an hour on the lake. Ran fine, but then when I got back to the dock there was evidence of a vacuum leak again (low idle). I may just replace both of those gaskets and see if that cures it. Maybe they were damaged by having fuel and oil go past them?

Yup, that will do it. While you are at it, replace the nuts that hold the carb in place.

strad
06-29-2013, 10:54 PM
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Yup, that will do it. While you are at it, replace the nuts that hold the carb in place.

Hey I was wondering, are they supposed to be locking nuts? Because the ones on there currently are not. . . Just seems like there's a lot of vibration in this environment and those nuts could use extra help.

thatsmrmastercraft
06-29-2013, 11:59 PM
Hey I was wondering, are they supposed to be locking nuts? Because the ones on there currently are not. . . Just seems like there's a lot of vibration in this environment and those nuts could use extra help.

All I have ever used is lock-washers and regular nuts. I don't see why a person couldn't use nylock nuts though.

strad
06-30-2013, 12:07 AM
Well it didn't have lock washers on it either. Serves me right for assuming the previous owner did it right! No wonder it loosened up lol.