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View Full Version : 1981 MC S&S Carb issues I think


tex599
05-03-2012, 11:04 AM
Discussed this in an earlier thread, but decided to start a new one. 1981 S&S with the PCM 351. Boat will run fine for 10 minutes or so and then will stumble and die at higher RPM, 2400 or higher. Has to sit for a minute and will restart, runs fine at low speed under load. No issues at high RPM with no load. Thought it was the fuel pump and replaced it, still having issues. Could it be the carb, don't know when it was last rebuilt.

1redTA
05-03-2012, 11:27 AM
could also be an ignition issue, do you have points? and how is the timing and the advance springs?

tex599
05-03-2012, 11:41 AM
Yes, still have points, not sure how to check timing or points. Did open the distributor and everything looks normal. Any advice

tex599
05-03-2012, 11:42 AM
Not sure where the advance spring is either?

TRBenj
05-03-2012, 12:08 PM
Boat will run fine for 10 minutes or so

No issues at high RPM with no load.

[QUOTE=tex599;835832]then will stumble and die at higher RPM, 2400 or higher.

Your post is very confusing, but I *think* I understand. Please correct me if Im wrong:

1. The boat will run fine under all throttle conditions for a short period of time (<10 min).

2. After running for a short period of time, it will stumble and die above 2400rpm.

Is that right?

I have seen similarly described issues caused by both fuel and ignition. When was the last time you did an ignition tuneup (cap/rotor/points/condensor)? Have you checked for blockages in the fuel system (antisiphon valve, carb inlet filter at the bowl, fuel water separator)?

tex599
05-03-2012, 02:05 PM
TRBenj-you got it right. Last ignition tune up, unknown, I have only owned it for a year. has new looking wires, cap and the underside of the cap, rotor, etc. . . look ok. Fuel Water seperator is good, have not checked carb inlet filter yet. Not sure where the anti-siphon valve is?

TRBenj
05-03-2012, 02:46 PM
The antisiphon valve is usually on the tank. The ones Ive seen are built into the fitting where the 3/8" fuel line attach.

The case that reminds me the most of your symptoms was solved with a new cap and rotor... and the old ones looked "ok". If you dont know how old they are, I would encourage you to replace them with new so you are sure theyre good. If they dont solve your issue, then you'll have a good backup set, if nothing else.

Trying to diagnose an engine in an unknown state of tune can be extremely frustrating.

1redTA
05-03-2012, 03:17 PM
I learned that when trouble shooting engine problems to replace the cheapest things first, they're cheap for a reason

markismm
05-03-2012, 04:34 PM
Might be a fuel delivery problems before the carb. Clogged up fuel uptake line inside the gas tank was my problem with my 84 S&S when this same thing began happening.

tex599
05-05-2012, 10:57 AM
pulled the carb and will rebuild it. Also want to check the ignition coil, anyone know the normal ressitance?

j.mccreight@hotmail.com
05-05-2012, 01:01 PM
pulled the carb and will rebuild it. Also want to check the ignition coil, anyone know the normal ressitance?

1.5 ohm for a coil with an external ballast resistor.

glgisler
05-05-2012, 10:07 PM
Haven't had a problem like this on a boat, but I had a 69 Corvette, and when I first got it, it would run fine, then after awhile, on occasion it would barely go above 20 mph. I would pull off to the side of the road, sit there 10 or 15 minutes, then it would run fine again, until it happened again. It was sporadic, so very hard to troubleshoot. After going through the inlet filters, the carb, and ignition, I finally did what markismm is suggesting to you - I pulled the fuel intake at the gas tank, and the screen was ~ 75% blocked. I cleaned it out, and I never had the problem again. I figured there was some debris of some sort in the tank that would gradually migrate onto the screen and occlude the remaining opening. Let it sit for awhile, it falls away, and car runs OK. Since the screen was so dirty, I flushed the tank out before I reassembled. So, if your carb rebuild doesn't get it..........

thatsmrmastercraft
05-07-2012, 12:13 PM
Anytime you bypass the basics when troubleshooting you end up chasing your tail(spoken from experience). If the points are of unknown vintage, they need to be replaced. They should be replaced every year or two. I would try to find someone to help you get the points replaced and the dwell and timing set first to at least rule this out.

tex599
05-07-2012, 02:24 PM
Thanks, that was my next question, any write ups on setting the dwell and timing?

j.mccreight@hotmail.com
05-07-2012, 08:40 PM
Thanks, that was my next question, any write ups on setting the dwell and timing?

Its easier just to convert it over to an electronic ignition and be done with cleaning and setting points...
Its the best 100 $ you can spend for reliability...

ccowell
05-07-2012, 08:46 PM
No way the boat came with points.. that's what should be left in them. Electronic ignition never did any favors for me.
Its easy to dwell the ignition just get a dwell meter ( I got one for$5) and set it.

TRBenj
05-08-2012, 08:45 AM
Ive got a pile of dead EI modules in the basement... I never found a set of points I couldnt make run. And theyre cheap!

I agree that if you just start replacing parts and rebuilding things without knowing what the cause of the problem was, then youre introducing more variables into the equation and it is much more likely that you will continue to chase your tail.

thatsmrmastercraft
05-08-2012, 09:43 AM
No way the boat came with points.. that's what should be left in them. Electronic ignition never did any favors for me.
Its easy to dwell the ignition just get a dwell meter ( I got one for$5) and set it.

Still driving the 1972 K10 with original points?:rolleyes::D:D

tex599
05-08-2012, 04:46 PM
Pulled the old coil, testing resistance across the two threaded terminals I get 1.8-2.1. Normal resistance should be 1.5 correct? If this is the issue, any of you ever replaced with a generic one from the auto store and if so any particular model/brand?

tex599
05-08-2012, 04:48 PM
Can I buy the points, rotor and cap from autozone or Oreilly's? If so, does anyone happen to know the part numbers.

thatsmrmastercraft
05-08-2012, 05:30 PM
Automotive parts will work for these. I don't know part numbers, but someone on here has Napa part numbers in their signature. Now, if I could only remember who.:confused:

tex599
05-08-2012, 05:37 PM
Found the NAPA parts numbers and went ahead and ordered the condenser, points, rotor, cap and ignition coil

mart_it
05-08-2012, 10:11 PM
Found the NAPA parts numbers and went ahead and ordered the condenser, points, rotor, cap and ignition coil

Would you mind telling us the part #'s for future reference pls? Is this for a 351W?

tex599
05-09-2012, 07:38 PM
Here you go:

1981 351W Pleasure Craft.

Contacts SME 185303
Dist Cap ECH AL129
Dist Rotor AL160
Condenser SME 185338
Ignition Coil-any one will work, that is made for an external resistor, and a resistance of at least 1.5ohm.
They can also order the water pump impeller if you need it.

tex599
05-18-2012, 11:36 AM
The saga continues, after replacing the ignition coil, rotor, cap, points and condenser, we have the same issue. Although it ran great longer than it has in the past, it started cutting out at speed, died and took awhile to restart. Once restarted it idle and would run fine. The only thing left is to rebuild the carb. Does this boat have a fuel strainer in the tank, if so how do I get to it?

thatsmrmastercraft
05-18-2012, 12:53 PM
How about determining if the stall and failure to restart is due to lack or over-supply of fuel or spark. A timing light on the coil wire will show spark. A careful visual inspection for lots of fuel, or lack of fuel while cranking and while working the throttle to test the accelerator pump should get you on track.

cbryan70
05-18-2012, 01:16 PM
Could the spark wires be getting to hot and failing?

TRBenj
05-18-2012, 01:36 PM
The saga continues, after replacing the ignition coil, rotor, cap, points and condenser, we have the same issue. Although it ran great longer than it has in the past, it started cutting out at speed, died and took awhile to restart. Once restarted it idle and would run fine. The only thing left is to rebuild the carb. Does this boat have a fuel strainer in the tank, if so how do I get to it?
The only thing left is to rebuild the carb? :confused:


I have seen similarly described issues caused by both fuel and ignition. When was the last time you did an ignition tuneup (cap/rotor/points/condensor)? Have you checked for blockages in the fuel system (antisiphon valve, carb inlet filter at the bowl, fuel water separator)?

markismm
05-18-2012, 09:43 PM
Again - my thought...

Might be a fuel delivery problems before the carb. Clogged up fuel uptake line inside the gas tank was my problem with my 84 S&S when this same thing began happening.

madcityskier
05-18-2012, 11:54 PM
Had a clog inside the tank years and years ago. Had to remove it and back flush if I recall correctly. That's been 20+ years. I remember that it was something that would get better by filling the tank and sloshing it around in rough water for a while, but soon it would flow back to the fuel pickup.

tex599
05-20-2012, 04:18 PM
So I rebuilt the carb, using a holley kit. Took boat out and ran great for 20 minutes, but would surge like it was not getting enough fuel. This time it would not die and if you pumped the throttle as it was surging it would pick back up. Returned to the dock and let it idle and went back out for another spin ran fine until about 10 minutes into the run, same thing started surging. I am confident this is a fuel delivery problem. What about the secondary fuel bowl and float? Could this be bad?

markismm
05-20-2012, 09:48 PM
Have you considered post #29.

pkskier
05-21-2012, 09:51 AM
Have you replaced the rubber fuel line from the tank to the pump. I had the same problem and this cleared it up.

Lumbergh
05-21-2012, 10:22 AM
Have you replaced the rubber fuel line from the tank to the pump. I had the same problem and this cleared it up.

#2 on skidims top seller list on their front page. Just saying.

http://i470.photobucket.com/albums/rr66/Lumbergh556/DSC01302800x600.jpg

tex599
05-21-2012, 02:04 PM
Yes, replaced the fuel hose the other day. Does anyone know if there is a filter in the tank?

tex599
06-08-2012, 12:49 PM
Just an update, finally got the boat running right again. Still not sure what the issue was, but had to have been fuel related. Rebuilt the carb a second time, and let it soak for a good 24 hours, replaced fuel filter, pulled fuel tank to check for blockage (it was clean), new fuel lines, as well as plugs, wires, condenser, points, rotor and cap. Boat runs great now. Thanks for all of your suggestions.

thatsmrmastercraft
06-08-2012, 01:25 PM
Sometimes you never do find the cause. Always thankful for the fix though.

MasterKraftS&S
06-08-2012, 01:49 PM
I'm having problems with the Ballast Resistor going bad in my '84. Presents like a fuel/carb problem as described in THIS post but ya bypass the resistor and she runs like a champ! Recently installed coil(w/Built-in resistor) left bypass on and the coil worked for literally 3-5mins and then NO spark.

Put the old coil back on and she runs. Any ideas why the resistors keep failing? Does Elec. Ignition make ALL these problems go away? Did my OLD school mechanic give me the WRONG coil?

tex599
06-08-2012, 02:34 PM
Not 100% sure what the resistor does, but I do know there are 2 types of coils, those that need external resistance and those that do not. Not sure if can switch one out for the other, without changing other things. I would go back to the original coil, using the external resistor. You can get the coil at Napa or O'Reilly's. If you do switch to electronic ignition, most of the instructions have you bypass the resistor, but you are also putting in a new coil.

Are you sure that the coil is what is failing? Have you verified no spark at the coil? How do your points look, when was the last time they were replaced? Having just gone through this I would go ahead and change the points, condenser, rotor and cap. New spark plugs, mine where a year old and the gap was way off. Makes a huge difference in the idle and startup. Set your dwell and timing and go from there.

SilviaMan
06-08-2012, 03:27 PM
The resistor reduces the voltage at the coil to prolong the life of the points and coil.
The "old school" coils can handle straight battery voltage for a short time.
I imagine that the ballast resistor could be opening after it gets warm.
when you have the no start / problem does the coil have power while cranking? does the ballast resistor have power in but not out?

MasterKraftS&S
06-08-2012, 03:57 PM
The NEW coil(w/resistor) started fine but died before we ever got up on plane. No spark was coming from coil at that point.(Put old coil(no resistor) back in) I never checked the resistor as I had the bypass in since last week(and we ran her HARD with an all day barefoot clinic). SilviaM - I'll reconnect resistor and check - power in/out - COLD and then HOT(when symptoms present). It's less than a yr since we replaced R, P,P, and Cond. and we have a brand new Holley 4160 and fuel supply line(i believe)

tex599
06-09-2012, 12:31 AM
You can check the resistance in the coil, it should read 1.5ohms if good. I think all you have to have at the coil to spark is voltage, good resistor, and a good ground. From there it goes to the points and condenser.

cptskier15
07-20-2012, 08:54 AM
There is a filter in the pick up in the tank, we also found that when we had this issue that the rotor arm and cap was not 100%. replace those bad boys!