88 Sn2001
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=41651
Printed Date: May-02-2024 at 3:57am
Topic: 88 Sn2001
Posted By: lonestar
Subject: 88 Sn2001
Date Posted: August-01-2017 at 9:35am
Here's what I have going on. 88 SN2001, 351w with 500 hours on the boat and motor. It has a new petronix and flame thrower coil as of mid summer last year. New carb as of last season. I service the boat every year with all of the basics, oil, fuel filter etc so it's pretty well cared for. This year I had a mechanic check and set my timing and firing order to get it corrected after somehow I screwed something up installing the petronix last year. Once that was completed I'm told the boat was running great but I never had the chance to test it myself. However my brother in law decided to drop 5 gallons of really really bad gas in the tank and when I go to use it with the kids and friends 4th of July it's running like garbage. I proceed to run 15 gallons of fresh super through it , 10 gallons of 100ll aviation fuel , seafoam, dry gas, STP, you name it I've put it in the tank. I've also run the tank dry out on the water and refilled so I know the fuel in the tank is now good. I removed the carb and had it ultra sonic cleaned .
Here's what it's doing . At the dock in idle it runs smooth, I can rev the motor as high as I want and it sounds pretty good. Leaving the dock in reverse it's a little pinky and feels like it wants to shut down but never does. Once on the water I hit the throttle to full I can only get about 1000 rpm and it just plugs along. After 30 seconds to a minute it jumps up to 2000 rpm and stays there bouncing intermittently to 2100 or 2200 rpm for half a second. If I pull the power back and hit it again the whole process starts all over again. If I run it like that for say a half an hour or so now and then it comes to life for just a millisecond and jumps to 3000 rpm .
So even after the carb being cleaned I'm still in the same spot I was. I've had good engine guys tell me it's gotta be a carb issue and others tell me it's gotta be a firing order issue.
I don't know ? I'm just trying to get going in the right direction here. Should I replace the fuel pump and rule that out ? It it possible those can get plugged up and not supply enough fuel ?
Thanks in advance for any assistance.
Chris.
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lonestar
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Replies:
Posted By: Dreaming
Date Posted: August-01-2017 at 3:50pm
88 SN should have a mechanical fuel pump. I don't think that is the issue unless you have low fuel pressure. Running crappy gas through your system is a problem... the fuel filter and carb will catch any small debris that is in the old bad gas, and the magic bottles of stuff, 100LL etc. aren't going to fix that . Draining the tank and cleaning out is your best bet, even if you need to pull it out of the boat. then replacing the fuel filter, blowing out the fuel lines ( or replace if they are old) , and then doing another carb clean/rebuild as the carb could have new junk in it from filter overflow, blow it out with compressed air (all orifices) if your gaskets are the blue kind, they are re-usable. if not, Carb kits are cheap and this is a 1-2 evening project if you are mechanically inclined. once you are back at a baseline, you can adjust the mixture screws with a vacuum guage for your idle etc. it sounds to me like you need to focus on the secondary fuel delivery side though. I would adjust the primary side for vacuum though, you could be too rich or too lean and having a hard time getting the engine to transition from primary to secondary circuits.
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Posted By: backfoot100
Date Posted: August-01-2017 at 4:11pm
Sorry Chris but I'm going to play devils advocate here which you may not appreciate.
You installed a new carb and a new EI conversion and went completely on someone else's say so that it was running great without a water test yourself? Let me guess, that someone else was the mechanic? Did he actually take it out for a water test or just run it on the trailer without a load? You admit that it runs great at the dock in neutral and unloaded. I can only assume a water test was never done.
We need more information to help you out....like why did you replace the carb and put in the Pertronix in the first place? Did you have some issues beforehand you thought a new carb and EI would miraculously fix? We see this exact same scenario on here time and time again. Then you admittedly screwed something up when installing the Pertronix and had to take it to a mechanic.
This is by far the most important question we need answered.......Has this boat ever run good since these items were installed based on a real water test by you vs. what someone said?
If that boat was never tuned on the water under a load after installing those parts, there are multitudes of problems that can crop up as you're finding out.
Stop blaming your BIL for dumping really, really bad gas in the tank. We need to get to the root cause and effect before blaming the gas and throwing more parts at it. This is one of those rare instances when TMI is way better then not enough.
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When people run down to the lake to see what's making that noise, you've succeeded.
Eddie
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Posted By: MourningWood
Date Posted: August-01-2017 at 6:22pm
The firing order is the most simple to correct (if that's part of the problem).
Does not sound like a fuel pump issue to me either.
Make sure the coil is of the correct resistance to mate with the Pertronix, and be sure the "mechanic" bypassed the ceramic ballast resistor.
Then I'd check for a vacuum leak. Possible the carb base gaskets.
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Posted By: lonestar
Date Posted: August-01-2017 at 10:51pm
All fair questions.
The carb was replaced last year because the original was due for a rebuild. A rebuild here where I am was going to cost around $550.00 and a new one from skidim at the time was about the same.
The new petronix was my own idea. I had one in the boat that we installed about 5 years ago. I simply got to thinking that rather than wait for that one to go bad it may be a good idea to replace it and keep the old one as a back up. Additionally the original coil was fine to, skidim recommended the two as a pair so I went with it. The water test was done by the mechanic I used and he thought it was great. My brother in law who has ran the boat for the last almost 30 years since new took it to the course and skied off it and all was great.
No the boat was not tuned on the water under load.
The 5 gallons of gas the were accidentally dropped in I can assure you was not pretty I saw it early in the season and hid it to be disposed of but unfortunately was found and used.
The filter was changed pre carb cleaning. So twice this season, once before it hit the water and enforce the newly cleaned carb was reinstalled.
On the new petronix install last year I had a wire that was broken and I missed that caused me a lot of grief . Not realizing a wire was broke I started to play around with the timing
thinking that was the problem mistakenly.
Since the new items were installed and the wire isssue was found and corrected yes the boat ran well. Prior to the broken wire being identified I burnt up 2 caps and rotors.
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lonestar
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Posted By: lonestar
Date Posted: August-01-2017 at 10:53pm
Thanks, good ideas. Ya I've had a couple people mention checking vacuum .
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lonestar
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