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srh99vlx

VLX surging...suggestions?

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srh99vlx

I recently picked up a '99 Sunsetter VLX with the Indmar Hammerhead with about 500 hrs. I ran the boat at the dealership for 15-20 minutes, it ran smoothly, no issues. I brought it home from Lousiana to Alabama and since I didn't know the history of the boat I was planning to take it to a local inboard boat mechanic to have a complete tune-up. Before taking it in, I wanted to take it to the water for a short run. The boat ran fine for about 10 minutes up to around 30 mph, then I stopped and idled for a few minutes and then I got up to speed and it started to surge and then the RPM's dropped and it shut down. Cranked back up and I took it slow back to the dock. From the dock to the ramp, the boat ran pretty good for about 3-4 minutes around 20 mph and then started surging again. I took it to the boat mechanic for the tune up and he calls me and tells me it is still running rough after a new cap/rotor and plugs, oil, etc. It oscillates about 500 RPM's either way at idle and then also under load. I went and checked it out with him and it ran like a champ on the fake a lake for about 20 minutes. He calls me again today and says the problem has recurred. Anybody had a similar problem? It doesn't happen right off, so I don't think it is bad gas. He is thinking throttle position sensor or maybe even the ECM. He is a good mechanic and knows inboards, but I am going to have to check with him and see if he has the diagnostic computer, if not, I may have to take it to an Indmar dealer if the TPS doesn't work. Suggestions? Similar experiences? Solutions?

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crescentbar
I recently picked up a '99 Sunsetter VLX with the Indmar Hammerhead with about 500 hrs. I ran the boat at the dealership for 15-20 minutes, it ran smoothly, no issues. I brought it home from Lousiana to Alabama and since I didn't know the history of the boat I was planning to take it to a local inboard boat mechanic to have a complete tune-up. Before taking it in, I wanted to take it to the water for a short run. The boat ran fine for about 10 minutes up to around 30 mph, then I stopped and idled for a few minutes and then I got up to speed and it started to surge and then the RPM's dropped and it shut down. Cranked back up and I took it slow back to the dock. From the dock to the ramp, the boat ran pretty good for about 3-4 minutes around 20 mph and then started surging again. I took it to the boat mechanic for the tune up and he calls me and tells me it is still running rough after a new cap/rotor and plugs, oil, etc. It oscillates about 500 RPM's either way at idle and then also under load. I went and checked it out with him and it ran like a champ on the fake a lake for about 20 minutes. He calls me again today and says the problem has recurred. Anybody had a similar problem? It doesn't happen right off, so I don't think it is bad gas. He is thinking throttle position sensor or maybe even the ECM. He is a good mechanic and knows inboards, but I am going to have to check with him and see if he has the diagnostic computer, if not, I may have to take it to an Indmar dealer if the TPS doesn't work. Suggestions? Similar experiences? Solutions?

I had a similar experience with my MasterCraft. (2002). MC had a relay for the fuel pump that went out on me once that caused similar issues with surging etc.

There was also a plug on a wiring harness from the relay to the fuel pump that got wet. I used a water repelling grease in the plug and it ran fine after. Hopefully it's a simple solution.

Welcome to the crew!

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skicrave

Sounds like it's most likely a fuel delivery problem (as alluded to above). I would replace both of the fuel filters as a starting point, and if that doesn't correct the problem get a fuel pressure gauge on the fuel rail to make sure you're getting adequate pressure across the RPM operating range.

I could be wrong, but my understanding is that the TPS is new and was introduced with the drive-by-wire system. Your boat has a mechanical linkage between the hand throttle and the throttle plate, so that probably isn't the issue.

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RTS

Had a similiar surging problem a while back and unfortunately it was the fuel pump. Not a cheap fix, but if you still have the original pump, you are about due for a new one.

Edited by rts

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Madmanacrossthewater
Had a similiar surging problem a while back and unfortuantely it was the fuel pump. Not a cheap fix, but if you still have the original pumpl, you are abou due for a new one.

And/or filter. Pretty common with in that hour range.

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electricjohn

The TPS does not really come into play when running at speed. The computer mainly looks at the MAP sensor and RPMs through the distributor. From those two readings it makes the main parts of its decisions, such as how much gas the engine needs. It sounds like a fuel delivery problem to me....pump or filter. If the engine will not give you a full throttle take off after it starts running rough or act up at higher throttle settings, then I would say definetly to the pump or filter

Edited by electricjohn

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areamike
Had a similiar surging problem a while back and unfortuantely it was the fuel pump. Not a cheap fix, but if you still have the original pumpl, you are abou due for a new one.

And/or filter. Pretty common with in that hour range.

Plus1.gif on the Fuel filter

Also, could be clogged Fuel Injectors. By the way, using a fuel injector cleaner will NOT clear them. You will need to have them professionally cleaned unless you are pretty handy and can do it yourself. I cleaned mine myself and gained 500 rpm. I posted a picture in another topic a while back.

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D-GOOSE
Had a similiar surging problem a while back and unfortuantely it was the fuel pump. Not a cheap fix, but if you still have the original pumpl, you are abou due for a new one.

And/or filter. Pretty common with in that hour range.

agree, start with replacing the filters and I have heard of some Bu's having up to 3 filters but not sure about yours. Also make sure all line's are clean and nothing blocking the inlet.

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D-GOOSE

Is this a carb or PFI eng? Also did the older boats have a anti flow back check valve on top of the tank? I had a boat that had the check ball area full of junk that was picked up from the tank. It would run great at WOT for about 30 sec (carb eng) then would die off. If I kept it under 2500 RPMS it would run great. I rebuilt the carb, replaced the fuel pump and fuel filter all because the eng was starving for fuel. Can't believe I missed some thing so simple at a blocked fuel line.

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skicrave

Hammerhead was always PFI, back then MEFI-2 maybe?

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areamike

I found the other topic I was talking about with Fuel injectors and how to clean them/remove etc..

http://www.themalibucrew.com/forums/index....st&p=199559

Your problem is most likely the fuel filter(s). However, two other things to check would be fuel pressure which would indicate problem with Fuel pump or dirty Injectors. You can have good fuel pressure and still have clogged injectors and that will cause loss of power/rpm/surges etc.

There also may be a screen going to your fuel pump. In the pictures I posted in the other topic, you'll see one part where I indicate a "black thing". IN there is a screen also.

Edited by areamike

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electricjohn

linky no worky

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srh99vlx

Thanks for the replies, hopefully I will be able to meet and talk with my mechanic at length on Tuesday and give him a list of things to try before we start getting into the expensive parts.

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98mallybu

If you've all ready replaced the filter(s) your boat probaly has two, one at the tank and one on the pressure side of the fuel system.

I would put money on Injectors... tell you tech to run the boat with a fuel pressure gauge. take readings at key up, idle, and at 2000 rpms (if he can under load) do a leak down test if the fuel pressure doesn't hold for 5 minutes. (should stay at 40-45 PSI) If it doesn't hold you have a leak somewhere, fuel pump, regulator, or injectors. Easy way to diagnose the injectors leaking is pull the plugs after your key up test under pressure, if one is wet, theres your sign, pull all your injectors and get them bench tested and serviced. If under load the fuel pump is erratic its either the fuel pump or regulator, you can take the regulator off and check for debris in the screen, if there is any debris, replace it. still have the same problem then it's the fuel pump ($300+) or the anti syphon valve at the tank (check ball valve that stops fuel flow if the line is broken)

Highly doubt it's bad fuel or the the TPS, you can tell if it's the TPS in 2 seconds with a diagnostic tool on the ECM... the throttle % will be all over the place when you move the throttle. (i had a bad one on my RLX)

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areamike
If you've all ready replaced the filter(s) your boat probaly has two, one at the tank and one on the pressure side of the fuel system.

I would put money on Injectors... tell you tech to run the boat with a fuel pressure gauge. take readings at key up, idle, and at 2000 rpms (if he can under load) do a leak down test if the fuel pressure doesn't hold for 5 minutes. (should stay at 40-45 PSI) If it doesn't hold you have a leak somewhere, fuel pump, regulator, or injectors. Easy way to diagnose the injectors leaking is pull the plugs after your key up test under pressure, if one is wet, theres your sign, pull all your injectors and get them bench tested and serviced. If under load the fuel pump is erratic its either the fuel pump or regulator, you can take the regulator off and check for debris in the screen, if there is any debris, replace it. still have the same problem then it's the fuel pump ($300+) or the anti syphon valve at the tank (check ball valve that stops fuel flow if the line is broken)

Highly doubt it's bad fuel or the the TPS, you can tell if it's the TPS in 2 seconds with a diagnostic tool on the ECM... the throttle % will be all over the place when you move the throttle. (i had a bad one on my RLX)

I'm pretty sure that even with good fuel pressure, your injectors could still be clogged. Fuel pressure is from the fuel pump not the injectors. Cleaning those injectors is pretty easy actually. You just have to rig up some little power to open them up using a battery then shoot carb cleaner through them, That is what we did and it worked perfectly.

FYI: When I called a mechanic, he was going to charge about 150 dollars just to clean the injectors. I still had to remove them myself, which is really easy.

Edited by areamike

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Surfin247
If you've all ready replaced the filter(s) your boat probaly has two, one at the tank and one on the pressure side of the fuel system.

I would put money on Injectors... tell you tech to run the boat with a fuel pressure gauge. take readings at key up, idle, and at 2000 rpms (if he can under load) do a leak down test if the fuel pressure doesn't hold for 5 minutes. (should stay at 40-45 PSI) If it doesn't hold you have a leak somewhere, fuel pump, regulator, or injectors. Easy way to diagnose the injectors leaking is pull the plugs after your key up test under pressure, if one is wet, theres your sign, pull all your injectors and get them bench tested and serviced. If under load the fuel pump is erratic its either the fuel pump or regulator, you can take the regulator off and check for debris in the screen, if there is any debris, replace it. still have the same problem then it's the fuel pump ($300+) or the anti syphon valve at the tank (check ball valve that stops fuel flow if the line is broken)

Highly doubt it's bad fuel or the the TPS, you can tell if it's the TPS in 2 seconds with a diagnostic tool on the ECM... the throttle % will be all over the place when you move the throttle. (i had a bad one on my RLX)

I'm pretty sure that even with good fuel pressure, your injectors could still be clogged. Fuel pressure is from the fuel pump not the injectors. Cleaning those injectors is pretty easy actually. You just have to rig up some little power to open them up using a battery then shoot carb cleaner through them, That is what we did and it worked perfectly.

FYI: When I called a mechanic, he was going to charge about 150 dollars just to clean the injectors. I still had to remove them myself, which is really easy.

My 1995 Echelon carbed, it was surging ,changed everything, dealer said try K100 gas treatment. 10 mins running with it in no more surging. Try it first before spending big bucks. $7 runs and idles like new. Edited by Surfin247

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srh99vlx

Talked to my mechanic today, still having the same problems. He says it will crank up and runs fine the first time you increase the throttle. Then when you back it back down to idle, it starts to run rough and surges. He has tried the TPS and that wasn't the fix, he said he could unplug the battery for 15 minutes, crank it back up and it runs fine initially, but when backing it back down to idle, it starts again. He is waiting on the correct diagnostic cables currently. I was thinking injectors or bad fuel initially, but why would it run well initially? He is thinking the ECM has been damaged.

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RTS

Fuel pump pressurizing fuel rails before start up, then not being able to keep up once that pressure is used up?

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