Another possibility is the float level. If the float level is too low, you may be draining the float chamber at higher power settings faster than the fuel can refill. Raising either the primary or secondary (or both) float levels might solve this.
Senior Member
Another possibility is the float level. If the float level is too low, you may be draining the float chamber at higher power settings faster than the fuel can refill. Raising either the primary or secondary (or both) float levels might solve this.
Rick Ludtke
1990 Supra Pirata
1987 Supra Comp TS6M
Photo Album https://forum.supraboats.com/album.php?albumid=4
Member
rludtke - Funny you should mention that, I did some more research yesterday which suggested the float level being too low could potentially cause this problem. I'm an absolute beginner when it comes to carburetors. But, I have the manual for it and surely I can figure it out. I should have time tomorrow night to give it a shot. Thanks again for all your help and suggestions.
Unfortunately, the boat mechanic I was referred to is very back up. He has about 50-60 boats in line waiting for attention. So, I'll continue to try and address the issue with the help of this forum and other resources.
Shannon
Senior Member
SVAHLE... ,
Hopefully one of us will find the problem soon . im in the same boat ( no pun intended ) as you . Boat having same syptoms and issues . Thought i narrowed it down to a bad thermastat , but still dropped dead on its face this past sunday ....
Maybe before summers over we will find the lil Gremlin.....good luck and ill keep posting what i try.....think im gonna try to adjust float levels ( as mentioned above )....who knows at this point.....sorta scratching my head because it ran great the first two trips out on the Lake...
Brack
1984 Supra Rider
454 / 1:1 trans
213 Hours !!
" work in progress "
Senior Member
Hi Shannon,Originally Posted by svahle
Float adjustment is actually very easy. Holley.com has tons of technical publications, including "Guidlines for adjusting float level" http://www.holley.com/data/TechServi...Carburetor.pdf
(Ref: http://www.holley.com/TechService/Library.asp)
This exploded view may help:http://www.holley.com/data/TechServi...ed%20View.pdf)
Adjustment is made by bending the float arm small amounts. The instructions provide some target dimensions.
I have also fine tuned my adjustment on the lake. If a stumble exists, I increase the float level until the stumble disapears under hard acceleration load.
Last edited by rludtke; 08-10-2010 at 10:02 PM.
Rick Ludtke
1990 Supra Pirata
1987 Supra Comp TS6M
Photo Album https://forum.supraboats.com/album.php?albumid=4
Member
Here is a little update. I pulled the bowls off the carb last night. Both are very clean. The rear float may be a little low, so I'll raise it a bit tonight (although I don't think this is the problem given its current setting). Although I have limited experience with carb adjustments, everything else looked fine to me.
The last time the boat stalled I was again trying to ski and my girlfriend was driving. She restarted the boat and came around to pick me up. Last night she mentioned that it turned over a little slower than usual on restart. So that caused me to again consider the electrical side of things. After a little research last night, I found a few instances where a weak alternator caused problems similar to mine. The theory being that the alternator is putting out just enough juice to keep the battery charged enough to start the boat. But after running the boat a while at high RPMs the alternator can't keep up, the battery charge gets low, and the ignition system simply can't draw enough volts to function. Or as better explained earlier by rludtke - "As engine RPMs increases, so do the combustion chamber pressures. As the pressure increases, so does the resistance, making it more difficult for the spark to jump the spark plug gap. This is why spark plug testers test spark plugs under pressure. My theory is that your ignition system may be weak." So, I pulled the alternator off last night and had it tested this morning. Sure enough, the output is low. Luckily, I was able to find a new one locally (yes it is a marine alternator). I'll slap it on tonight. Of course a bad coil can cause similar issues, but based on my research, a bad coil usually gets too hot and needs to cool before the motor will restart. Certainly there are other parts of the ignition side that can cause similar problems. But, I've at least tracked down a "bad" part and will start there.
I'm hopeful that the alternator will cure the issue. But, at the same time, I'm perplexed by some of my prior findings such as the fuel pump failing to reprime and lack of fuel in the accelerator pump after stalling on occasion. These problems would be unrelated. I'm a realist and find it a bit to coincidental that there are both fuel and ignition issues. But, I suppose it's possible.
If I can get away from the office a little early I should have time to put the bowls back on the carb, install the new alternator and head to the lake for a test run. If so, I'll certainly report back my results. If the alternator does fix the issue I'll be a little frustrated that I wasted time and money chasing the wrong rabbit for the last several weeks. At the same time, I'll be relieved that the hunt is over, the Gremlin is deservingly dead, and that I can again ski for more than a few minutes at a time. Wish me luck!
EDIT: rludtke, thanks for the links and info on settle the float levels.
Member
And the saga continues.........
I skipped out of work a little early yesterday afternoon to put on the new alternator and raise the secondary float a little. I then took the boat to the lake for a test run. Things were going great and just about the time I was convinced I had the problem fixed, it stalled. I was frustrated to say the least. I took some extra fuel line and a 5 gallon gas can with me. I ran the extra fuel line from the gas can directly to the fuel pump. It ran perfect. That also gave me the chance to see just how quickly this boat will burn through 4 gallons of gas (about 10 minutes at wide open throttle). I then ran off the boats fuel tank again and the problem recurred. At this point I'm running out of daylight and headed back to the boat ramp.
Athough I had looked in the tank twice before and checked the screen on the pickup tube, when I got back to the house, I decided to syphon all the fuel from the tank. I poured the syphoned gas through a funnel with a screen and found some debris. What I found looks like teflon plummer's tape, but its black. I suppose it could be electrical tape that has broken down over time being soak in fuel. There were three or four pieces about 3 inches long or so. I pulled all the fuel I could from the tank. But, I can still see a few very small black pieces of debris in the tank. Hopefully, I was able to remove all the larger, more problematic pieces. I'll be on the water this weekend, so we'll see if this has fixed the problem.
If the problem continues, here are my short term ideas to get me through until winter when I can pull the tank and give it a proper cleaning. I've already began thinking about adding an integrated ballast system that would require rebuilding the rear seat. When I tear into it I could remove and clean out the tank.
(1) I'm wondering if I should remove the screen on the pickup tube and put some sort of an inline screen on the fuel line (between the tank and fuel/water seperator) that is more easily accessible. Then, as the problem occurs I can clean out the inline screen without having to mess with pulling the pickup tube.
(2) I could fabricate some sort of a wire mesh cage around the end of the pickup tube. It would need to be small enough to fit through the hole in the tank for the pick up tube fitting, but large enough that it couldn't be completely obscured by the debris in the tank.
Anyone have any other thoughts or ideas for a short term fix? Thanks.
Shannon
Member
You had your float bowls off and said that they were clean, so the debri is not making it to the bowls, It may be stopped at the water/fuel filter or it may be something big blocking it in the tank.
Do you still have the anti-siphon valve in the tank this sometimes can malfunction and block flow. Also on the pickup is the bottom cut on an angle if not how close to the bottom of the tank does it get. I have seen on some boats the pickup actually suck the bottom of the tank off cutting off fuel flow.
Small pieces would get trapped in a filter, you could intsall a second filter or a sediment trap style that you could see and drain/clean.
Member
There isn't an anit-siphon valve, just a brass 90 degree elbow. The pickup tube is cut at an angle and has a screen on the end. That is where I believe the obstruction is occuring. I've checked the fuel/water separator and don't see any debris in it (at least as far as I can see and I haven't cut it open). This is also a new fuel/water separator as it was replaced early on in this process, but the problem persisted.
Senior Member
How about one of these? http://www.amazon.com/Moeller-Univer.../dp/B000MT94OM
That could cheaply/easily tell you if the problem is in the tank or not, right?
Former owner of a 1987 Supra Saltare. Current owner of a Malibu 23LSV.
Member
I was searching online and came across that same filter. I acquired a little dentist mirror today and I'll try and use it to look around in the tank to see if there is much more debris in there. If it acts up again this weekend I may pick up one of those filters. It would have to mounted in a safe location to keep the glass from breaking and dumping fuel in the bilge! I'd rather find a plastic one of some sort. I'll look more if it comes to that. But, I do appreciate the help.
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