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Old     (hawk22)      Join Date: Jul 2006       05-18-2012, 12:30 PM Reply   
So we were out on the lake this morning on the boat starts perfect and runs perfect for about the first hour. Then it starts being difficult from whole shot...most of the time it will die if you just throttle it too much. But if you can ease into it, it will run perfect. Idle is fine. The initial first cruiser gear is fine. But when you try to get on it, it doesn't go. There was some fuel smell associated with it so it seems like it is getting too much fuel possibly. And the symptoms seem like almost a flooding issue. I am not very mechanical, but what are some steps I can take to troubleshoot? Any help would be greatly appreciated.

FYI, we had this problem last week and assumed it was a plug. Found one that had a fair bit of carbon build up on it, so we cleaned it up. After that we fired up at home and was seemingly running well.

info: 2003 Supra Launch SSV, Indmar Assault MPI 320 5.7
Old     (sippi)      Join Date: Dec 2007       05-18-2012, 12:33 PM Reply   
i've never heard of "too much fuel"... but to me it sounds like either fuel filter or fuel pump... i'd go with filter if i had to take a guess.. plus if you replace them and its still doing it you'll want to have your fuel pump looked at ... my money is on fuel filter though. i don't know if you're boat has two or not, someone else will chime in on that one. they are an easy fix and pretty cheap so try that first.
Old     (kmayotte)      Join Date: Aug 2010       05-18-2012, 12:37 PM Reply   
I had water in my tank last week that was causing all kinds go issues, somewhat similar to yours. Could be that.

See my full explanation and fix here
Old    9Drozd            05-18-2012, 10:26 PM Reply   
Just fixed a customers boat today that had the same issues. Bogged down at high rpms and run fine at low rpms. Fuel filter and water separator were both fine. New plugs and double checked the timing. Long story short it was the anti siphon valve on the fuel tank sticking open. I learned something new today.
Old     (tx_foilhead)      Join Date: Apr 2009       05-19-2012, 5:09 AM Reply   
Does it keep running or get worse once it starts to happen? Do you put it up or just keep going? If you take it out when the issues start you might want to look into the ignition, I've had the distributor module go bad and a a bad coil that did cause similar issues, ran great for a while then once everything heater up things would start going south. The coil would get too hot to touch and eventually would go out completely.
Old     (hawk22)      Join Date: Jul 2006       06-01-2012, 11:35 PM Reply
Old     (hawk22)      Join Date: Jul 2006       06-01-2012, 11:40 PM Reply   
Well, I'm kinda stuck here. Any other suggestions. New plugs,cap, and rotor. Sorry I don't know how to embed the video, but if you watch you will see the dark dark smoke and then at at about the :21 mark you will see lots of black coming out of the exhaust. It is still giving signs of flooding. Idles great. Once you get it above 2000 ish RPMs seems fine. But just getn on it from idle to the higher rpms is a struggle.
Old     (tomcat22)      Join Date: Jun 2007       06-02-2012, 7:22 AM Reply   
I have an 04 supra and mine did about the same thing last year and ended up being my fuel pump. I would get it checked along with replacing fuel filter.
Old     (hawk22)      Join Date: Jul 2006       06-03-2012, 11:52 AM Reply   
I was told the fuel pump wouldn't be an issue for too much fuel. I just changed the filter last season, but I will change that again. Is there a way to tell of the injectors need replaced?
Old     (hawk22)      Join Date: Jul 2006       06-06-2012, 11:37 PM Reply   
Anybody ever changed or tested Throttle Position Sensor (TPS)? I was told to check that as well.
Old     (Elliottsx80)      Join Date: Feb 2012       06-07-2012, 8:15 AM Reply   
i dont think that would be your prob. if the tps is messing up you usually have a dead spot in you tp that is not picking up. i would get a fuel pressure gauge and check your fuel pressure first. should be a shrader valve on your fuil rail. if you have good pressure i would lean more towards a map sensor or something like that. have you pulled the cap and rotor to make sure there is no condensation or cracks?
Old     (hawk22)      Join Date: Jul 2006       06-07-2012, 12:34 PM Reply   
cap, rotor, and plugs all new
Old     (CarFanatic5)      Join Date: Apr 2010       06-07-2012, 2:04 PM Reply   
that very well could be a TPS sensor, or Mass Air Flow Sensor.
Old     (hawk22)      Join Date: Jul 2006       06-08-2012, 1:22 PM Reply   
anybody know where either the mass air flow sensor or throttle position sensor is located? I may just pull them out and replace if its simple enough...
Old     (boardjnky4)      Join Date: Dec 2011       06-08-2012, 1:40 PM Reply   
throttle position sensor is on the throttle body. MAF sensor should be somewhere between the air filter and the throttle body.
Old     (CarFanatic5)      Join Date: Apr 2010       06-08-2012, 1:57 PM Reply   
I would try cleaning the mas air flow first.. if they get to oily or dirty they can do a false reading. Spray some electrical or break cleaner on it.
Old     (rallyart)      Join Date: Nov 2006       06-08-2012, 5:40 PM Reply   
Does Indmar use a mass air flow sensor? Most GM's use a Manifold Air Pressure sensor and an Intake Air Temperature sensor instead. I don't know.
If you have one carboned plug on an MPI boat I would run injector cleaner through it. Sometimes an injector can get sticky and not react as fast as it should or leak fuel and make that cylinder run rich.

Last edited by rallyart; 06-08-2012 at 5:42 PM.
Old     (hawk22)      Join Date: Jul 2006       06-09-2012, 12:15 PM Reply   
changed fuel filter. emptied the old one into glass jar and no signs of water or anything else. A tinytiny bit of sediment, but nothing notable. Checked fuel pressure with gauge. 40 to start. Throttled dropped to about 35 then back up to 40. Cleaned MAP sensor. Ran seafoam through. No change in behavior. rrrr. where are the vacuum lines that someone mentioned to check
Old     (hawk22)      Join Date: Jul 2006       06-10-2012, 8:23 PM Reply   
Can someone tell me what this is? is this a vacuum line? or fuel return? Just noticed it had a crack, but it appears to just be painted and the paint is cracking. The rubberish tube seems fine, but just curious if this is anything I am potentially supposed to be checking...
Attached Images
Old     (hawk22)      Join Date: Jul 2006       06-10-2012, 8:24 PM Reply   
the top hat looking thing with the spark plug looking wire coming off the top
Old     (CarFanatic5)      Join Date: Apr 2010       06-11-2012, 6:39 AM Reply   
that looks like your fuel pressure regulator. The rubber line should be a vacume line
Old     (Elliottsx80)      Join Date: Feb 2012       06-11-2012, 7:26 AM Reply   
thats exactly what that is. if you pull the vacume line off and fuel comes out of the vacume line its no good. huge problem with gm 99-02 silverado trucks.
Old     (CarFanatic5)      Join Date: Apr 2010       06-11-2012, 7:37 AM Reply   
ya fuel should not come out of the line.
Old     (hawk22)      Join Date: Jul 2006       06-13-2012, 12:24 PM Reply   
@ thomas, where is the anti siphon valve? I may check that cuz all else has led to no change in behavior. I do have MAP and TPS on the way, hoping one of them will solve the issue. Summer is here....well, kinda...its ridin season anyhow
Old    9Drozd            06-13-2012, 5:01 PM Reply   
Usually its on the fitting on the fuel line coming out of the tank. It has a little ball check valve in it. You will probably have to pull up your center floor board to get to it. Its there in case the fuel line comes loose or gets a hole in it, it keeps the bilge of your boat from filling up with gas. After I posted that I realized yours is fuel injected so i'm not too positive that it will solve your problem. The customers boat that had the problem had a carb and a mechanical fuel pump.
Old     (hawk22)      Join Date: Jul 2006       07-09-2012, 9:32 AM Reply   
Well, I was out of option so finally decided to take it into the shop. They let me know that the internal fuel pump was failing. I was told on supra forums to check fuel pressure to make the sure the pump is working and it held steady 35-40. The shop told me that the pump that supplies the injectors needs to run closer to 60. And evidently it is buried inside the fuel housing so it is quite laborsome. So I finally got to pick up my boat on Friday, dropped a little over a grand for the labor and part. Put the boat on the water Sunday....and...the problem still exists! So frustrated! Never fun dropping that kind of money, but especially when it does nothing.... Sorry, venting! Waiting to hear from the shop this morning...
Old     (CarFanatic5)      Join Date: Apr 2010       07-09-2012, 9:38 AM Reply   
ah.. man that sucks..
Old     (hawk22)      Join Date: Jul 2006       08-02-2012, 10:48 AM Reply   
Well, the shop was wrong. They thought pressure needed to be 60, that is why they replaced the pump because it was only at 35. They have since admitted it actually only needed to be 35-45, so it was on the low end and needed replaced anyway. $1100 later, my shop sucks! Boat still doesn't run. And they have no idea how to fix it. Any mechanical geniuses here?
Old     (yjwrangler95)      Join Date: Oct 2011       08-02-2012, 11:06 AM Reply   
This might be a dumb question, but can you check to see if you have any codes? OBDII?
Old     (hawk22)      Join Date: Jul 2006       08-02-2012, 12:01 PM Reply   
Yeah, sorry, I didn't include the whole shop rundown, but that was all performed at the shop. They got no error codes at all. I took it back after they "fixed it" with the new fuel pump and told them it wasn't fixed. So then they supposedly were in conversation with Indmar and they flashed my computer to make sure it was set to the proper settings. They performed noid tests to the injectors. (none of this was part of the 1100 I spent, so cautiously awaiting another large bill) They say the computer seems fine, but they think I new one will fix the problem???? What kind of sense does that make? I've even been talking with Larry at Indmar and he doesn't seem to think its the computer, yet my shop wants me to drop another 1400 to change the computer and hope it works even thought mine seems fine...
Old     (hawk22)      Join Date: Jul 2006       08-02-2012, 12:04 PM Reply   
If they said 1400 for a new computer and it will work...different story. I say fix it. But refund me the money for the unnecessary fuel pump first. But they don't even feel confident it will work. They tell me mine checks out fine, but a new one might fix it... Boggles my mind that a shop thinks thats okay business....1400 for a "might fix it"....
Old     (bmock50)      Join Date: Feb 2011       08-02-2012, 12:07 PM Reply   
Black smoke and fuel smell means its running rich. I had the same problem except my problem was with the carburetor/choke linkage, don't know what would cause it with efi.
Old     (jbird)      Join Date: Jun 2011       08-02-2012, 12:11 PM Reply   
IAC valve need replaced/cleaned? How does your oil look? Not those, I'd look into your ECM for codes or malfunction...
Old     (Truekaotik)      Join Date: Jun 2012       08-02-2012, 12:37 PM Reply   
Ok, a sensor would throw a code so that's out.. You'll have two new sensors to sell... After all the posts I've read, it seems IAC or TPS would of been the first look, I'm surprised Jbird was the first to recommend... the IAC controls the air/fuel flow.... Especially having the problem off idle only... If its not the IAC.. My next check would be a injector hanging open, but that would most likely be intermittent? Plus you said they tested them.. Hmmm I'm just tryin to come up with something other than computer... Which it "may" be, but who wants to spend 1400 after just spending 1100 or so... Especially when it's not confirmed... Umm, you mentioned new rotor, cap, plugs, Fuel filter, pump. TPS has been checked or replaced as well?.. Check IAC... I may post again, after I run a check on the motor your talking about, to see if I can come up with something else..

Last edited by Truekaotik; 08-02-2012 at 12:42 PM.
Old     (hawk22)      Join Date: Jul 2006       08-02-2012, 1:25 PM Reply   
yeah, changed the tps. It didn't change the behavior so I changed it back. Where is this IAC? And wouldn't that create an error code in the diacom if it was an isssue?
Old     (Truekaotik)      Join Date: Jun 2012       08-02-2012, 5:42 PM Reply   
It should, yes.. Dang... Umm try to check your return fuel line to see if it's kinked somewhere.. If its kinked a tiny bit, this may be a issue... Because at high flow it doesn't let the fuel return to the tank... It's attached to the fuel rail and returns to the tank...
Old     (jbird)      Join Date: Jun 2011       08-02-2012, 6:14 PM Reply   
Of the stories I've heard about bad/dirty IAC's...No, they didn't mention throwing codes!
Old     (Truekaotik)      Join Date: Jun 2012       08-02-2012, 7:12 PM Reply   
Sweet!^^^ see Jbird thinks you should still check it.. On my scorpion it beeps on me...
Old     (hawk22)      Join Date: Jul 2006       08-02-2012, 7:37 PM Reply   
is the IAC not the same as the MAP? Or am I thinking of something else?
Old     (greg2)      Join Date: May 2002       08-03-2012, 3:41 PM Reply   
I would check the fuel pressure regulator. I had one go bad on an older f 150 and it was running VERY rich. It ran great as long as you had your foot in the gas, but did not idle well.
Old     (hawk22)      Join Date: Jul 2006       08-03-2012, 4:08 PM Reply   
Thanks Greg that's my next step. I just got of the phone with Bakes Marine and that's what they suggested. Per others on here, I pulled the vac line off the top to see if fuel came out. None did. So I assumed it was good, but is there another way to test the regulator? Is it easy to pull apart? Someone mentioned it has a screen inside that may need cleaned.
Old     (hawk22)      Join Date: Jul 2006       08-05-2012, 10:43 PM Reply   
Any other way to check the regulator beside fuel coming out of the vac line? I am going out to check it at the lake under load tomorrow. Also does it just pull apart, I hear there is a screen there too?
Old     (hawk22)      Join Date: Jul 2006       08-10-2012, 7:27 PM Reply   
Well, I finally decided to take it into the dealer 2 hours away from me...hoping they would have better luck/info than my local shop. Got a call today, they can't figure it out either... They tell me by all tests and measures, the boat should run perfect. Except it doesn't, they just can't figure out why it doesn't... so I've stumped 2 certified indmar shops. I guess that gives me hope for future problems that my buddy and I can troubleshoot most of the things the shops would've done. The problem is Summer is just about over and my boat still sucks.
Old     (TrentAllman1)      Join Date: Aug 2012       08-24-2012, 4:09 PM Reply   
I have a 97 Tige inboard with a 350 Chevy w/ Holley carb, but strangely had almost an identical experience run for an hour, cut off and then run at 1000 but cut off if you tried to go to 1100. Cut it off for a minute and it runs fine for 15 minutes then repeats the cutting off, not able to increase speed. I had been having problems for two or three years and had torn down the carb several times, sometimes finding trash sometimes not. This time I was determined to get it fixed, so I pulled out the tank which was a 32 gallon Aluminum and upon dumping the last 4 gallons into a white bucket I found many rust particles. There were even more in the tank that I had to vacuum out. My theory is that there was so much rust it would block off the intake mesh, but release when there was no suction. Although the tank was aluminum they used a steel plug and double tapped bushing that were covered in rust. I am in the process of replacing those with brass right now and have not gotten the tank back in the boat yet to test my theory. However it would have to be better without the rust in the tank, check your tank. Contact me if you need any more information.

Possibly it is related to ethanol in the gas but I can't really say so, I found no water at all in the gas.
here is an article that was in our paper about the dangers of ethanol in boat gas.
Old     (illini88)      Join Date: Oct 2007       08-24-2012, 5:25 PM Reply   
Have you tried draining the tank and going fresh gas? On my old Tige, I had to run a fuel addative every couple tanks of gas. The thing would just start losing power. I'd add some fuel treatment, and it would be just fine. I assume there was something in the tank on that boat, but cant be sure.
Old     (denystaucd)      Join Date: Feb 2003       08-24-2012, 6:41 PM Reply   
Hopefully you got this fixed??? But I'd step back; test compression and then take off that u pipe exhaust off from under the swim deck and see if it's blowing smoke the same on both banks of the engine. The other big thing to check is the exhaust tubes themselves. Those rubbery ones from the exhaust manifold to the stern bulkhead. I've seen them come apart inside and cause to much exhaust back pressure.

Old     (TrentAllman1)      Join Date: Aug 2012       08-25-2012, 7:40 PM Reply   
To fully clean a tank you have to take it out of the boat, get all the gas out, dry it out, and set it at an angle and tap the bottom. I had to use a pvc pipe duct taped to a shop vac and then kept lifting and tapping the tank from one end to another to get the rust to pass by the pipe. After 15 min I got 99% of the rust out that way. Just draining it won't do any good. I can send pics or video of how to do this as my tank is still out as the pipe taps I've ordered have not come in yet. If nothing else you can eliminate the tank from being the problem with no costs but your own labor. Of course be safe when handing or removing the gas.
Old     (hawk22)      Join Date: Jul 2006       09-03-2012, 5:31 PM Reply   
unfortunately not fixed yet. I don't think it is tank related. The 2nd shop that had my boat used their own fuel and same problems occurred. I could check the exhaust tube easy enough I'll try to do that next time out. oddly enough, I put aanother can of seafoam in there and it ran quite a bit better more consistently, but the problem is still there it just happens a little less it seems. Noticed quite a bit of black smoke today while we were out. And the my hull turning black so there is definitely too much fuel somewhere


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