Old boat help

[LFADAM]

Our club bought a 1990 Supra Sunsport in March. When we test drove it, it ran great (go figure). For the couple weeks after it ran great too. Then it started to go downhill. It hesitates under acceleration and eventually surges from 2000 to 3000 rpm, no in between. Itll run terrible then get over 3000 rpm and run fine again. The problem gets worse the longer you run the boat. Eventually it will hesitate longer and longer to the point where it wont get above 2000 rpm and just stay stuck at a half plane under full throttle bogged down. Also the idle gets worse and worse the longer you run it until it surges more and more at idle and eventually starts stalling.

First we tried a carburator cleaner and sea foam. That didnt work. Then we tried rebuilding the carb. That didnt work. Then I took it to a shop where they pumped out 4-5 gallons of water and redid the totally rusted points, that HAS to have fixed it right? Nope. Still exact same problem. We have replaced the fuel filter twice. The vent line on the tank isnt clogged. What the heck could it be?! The boat was old and sat for a couple years, which is not good...but it ran fine at first. And we have put gas in the boat a few times, so its not old gas.

We NEED this boat fixed for our club to ride and we dont have unlimited money to throw at it so I need to find the cause of the problem. Ive talked to 2 mechanics and both cant figure it out. Someone on the these forums has to know something, please help us out!

[pet575]

Have you verified that the fuel pump is working correctly?

Moving in a different direction, how do you know this is a fuel/carb issue and not still electrical? I've seen a coil that is bad that will not really act up until the engine temperature heats up the coil.

What do you mean by "redid the totally rusted points"? Did you replace them or file them? Did you re-gap them?

[LaynDoor]

Heres my guess... could be wrong, I hope I am for your sake...

How long did it sit exactly? Sounds like the old gas turned to varnish... flakes off the inside of the lines/tank and clogs up the works (like plaque in an artery)... when you shut the boat down it settles again... I had a Johnson outboard that would do the same thing... had a chunk somewhere in the fuel system that would bounce around... Except it would eventualy shut down completely and wouldnt start again for hours.

Im afraid I know of no easy way to remove it... other than cleaning / changing out the tank and lines.

[LFADAM]

pet575, what would you recommend to verify the fuel pump? I feel like if it wasnt working correctly it would be more random/not be heat dependent (longer it runs the worse it gets). And Ill have to check what the mechanic did exactly with the points. I would guess they filed and re gapped them but Ill check.

LaynDoor, a few years. And thats one thing we have been thinking...some kind of debris in the gas tank. How hard (or expensive) is it to remove and clean the tank? The tank seems pretty easy to access (its under the sundeck in the back of the boat)

Thanks

[FlyZone CR]

It sounds kind of similar to a problem I've been having lately. First start of the day is perfect, fires right up. As the engine gets hotter it starts running worse and worse, what you especially notice upon take-off. The problem and bogging gets worse and worse until the engine stalls.
In my case it's water/humidity inside the distributor cap. I open it, clean/dry it, put it back on and I'm good for the rest of the day.

Something you might want to check (if you haven't yet), but in any case: go over to www.correctcraftfan.com's forum and post your issue there. I know a Supra is not a CC but they'll help you out nevertheless. Good people and amaaaazing amounts of knowledge there.
Good luck!

[Okie Boarder]

I think a few of the ideas are good ones. I would suspect the electrical issue or the debris issue. I would second what FlyZone has said about ccf...great guys and lots of knowledge over there. The tank is pretty easy to get out. Remove the rear seat and the ski locker and you'll have full access to get it out.

[Hollywood]

So it starts and runs OK cold? Who rebuilt the carb and what exactly did and didn't they replace? Have you verified fuel pressure?

Take the flame arrestor off and make sure the choke is opening up all the way as it warms up. This takes a few minutes to reach operating temperature. This would be the simplest and easiest fix.

Go over the ignition system and make sure you have the proper coil. If you're still running points though I wouldn't suspect this has been tampered with. What others are describing is the common ballast resistor bypass w/o replacing the stock coil with one having larger resistance (to make up for the external resistor) during an Electric Ignition conversion. This results in too much current through the coil and eventually burning it up.

You can run the engine off a 3' hose from the pump directly into a gas can to eliminate the rest of the fuel system but this shouldn't necessarily be temperature dependant though. A clean carb is just going to get clogged up if the crap is coming from upstream.

BTW - 1990 is not old!

[LFADAM]

ITS FIXED!

Turns out after the marina sucked the water out of the gas tank and redid the points that it was basically fixed. The problem was when I took it out after that, there was probably 1 gallon of gas in it. Since its nearly impossible to get all water out of the tank without draining and cleaning it, Im guessing some water managed to get in again causing the same problems. After adding 30 gallons of gas to the boat it ran flawlessly last night and again today. Not 1 stalling, no hesitation/bogging down. Even ran about 800 lbs of ballast.

Knock on wood that was all...I dont want to jinx it but right now its running great overall. Maybe itll act up again when the gas gets too low but Im beyond relieved/pumped.

[Nor*Cal]

Always store it with a full tank and add a fuel-water separator (if there isn't already installed).