Surging 1997 Speedster....left 717 only.

[Nathan Mayo]

Here's the stage for it all. Lengthy, but I want you to understand. Newly done Premium SBT reman engine (717) on right side. Runs great through all throttle ranges by itself. Older 717 on left side somewhat weaker, but also runs great through all ranges by itself. Carbs have both been ultrasonically cleaned until they squeak. Compression good on all 4 clylinders. Doesn't matter what plugs I have in. The MPEM was fried a year ago and has been replaced with a workaround rig job of 2 MPEM's from jetskis.

Problem.........either engine BY ITSELF runs great, but when both are going, no matter what throttle setting on the right side, the left one will surge....on/off....on/off. Cut the right one off.... and wham!......left side runs great.....until you turn the right one back on....then its on/off....on/off for the left one again. Don't know if this is significant, but if both are WOT and left is doing the surge......when I back the right one back to half throttle, the left one will probably die. Both crank instantly and idle fine together, but when I rev them up together that's when the surging starts.

My factory trained mechanic is baffled. 1. If gas was bad or water contaminated, neither would work.
2. If fuel pickup tube was partially blocked, or if the left fuel selector valve was crudded up, then the left side should not run right at any time.
3. My thought about the MPEM replacement is that if something electrical was the prob then the left should not work at all, but I am a clueless dentist and we did not cover that at Tooth U.

We are at a complete loss on this one for what to try next. Any thoughts would be welcome, but please don't bother to tell me to rebuild the carbs unless you know something.

Mechanic suggests I try switching the fuel lines to see if the problem switches sides, but even if it does we still don't know why this is happening.....or do we?

I am dying to hear what you guys have to say about this. Thank you..........Nathan Mayo


Here's how the story ended. After the factory guy gave up, I went back to the guy who originally changed out the burned up MPEM with the Internet rig job 2 MPEMs. Took him awhile, but he finally determined that one of the MPEMs was no good, changed it out, and the boat now now runs like a cat with kerosene on its ass. I am a happy dog.............for now, but knowing Seadoo there will another disaster soon enough................Nathan Mayo

 

[howie099]

Did you pull the fuel baffle to see if it ok? Since both engines pull from it there might be some hole in the one of the lines or a clogged pickup filter. Could be sucking air from the external fuel filters also, those gaskets leak all the time.

 

[Sportster-2001-951C-Stock]

I guess there are two voltage regulators. I'd try disconnecting the red wire of one and then the other to isolate a potential defective voltage regulator.

If the regulator is passing AC to the DC output, or exceeding normal voltage (less than 14.2v, mine regulates at 13.8v), this can cause the CDI ignition to malfunction. Since it's the right engine at WOT that seems to be causing the left to malfunction, I'd start with that one.

Just an idea of something to try...

 

[Nathan Mayo]

Thank you for the idea. Since it such a stinkin' job to pull that thing out, I am going with the other fellow's thought for now because it is much easier to get to the electrical panel. Will pass this to my mechanic for his comment

 

[Nathan Mayo]

This idea I like because 1. It should relatively easy to try 2. cheap to fix 3. It would explain why the surging if the right engine is ON and steady, no matter what the throttle setting. With howie099's idea above I would suppose that the surging would vary according to how open or closed the right throttle was. It does not. I think the electrical angle would explain a lot. I will ask Greg, the head dog of the Service Dept. to chase in this direction and get back here when we have some results one way or the other. Thanks to you both! Nathan Mayo

 

[howie099]

You have now 2 separate mpems do they should run all the electrical separatly for each engine. The electrical shouldn't matter on what the other engine is doing unless something is wired wrong or you have a bad mpem.

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[Sportster-2001-951C-Stock]

One additional thought is, the 717 in boats usually has a divorced fuel pump not the carb-mounted fuel pump. Those original pumps are known for getting tired.

You could swap the two fuel feeds to isolate.

 

[Sportster-2001-951C-Stock]

You have now 2 separate mpems do they should run all the electrical separatly for each engine. The electrical shouldn't matter on what the other engine is doing unless something is wired wrong or you have a bad mpem.

Sent from my SAMSUNG-SGH-I317 using Tapatalk

If the two engines were completely isolated electrically, that would require 2x cranking batteries and probably the harness would need some additional wires added (isolated power for the 2 MPEM's), I'm thinking the two regulators are both charging into the same system same as factory setup.

Assuming this is a single battery configuration....

If you're operating both engines, only one regulator is needed for charging the battery so the other regulator can be removed completely. Having both regulators hooked up and functional will provide extra current for charging faster.

The OP could simply disconnect the one that defective and leave it that way as long as the other was still functioning correctly. Or he could have them both functional if he preferred.

 

[racerxxx]

If one regulator is indeed bad, I would not just run one. It's a $9 part used from OSD and another $8 to ship it, and it would be right in front of you, so why leave it unhooked?

 

[howie099]

2 charging systems are better than one. For $20 that should be no brainer fix there. If each each engine runs fine by themselves and they start to act up when both are running what do the engines share? Is the surging feel like fuel or electrical?

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[Nathan Mayo]

Since you are the moderator, you are obviously smarter than me. Here is the latest development. Local Seadoo factory guy finally gave up on the surging problem and we dropped it back into the lap of the local guy who installed the double MPEM rig job. After a month he has decided that an ignition coil is bad and needs replacement. He tells me he swapped one off of a working jetski and that did the trick, but he has not lake tested it yet or installed the new part. Here's my thought.....BOTH engines have coils...right? If a coil was indeed bad, would that engine run at all ? If you you reread the description above you will see that both engines will run fine by themselves. It is when they are both running at the same time that the surging occurs. I know nothing of things electrical. I would think that dead...is dead..is totally dead. Is it possible for a coil to be good enough to run an engine, but sort of sick so that it steals mojo from its neighbor, causing it to run intermittently with pulses every 1/2 second? I want to believe that this guy is right, but HE is the one who installed it a year and a half ago and has forgotten he did it. Also if it IS the coil thing, should he have detected this problem back when he put in the MPEM's? Are they part of this coil thing? The boat has not truly run right since the MPEM fix, and I don't want him to charge me $800 to diagnose and repair something he missed in the first place. Thanks for whatever light you can shed on this. Nathan Mayo

 

[jhjesse]

Two systems - two batteries = good
Two systems - one battery = questionable

 

[racerxxx]

Are these aftermarket mpems?

 

[Fat Tony]

If one regulator is indeed bad, I would not just run one. It's a $9 part used from OSD and another $8 to ship it, and it would be right in front of you, so why leave it unhooked?

Can you post a link to the rectifier? The only one I can find on OSD for this year boat is $40

 

[Nathan Mayo]

OK, go slow with me here, because I do not know what I am talking about. I have been under the impression that juice from the battery STARTS the engines and then juice PRODUCED BY the engines keeps them running. From what I read yesterday I now get the idea that the battery STARTS them and CONTINUOUSLY feeds them while running. The engines job is to supply the battery.....the battery's job is to supply enough juice so the coils can jump it to a bazillion volts and keep the plugs happy. Is that correct? If so, then I can understand why a coil that is somewhat marginal could keep things going if it was the only one sucking off the battery, but two might overdo it.......the good coil would weaken the current flow to the point that the bad coil could not do its job. Does it sound like I am starting to get it?

I still question whether or not this problem should have been caught during the original MPEM repair. Can a coil just croak at any time? Would those coils have been included along with the replacement MPEM set? The mechanic bought them and put them in, so I have no idea who made them. I was just told that some guy on the WEB had cobbled jetski MPEM's together so they would run a boat like the Speedster, so here I am. Please tell me that I am now understanding how an ignition system works, and if I'm not, then please enlighten me.

Here's a snappy quote I just made up that seems to fit here.........."Sometimes ignorance is bliss, and sometimes its a real expensive pain in the ass". Help, please............Thanks!.....Nathan Mayo

 

[howie099]

I still don't see how one coil could mess up both engines. The coil should only affect 1 engine. Unless they botched the the MPEM splice and some wires were touching or not good grounds somewhere. I really don't see why you couldn't share one battery. My single MPEM powers 2 engines and I have one battery but everything else is doubled just like your setup. I am sure the single MPEM is just like 2 MPEMS merged in 1 big unit. Each engine runs independent of each other since I heard of people burning out just one side of the MPEM so only one engine works.

 

[wfo speedracer]

OK, go slow with me here, because I do not know what I am talking about. I have been under the impression that juice from the battery STARTS the engines and then juice PRODUCED BY the engines keeps them running. From what I read yesterday I now get the idea that the battery STARTS them and CONTINUOUSLY feeds them while running. The engines job is to supply the battery.....the battery's job is to supply enough juice so the coils can jump it to a bazillion volts and keep the plugs happy. Is that correct? If so, then I can understand why a coil that is somewhat marginal could keep things going if it was the only one sucking off the battery, but two might overdo it.......the good coil would weaken the current flow to the point that the bad coil could not do its job. Does it sound like I am starting to get it?

I still question whether or not this problem should have been caught during the original MPEM repair. Can a coil just croak at any time? Would those coils have been included along with the replacement MPEM set? The mechanic bought them and put them in, so I have no idea who made them. I was just told that some guy on the WEB had cobbled jetski MPEM's together so they would run a boat like the Speedster, so here I am. Please tell me that I am now understanding how an ignition system works, and if I'm not, then please enlighten me.

Here's a snappy quote I just made up that seems to fit here.........."Sometimes ignorance is bliss, and sometimes its a real expensive pain in the ass". Help, please............Thanks!.....Nathan Mayo

Actually no, the battery starts the engines, the stator recharges the battery through the regulator-rectifier. The regulators on 717's should have nothing to do with the running of the engine. These ignitions system are AC, they get their current from the stator , the stator has separate coils that the ignition runs off of. Now I have seen stators go out and cause really strange running issues on 717's, you could also have something weird going on with one of the MPEMS.

I would try to swap the MPEMS's and see if the problem moves to the other engine ,same with the CDI-ignition coils swap them and see what transpires.

At any rate you are going to have to find some way to narrow the problem down that doesn't involve replacing expensive parts that may still be good.

 

[Nathan Mayo]

Reading back through all of this I realize this garbage has been plaguing me for 3 solid YEARS! No wonder I feel old.......OK, enough whining (for now). Regulator -rectifiers are new....replaced a couple of months ago by Seadoo Factory techs with no result. The guy currently struggling with it has ordered a new coil and will be putting it in soon and thinks all my troubles will soon be over.....he says. I will post and tell everybody the latest outcome when it happens. In the meantime, thanks for all of the input. Since my leafblower just died because the ignition coil croaked, I know that it can happen out of the blue.

Did I mention lately that I think Seadoos are designed by the Devil? Happy New Year to all...................Nathan Mayo

PS: Do you like my new avatar....or should I go back to the red Z Car? I personally find it amusing...........

 

[Meach]

Awesome avitar. It depicts my feelings on that subject to the T

 

[Sportster-2001-951C-Stock]

I dunno, sounds more like some kind of crosstalk between the two MPEMs to me.

Another idea I don't consider likely but maybe?: Have you looked into the throttle interlock? Earlier boats have the throttle interlock (might just be 787 boats) but the skis don't. So if the MPEM's are from a ski then likely not the issue.

The way the throttle interlock works is it won't allow the engines to rev past 3500RPM or something like that unless the switch for forward/reverse is made inside the throttle controller.

The guy who wired this system doesn't recall doing it? lol, that's not encouraging but did it ever work correctly?

 

[Nathan Mayo]

Thanks. I found it at a car show here in Central Florida and it made me smile. It is currently gracing the front desk area of my dental office. For your sake, I hope your Speedster treats you better than mine does me.............nm

 

[Nathan Mayo]

I tend to agree with your first sentence because each engine runs fine as long as the other is not turned on.

The latest development is that he put in a new coil this week, sez everything worked fine for 15 minutes and then the evil left engine started running ragged, so now he's saying to maybe replace the MPEM on that side. It is brand new, so I don't like that much. I will ask him to switch side to see if that transfers the problem to the other engine.

No, I do not think it has ever run right since the initial install, but there have been so many other probs with the stinkin' boat I cannot be sure that the electrical side of it was going on then

 

[ialonso]

FUEL PUMP! FUEL PUMP!

Can you jerry rig an electric fuel pump in front? or try high flow pumps? The jetting for internal pump is different that external. I bet $5 you have a fuel problem.

If you can put a fuel bulb before the carb end temporarily and try pumping..there should be zero bubbles once you get a flow going. Sinc eyou have been hunting this for a while I would consider a small external tank to troubleshoot, or an electric rigged fuel pump in front to troubleshoot.

Best of luck!

 

[Andy4k6]

I suggest you need a new mechanic it appears he is throwing parts at your boat at your expense trying to fix it.

He should have checked that faulty coil with an oscilloscope and if he couldn't do that should have at least swapped it from the other engine.

I'm thinking this is a fuel issue, it could also be something as daft as the fuel tank vent not allowing enough air into the tank creating a vaccum and the fuel pumps are fighting for fuel.

I would start by swapping the fuel lines, if that doesn't work I would also try swapping the carbs and see if the fault follows.

Andy