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1998 Sea Doo GSX Limited - 12V Low

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Water Crafts
1998 Sea Doo GSX Limited
#1
So if it’s showing that my volatage regulator/rectifier is bad via the 12V Low blinking on the dash... does that mean i have to buy a whole new MPEM for the machine. If it helps the key doesn’t beep when it is put in either
 


JeremyD615

Well-Known Member
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Location
Nashville, TN
Water Crafts
1995 Sea Doo Speedster
1995 Sea Doo XP
1996 Sea Doo XP
#2
General tech questions should be posted on the regular 2-stroke forum. You’ll have much more exposure there...

The light on the gauge is for low voltage, not the regulator/rectifier. You most likely just have a bad battery. Try a new fully charged one and I’d be willing to bet the problem goes away.
 

JeremyD615

Well-Known Member
Messages
483
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53
Location
Nashville, TN
Water Crafts
1995 Sea Doo Speedster
1995 Sea Doo XP
1996 Sea Doo XP
#7
The first thing to do is put a volt meter on the battery and see what the voltage is in a static state. Then crank the motor and note what the voltage drops to while cranking. Once it starts, write down the voltage at idle and at 4-5000rpm. Reply with what all of those voltages are and we can help from there.
 
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Water Crafts
1998 Sea Doo GSX Limited
#8
The first thing to do is put a volt meter on the battery and see what the voltage is in a static state. Then crank the motor and note what the voltage drops to while cranking. Once it starts, write down the voltage at idle and at 4-5000rpm. Reply with what all of those voltages are and we can help from there.
I’m busy tomorrow but I’ll do that tomorrow and report back
 

Chester

Premium Member
Premium Member
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Location
Langley, BC Canada
Water Crafts
98 SXi Pro
#10
The first thing to do is put a volt meter on the battery and see what the voltage is in a static state. Then crank the motor and note what the voltage drops to while cranking. Once it starts, write down the voltage at idle and at 4-5000rpm. Reply with what all of those voltages are and we can help from there.
Cranking voltage is not really relevant here. As long as it stays above 10.5 volts while cranking, it will start.

Chester
 
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Water Crafts
1998 Sea Doo GSX Limited
#11
Cranking voltage is not really relevant here. As long as it stays above 10.5 volts while cranking, it will start.

Chester
I’m starting to think the voltage isn’t the problem at this point as i got a new battery and all of the wiring looks sound... I’m still going to record what the voltage does tomorrow and give an update
 

Chester

Premium Member
Premium Member
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Location
Langley, BC Canada
Water Crafts
98 SXi Pro
#12
You have to check the voltage to test the charging system. Put your voltmeter on the battery and take note of the voltage (12.6 0 12.8). Then start the engine and rev it up. The voltage should go up to over 13 volts, not down. If it goes down, test the resistance of the stator. The manual has the information you need.

Chester
 

JeremyD615

Well-Known Member
Messages
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53
Location
Nashville, TN
Water Crafts
1995 Sea Doo Speedster
1995 Sea Doo XP
1996 Sea Doo XP
#13
Cranking voltage is not really relevant here. As long as it stays above 10.5 volts while cranking, it will start.

Chester
You’re right, it’s not relevant to the plugs fouling, but it is a good indicator of battery health, so I was hoping to get that voltage to help rule out problems with the battery itself. Now that he’s changed it, it’s a moot point though...
 
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Water Crafts
1998 Sea Doo GSX Limited
#14
You’re right, it’s not relevant to the plugs fouling, but it is a good indicator of battery health, so I was hoping to get that voltage to help rule out problems with the battery itself. Now that he’s changed it, it’s a moot point though...
Voltage dropped to about 11.5 when cranking, never dipped below 12.5 when idling or accelerating up to 5000 RPMs. Thankfully i don’t think the MPEM or anything like that is the issue. Still won’t start in water under load... hmm
 

JeremyD615

Well-Known Member
Messages
483
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53
Location
Nashville, TN
Water Crafts
1995 Sea Doo Speedster
1995 Sea Doo XP
1996 Sea Doo XP
#15
Well the cranking voltage is fine. I think your electrical system is okay at this point, so I would move on to checking your compression next. 150psi is what you are looking for, and anything over 135 should be okay as long as both cylinders are close to each other. Less than that and you are looking at a rebuild...
 
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Water Crafts
1998 Sea Doo GSX Limited
#16
Well the cranking voltage is fine. I think your electrical system is okay at this point, so I would move on to checking your compression next. 150psi is what you are looking for, and anything over 135 should be okay as long as both cylinders are close to each other. Less than that and you are looking at a rebuild...
Do you think the compression would go bad after 120 hours?
 

JeremyD615

Well-Known Member
Messages
483
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53
Location
Nashville, TN
Water Crafts
1995 Sea Doo Speedster
1995 Sea Doo XP
1996 Sea Doo XP
#17
It’s possible. The only way to tell is to put a gauge on it and see... Hard to start in the water is one of the symptoms of low compression though...
 

Chester

Premium Member
Premium Member
Messages
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Location
Langley, BC Canada
Water Crafts
98 SXi Pro
#18
Voltage dropped to about 11.5 when cranking, never dipped below 12.5 when idling or accelerating up to 5000 RPMs. Thankfully i don’t think the MPEM or anything like that is the issue. Still won’t start in water under load... hmm
You didn't say what the voltage goes up to when you rev it up to 5000 RPM. No need to do a compression test, it's irrelevant to your problem.

Chester
 
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Location
Virginia Sea Level
Water Crafts
2001 Sportster LE 951 Carbed
#19
Post the highest voltage. 12.5 is low unless it's still trending up. The battery won't be receiving charge current otherwise, meaning your stator power isn't reaching the battery.

If the MPEM regulator is kaput, an external can be wired in it's place.
 

JeremyD615

Well-Known Member
Messages
483
Likes
53
Location
Nashville, TN
Water Crafts
1995 Sea Doo Speedster
1995 Sea Doo XP
1996 Sea Doo XP
#20
Guys I got a little confused on this one too... The way I’m understanding this now, is the OP has replaced the battery and now has proper voltage, but the ski will only start out of the water...

OP, you should still give us what the upper limit of the voltages you were seeing is, and let us know if you are still getting the flattery light on the multi function gauge. Then I still think you should compression test it, as that’s unfortunately one of the more common causes of running on the trailer but not in the water...
 
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Water Crafts
1998 Sea Doo GSX Limited
#21
Guys I got a little confused on this one too... The way I’m understanding this now, is the OP has replaced the battery and now has proper voltage, but the ski will only start out of the water...

OP, you should still give us what the upper limit of the voltages you were seeing is, and let us know if you are still getting the flattery light on the multi function gauge. Then I still think you should compression test it, as that’s unfortunately one of the more common causes of running on the trailer but not in the water...
I am planning on taking it in for a tune up so a more experienced mechanic can check it out... but only this once, after that I’m doing all the repairs/maintenance. Yesterday when i started it on land to record the voltage i didn’t get the “12VLow” message at all. Again, I’ll keep everyone posted
 

JeremyD615

Well-Known Member
Messages
483
Likes
53
Location
Nashville, TN
Water Crafts
1995 Sea Doo Speedster
1995 Sea Doo XP
1996 Sea Doo XP
#22
I am planning on taking it in for a tune up so a more experienced mechanic can check it out... but only this once, after that I’m doing all the repairs/maintenance. Yesterday when i started it on land to record the voltage i didn’t get the “12VLow” message at all. Again, I’ll keep everyone posted
I understand the thinking behind that, but be cautious about taking the ski in. The symptoms you are having are a good opportunity for a dishonest mechanic to take advantage of the situation, so do your due diligence before you greenlight having him do major repairs. If they tell you it needs a rebuild, be sure to ask him what the compression readings were and why he thinks it needs to be done. I would also have the carbs done with genuine Mikuni rebuild kits at the same time if you have to have it rebuilt. Carb/fuel issues are the most common cause of trouble on these skis, so the last thing you want to do is put a new motor in without correcting the issue that caused the current one to fail... Hopefully the motor is healthy and it doesn’t need it, but I want you to be aware of those things if it does go that direction...
 
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Water Crafts
1998 Sea Doo GSX Limited
#23
I understand the thinking behind that, but be cautious about taking the ski in. The symptoms you are having are a good opportunity for a dishonest mechanic to take advantage of the situation, so do your due diligence before you greenlight having him do major repairs. If they tell you it needs a rebuild, be sure to ask him what the compression readings were and why he thinks it needs to be done. I would also have the carbs done with genuine Mikuni rebuild kits at the same time if you have to have it rebuilt. Carb/fuel issues are the most common cause of trouble on these skis, so the last thing you want to do is put a new motor in without correcting the issue that caused the current one to fail... Hopefully the motor is healthy and it doesn’t need it, but I want you to be aware of those things if it does go that direction...
Thanks man, I definitely was thinking along those lines but it doesn’t hurt to hear it again and from somebody with some more experience. I should’ve taken some pictures so you all could see that the machine is really in great condition, which is why i’m so frustrated it’s giving me a little trouble lol. But yeah I’m definitely on a budget so unlimited repair costs aren’t even an option
 
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Water Crafts
1998 Sea Doo GSX Limited
#24
Thanks man, I definitely was thinking along those lines but it doesn’t hurt to hear it again and from somebody with some more experience. I should’ve taken some pictures so you all could see that the machine is really in great condition, which is why i’m so frustrated it’s giving me a little trouble lol. But yeah I’m definitely on a budget so unlimited repair costs aren’t even an option
Also the carb was rebuilt by the previous owner, so that won’t be needing any work
 

JeremyD615

Well-Known Member
Messages
483
Likes
53
Location
Nashville, TN
Water Crafts
1995 Sea Doo Speedster
1995 Sea Doo XP
1996 Sea Doo XP
#25
Well my recommendation would be to try to diagnose the problem before taking it in, as most issues with these skis can be dealt with inexpensively at home and then if you have to take it in, you know exactly what work they need to do...

The carbs being rebuilt by the previous owner wouldn’t change anything for me. The internal passages on these carbs are really small and easy to clog up, and the ethanol gasoline that we have these days does not help. For the $100 or so that it costs for all of the correct rebuild parts, I would never replace a motor without going through the fuel system at the same time...
 

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