1996 Seadoo GSX Fix

[IcyBlueMink]

Hi all, recently I picked up another ski which happens to be a 1996 GSX everything is decent on the ski and it’s low hours but the PO said it would only go to about 4K RPM. Well he was correct so I went through and did a mild tune up and still no change. Ski runs great with the red wire on the rectifier disconnected but I put a new rectifier in and the problem persists. Are these commonly shipped out faulty or am I possibly looking at another issue? Thanks!
-Logan

 

[GGuillot]

I went through and did a mild tune up

What was the mild tune up? You say the ski runs great with the red wire on the rectifier disconnected? What do you mean? Yes, it's possible to get a defective new rectifier. But most of the problems like you describe are fuel system related. Personally if it were me picking up a 24 yr old ski, low hours or not,, as a precautionary I'd do the full carb rebuilds, new fuel lines, new fuel selector and check the compression to see where the engine is.

 

[IcyBlueMink]

PO replaced fuel lines with the proper ones, I cleaned the carbs everything on the inside looked to be in good shape and almost as if they’d been recently done, set H and L needles to stock settings, new plugs, chopped 1/4 inch off the wires, fresh fuel and oil. Compression is 147/146. Everything about the motor seems healthy minus the fact it’s smacking the rev limiter at 4K rpm. I did 2 sets of plug chops on the lake yesterday and both looked healthy with a good burn to them. Spark is great as well. I’m nearly sure the rectifier is the issue I just don’t understand why when I replaced it with a brand new one out of the package the issue persists. The ski will hit the limiter at 4K with the red wire plugged in. As soon as you unplug it it runs great and plug chops looked good.

 

[GGuillot]

Aftermarket rectifiers are a hit or miss, sounds like you got a bad one..

 

[IcyBlueMink]

Where’s the go to place to buy a good one? I don’t mind the cost just don’t have time to fool with a junk one.

 

[GGuillot]

Where’s the go to place to buy a good one? I don’t mind the cost just don’t have time to fool with a junk one.

Try OSD Marine.

 

[IcyBlueMink]

Have replaced the rectifier with 3 separate ones now and still have the same issue. Runs with red wire disconnected and doesn’t run well with it connected. Anyone have any saving graces before I can’t ride this 4th?
Thanks

 

[GGuillot]

Have replaced the rectifier with 3 separate ones now and still have the same issue. Runs with red wire disconnected and doesn’t run well with it connected. Anyone have any saving graces before I can’t ride this 4th?
Thanks

What voltage are you getting at the battery? At idle and when you rev?

 

[TCircuitry]

Me and my brother are having the same stupid problem, I have rebuilt the carbs, installed new fuel lines, rebuilt the engine properly, fixed an issue with the gas tank not venting properly, and the stupid boat wont rev above 4k rpm. Its just beyond frustrating.

 

[IcyBlueMink]

Hey T, if you manage to figure it out let me know. I’ve done all that as well minus the rebuild. These damn electrical gremlins kill me. I figured a rectifier would save my day and I just can’t understand what’s going on. Will be checking with the multimeter tomorrow at the battery.

 

[TCircuitry]

I currently just checked the popoffs on the carbs to see if anything was out of wack, they both read a consistent popoff pressure of 30 PSI. I had unplugged the red wire from the rev limiter and nothing changed. Still limited to 4,000ish RPM. We cleaned the RAVE Valves, still nothing. I am now checking to see if I got the rotary valve timing off by a few degrees since I have the carbs off anyways. What really sucks is I dont see a conclusive answer on any of these forums, except another forum site where they just cleaned the carbs, but I dont readily see anything wrong with my carbs, and my spark plugs confirmed this, they werent rich, nor were they lean.

 

[IcyBlueMink]

Sounds about right. I went through these carbs and they looked about spotless. When I unplug the red wire mine runs fine and everyone else says it’s a rectifier. Well I’ve tried 3 different ones and that’s not the case. Unfortunately I haven’t been able to find a forum solving an issue like mine either.

 

[TCircuitry]

Well if there was anything i messed up on during assembly i shall let you know! That sucks to hear man, these should really be simple to work on and fix but they arent.

 

[IcyBlueMink]

What voltage are you getting at the battery? At idle and when you rev?

Checked the voltage. 12.5 resting, 12.6 idle and about 12.8 when revved.

 

[GGuillot]

Checked the voltage. 12.5 resting, 12.6 idle and about 12.8 when revved.

Too low, you should easily see it in the mid 13 volt range at idle and revving. The ski can run like shit under heavier demands if the electrical system can't keep up.

 

[TCircuitry]

Found out that my brothers rotary valve timing was off by 15-20 degrees, i installed it incorrectly when we rebuilt the engine. Going to take the boat to the water now to see if that fixes it. I recommend checking the timing on the engine if someone else before you messed with the boat.

 

[IcyBlueMink]

Too low, you should easily see it in the mid 13 volt range at idle and revving. The ski can run like shit under heavier demands if the electrical system can't keep up.

I’m going to double check those numbers here in just a bit when the sun goes down some. My sister who is not so mechanically inclined read the multimeter so I think the 12.8 was closer to the idle. And I saw bumps into the mid 13 range while on the gas. Grrrr.

 

[TCircuitry]

On another forum I saw that someone had failing O-rings in the head of the engine, causing water to leak out slowly into the cylinder when the engine was revved up, and water in the gas prevents the spark plugs from burning the fuel efficiently. Youd have to unplug your cooling in the water and see if your power bumps up, If it does, you have a head gasket leak somewhere.

 

[IcyBlueMink]

On another forum I saw that someone had failing O-rings in the head of the engine, causing water to leak out slowly into the cylinder when the engine was revved up, and water in the gas prevents the spark plugs from burning the fuel efficiently. Youd have to unplug your cooling in the water and see if your power bumps up, If it does, you have a head gasket leak somewhere.

My issue has got to be electrical. I just can not figure out where I need to go now.

 

[GGuillot]

My issue has got to be electrical. I just can not figure out where I need to go now.

I'd turn attention to the coil and timing, though timing off it should be backfiring, but not always. Have you trimmed the coil wires 1/4" on each end? This would improve connectivity getting from the coil to the plugs. Sometimes it works.

I'd double check the timing if you haven't already, the PO might have done something prior to cause it, plus you need to get a good look at the rotary valve surfaces, if scored bad it can scavenge between cylinders. But again it would usually backfire. You'll need the carbs and Rotary Valve cover off and a degree wheel to verify. TDC on the MAG cylinder, I eye and feel for it watching a 1/4" extension going up and down while turning the PTO.

I have two 787 skis and this would be next move...they're pretty simple operationally, there's not much else to check.

 

[IcyBlueMink]

Turn attention to the coil and timing, though timing off it should be backfiring, but not always. Have you trimmed the coil wires 1/4" on each end? This would improve connectivity getting from the coil to the plugs. Sometimes it works.

I'd double check the timing if you haven't already, the PO might have done something prior to cause it, plus you need to get a good look at the rotary valve surfaces, if scored bad it can scavenge between cylinders. But again it would usually backfire. You'll need the carbs and Rotary Valve cover off and a degree wheel to verify. TDC on the MAG cylinder, I eye and feel for it watching a 1/4" extension going up and down while turning the PTO.

I have two 787 skis and this would be next move...they're pretty simple there's not much else to check.

The timing cover has never been off. I can still see where the paint had pooled at the joint between the cover and the case. What cool should I be checking? The ignition or the pickup in the mag housing? I already trimmed the wires and slapped a little grease in there.

 

[GGuillot]

The timing cover has never been off. I can still see where the paint had pooled at the joint between the cover and the case. What cool should I be checking? The ignition or the pickup in the mag housing? I already trimmed the wires and slapped a little grease in there.

How does it look in the ebox where the coil is? clean? no rust at the grounds, etc? The mag pickup could be a problem, pain to get to with the engine still in. I think the mag pickup is more binary, it either works or it doesn't, and the ski running..

The reason I said I'd pull the RV cover is little screws are known to go down the intake and score up the surfaces causing issues. Doing everything you've done so far I'd at least look at it, verify, and rule it out.

 

[IcyBlueMink]

How does it look in the ebox where the coil is? clean? no rust at the grounds, etc? The mag pickup could be a problem, pain to get to with the engine still in. I think the mag pickup is more binary, it either works or it doesn't, and the ski running..

The reason I said I'd pull the RV cover is little screws are known to go down the intake and score up the surfaces causing issues. Doing everything you've done so far I'd at least look at it, verify, and rule it out.

I think I might test the ignition coil tomorrow and see if maybe it’s not fully functional. Everything in the ski is very clean but im going to double check it all again tomorrow. The tigger coil I assume to be working fine since the ski still runs but I know when they get wore out the sometimes can’t keep up with the RPMs.

 

[TCircuitry]

When you do your ignition test, unplug one of your plug wires and see If it will idle or attempt to run on one cylinder. If one of those cylinders wont run, change your plugs, or unplug your plug wire and trim it back 1/2 an inch, seems to fixed my problem, we are taking them down to the water today, will reply back.