2006 Supra 20ssv assault 325 sputtering problem

I have a 2006 Supra 20ssv inboard with a 325 assault engine and around 250 hours. Mid season last summer I was pulling a rider and crossed another huge wake at speed, almost immediately the boat pops and sputter with half throttle or more, we had to limp back to the dock because the boat would not get on plane . Now ONLY after 2 or so hours on the lake the boat will run bad and we'll have to idle back to the dock. The boat will run perfect, full throttle, pull hard etc while in gear or disengaged. After 2 hours the boat will not rev past 3K while in gear or in neutral, it will fall on its face like its entering limp mode, it will backfire if you keep giving it throttle while its lugging. Oil pressure and temp gauges work and are within spec during the sputtering.

I've replaced the fuel, fuel filter, added stabilizers, isodeet, seafoam, etc, changed and gapped the spark plugs, checked fuel and fuel pressure at the Schrader valve and it was good, looked for exhaust leaks or blockages anywhere in the system, the propeller is good, all throttle linkages are good, there is no distributor cap.


I'm at a loss of what to do. I might try a new fuel pump but I dont think it is the problem. The fule pressure is 60psi constant but I didnt get to check the pressure while it was lugging down unfortunately.

I'm not sure if it is sensor or electrical related due to the original impact, but I know that it is temperature related and most likely fuel related.

Sorry for the long read, I wanted to be thorough on the first post as I have researched this forum and others extensively.

Thanks for any help and input, its greatly appreciated.

P.S. I'll gladly Paypal $20 to whoever can tell me the problem or steer me in the right direction if its not the fuel pump

Getting a fuel pressure reading while it is acting up,,,,, as I think you already know, is going to be key. Obviously since it seemed to start with a big jolt, connections are always suspect, especially at the ecu and fuel pump module (tank connection). The fuel pressure reading would allow you to rule out the pump or connections there to. Not sure where the fuel pump relay lives, but that's another connection worth checking. Unplugging and plugging is usually sufficient to repair a poor connection. Also will make it difficult to know what fixed it if you check a bunch of connections and it stops acting up. Check grounds everywhere you can as well, losing a tenth of a volt through a weak ground is plenty to cause a poor running condition.

Thanks Kevin, I checked everything I could find but I didn't actually unplug and replug the connections so I'll try that. The boat is still in storage but I should have it out in a couple months at the latest and checking the fuel pressure while its acting up is going to be my first priority.

Does anyone think this could be a coil pack issue?

A popping is usually associated with a lean condition. It could be a sporadic crank position sensor which could come and go. Usually you can see a bad crank signal by watching the tach, if it spikes or jumps around while you are experiencing the problem that could be a clue. It wouldn't just follow the engine speed it would jump around quickly. Depends on the tach design if it reacts quickly enough but most newer ones do.

Get it hooked up to the scan tool at your nearest dealer, it will tell you all the fault codes the engine has produced. I had problems yesterday, going into limp mode with a 1000 rpm limit. Scanned it, turns out my oil pressure sender died.

I have an 04 ssv and had similar problems. I was getting 30psi (spec'd) but after an hour or so, it would drop in half with the RPMs dropping around 2k. I put in a new fuel pump and thought that was it. Nope. I pulled the tank and found some trash that may have been clogging the pickup tube but don't know if that was it since it is still sitting in pieces. If that's not it, I'm at a loss. Good luck and let me know what you find out! When I finally get mine together and out on the water I will let you know if it worked.


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Thanks for the info jarodag, I would have thought for sure your problem would have been the fuel pump...

Does anyone know of a cheap scan tool for these indmar assault 325 engines ? Closest dealer is 3 hours away and any reputable shops are 2. Ill probably leave the shop with a 2K bill and the same problem.

"Scan tool", and "Cheap" are never found in the same sentence unfortunately, haha.

Some other things to look at from some google searches of your issues...

1) fuel pressure regulator could be acting up when warm. This would cause normal operation until it gets heat soaked from running, then it could start causing unregulated fuel to increase spikes or not allow enough through. Having a gauge on the shrader valve will be required when it's acting up to get an idea if you're having spikes or drops and when.
2) Potentially vapor lock. I know these boats have had issues with this. Does your problem occur only after you've shut the boat down, then restart? If you went out and ran the boat constantly the whole time, you likely wouldn't experience vapor lock. You WOULD experience vapor lock if you drive a couple hours, shut down the motor for 10-20 minutes or so, then start again and experience the problems then.
3) Bad distributor assembly.
4) Bad ignition module - these can heat up and start sending bad signals if they've gone bad.

Start with the cheap stuff, but there's some ideas.

http://www.rinda.com/acro/prodlist.pdf

They do sell a MEFI 1-4 scan tool for $49. I don't know if your boat is a MEFI 4 or MEFI 5, though. It should be MEFI 4 (which was the standard for Indmar up through 2007, but you'll want to verify the port configuration. The Diacom software package is $579 and includes the scanning capability (but you may need to buy the right cable.)

You can also make your own MEFI code reader by shorting out ECM pins and using a test light. Here are instructions and a list of blink codes. http://www.offshoreonly.com/forums/do-yourself-boating-budget/103342-make-marine-efi-code-tool-less-than-$1-00-a.html

Edit -- Also just remembered that MEFI 4 systems have 2 wire connectors at the ECU, and the MEFI 5 system has 3 wire connectors. Should help you figure out which one you have.

Where is the fuel pressure regulator? Ignition module?


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Originally Posted by jarodag99

Where is the fuel pressure regulator? Ignition module?


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No Idea, those ideas came from a malibu boat with the 340hp indmar. I assume it'll have on though. Look on the fuel rail for something that fuel has to pass through before the shrader valve.

The fuel pressure regulator on that model should be located in the housing that holds the fuel pump. In a v-drive it will face forward and is held by one screw. It looks like this http://www.bakesonline.com/detail.aspx?ID=1650

Heres a couple threads I read last fall to help me Jarod.

https://forum.supraboats.com/showthr...lt-cutting-out

http://www.wakeworld.com/MB/Discus/m...tml?1240182472

It's supposed to snow in TX next week so I guess I wont be testing anytime soon, but my list of possibilities is

1. Fuel pump and or trash in fuel lines
2. Fuel pressure regulator
3. Limp mode due to oil pressure sensor or similar sensor, hopefully the engine is throwing a code if this is the problem
3. Limp mode due to overheating, I checked impeller but Ill go ahead and replace it and try to clean out the raw water heat exchanger thing

Thanks Travis. That's some good info! I will have to check out the heat exchanger too and see if it's clogged. That happened on a friend's Tige. Then it's' servicing the trailer, 2nd battery, LEDs, and swim platform pad next. Quite a few projects before the first outing!

One thing I had to replace when I had rough idling/sputtering engine issues was I replaced the TPS or Throttle Position Sensor. I actually picked one up at Oreilly's for a 1991 K1500 Chevy Blazer and it fixed all my issues. I have seen a lot of other threads that say the same thing. The TPS on the Assault Engines go bad around the same times on the same year models. (I figure it's because most sit through the winter season. Here was some recent info I posted about the TPS:

If you take the TPS off it is spring loaded. When I turned my old one with a screw driver it would stick on the idle side of the spring action. replaced mine and she runs good as new. Nice and easy idle at 800 RPM's. Just make sure that when you put the new one on turn the TPS to the left (or towards the front of the boat counterclockwise) to get it onto the small keyed shaft and then turn the TPS to the right to line up the bolt holes (This will load the spring tension). My throttle body had a small plate under it and I simply bent it down to get the TPS on and then bent it back up to flat gently. Very quick, easy and cheap fix. I got my part from Oreilly's and used one off a 1991 K1500 Chevy Blazer. I have the 5.7 Indmar Assault. Hope this helps you out!

Thanks supraaddict, I thought the tps would be harder to change so Ill probably throw a new one on also. Was your problem constant or only after you've been on the water for a few hours?

I just picked one up at O'Reilly's yesterday and hope to put it on this weekend. It was $40 with the lifetime warranty...$36 without. The issue I had/have (don't know if it's fixed since I haven't had it out since I pulled the fuel tank) was only after being out for a little while. I could go out and ride for a while then go sit at a sandbar and it would fire back up. After about 10mins it would start to bog down on me. Last time it happened I was running pretty low on gas and it happened just as I hit another boat's wake. Pulled the tank and found some plastic in there that probably came from when they drilled the original holes. I'm now waiting on a dealer to find a replacement pickup tube and fittings since mine was stripped as I pulled it out.

Mine was all over the place. When it finally went all the way bad it spit and sputtered all the time and even puffed a little blue smoke because it was running so rough. New TPS and she drops down to about 750 RPM's as soon as you let off the throttle. Purrs like a kitten now! Hope this helps you out!

Same with Supraaddict.
Symptom was high idle coming off plane (1800 +), tap the throttle in neutral would bring down the idle to where it was supposed to be.
Then it wouldn't go under load, just back fire and sputter, unless real easy/smooth on the throttle. Belching black smoke for flooding.
Replaced TPS and good as ever with our symptoms.

Might be a dumb question, but is your 5.7 EFI? I am having similar issues with mine and I have the 325 EFI Assault