Sea-Doo RPM drop question

A few weeks ago I was riding my 97 SPX and noticed a drop of approximately 500 RPM or so. I assumed it was carburetion problems since I was dinking around with the low/high and idle settings to try to dial it in. Anyway once I started losing the RPM I packed it up for another day.

Yesterday I went out to test one final time, tiny tach in hand before I would make the decision to take it to Watercraft Magic (where I know it would be fixed) or attempt to troubleshoot it myself. I rode it around and was turning about 6800 RPM. A bit low from the 7000 (Factory spec 1) figure I once had about six months ago.

Despite a few hundred RPM drop the ski did run good for about 30 minutes. Then the RPM went down to about 6200. When I hit the shore to look inside the engine compartment, the pipe chamber body was white (salt deposits on a hot pipe). The chamber body was hot enough to sizzle water. Now I knew something was really wrong. The chamber body normally gets hot enough to want to take your hand away after holding it on there for five seconds but it never sizzled water.

I pulled it out of the water and verified that all the cooling lines were clear, they were. The cylinder, cylinder head and head pipe were normal temperature. Only the pipe chamber body was hot. This made me look at the waterbox regulator since it seems to be the only source of water for the chamber body.

When I opened it, a bunch of water pored from it. The diaphragm came unseated. I reseated it and blew into the regulator verifying the normal up and down movement and it seemed to be seated well. Reinstalled it and hit the water. 6900 RPM, still a bit low but the speed was back……..for about 15 minutes…..then back down to 6500 RPM. I popped open the regulator and the diaphragm was unseated again.

When I reinstalled the diaphragm it seemed to be in nice and tight. It takes quite a bit of force by hand to pop it out.

1) Is it just worn out?

2) How much pressure should it be able to handle before it unseats?

3) Could something else within the system be causing excess pressure build up in the waterbax causing it to unseat?

I am just asking these questions before I drop $100.00 on a new regulator.

You might want to try and richen up your carbs a tad. Cooler temps require slightly more fuel. A slight lean condition will reveal itself with lower RPMs at first. Sounds like you are close, but a little more fuel may take care of it. Bear in mind that the hotter than normal water temps in your motor (due to a lean condition) will cause things to expand and loosen up, which may be causing your diaphragm to work loose.

Lazslo, He is talking about the diaphram on top of the waterbox. It should never get hot with the cool water from the pump going in and out of it.

He may need to use a thin tie-wrap around the base of his diaphram to secure it to the regulator body to keep it from coming off.

Some guys just eliminate the regulator alltogether and use hard jetting in the pipe and in the waterbox. 120 pipe, 140 waterbox, and a plastic tee.

Bill O'Neal WCM Carolina Watercraft Works, Inc. wrote in message

I agree, but don't couldn't it be possible that the steam created in the pipe jacket could work it's way back down to the waterbox valve causing the expansion? There should a clamp at the small end of the diaphram and a clamp at the big end. And he stated the pipe itself was hot, not the water box. Something is causing the pipe to get hot. It's either a blockage, or it's too lean.

BTW ciocca, the majority of the water for the pipe is supplied via the engine, through the exhaust manifold and into the top of the head pipe.

You might want to try and richen up your carbs a tad. Cooler

I have the plugs with a nice brown color doing my high spped kill the throttle runs. The RPM only drop when that damb regulator diaphragm pops loose. Aslo only the 'Chamber Body' got hot. The head, cyclinder case, and head pipe were normal temp. The only water the chamber body sees is from the regulator??? correct??? By the way Bill recommended a tie wrap??? Isn't the plastic of the regulator too hard to compress with a tie wrap?

Ok, I thought you meant the pipe itself was getting hot.

In that case, I would look closer at your diaphragm like you were. There is supposed to be a clamp on both ends of the diaphragm to help keep it on. If they are gone, a tie wrap, like Bill mentioned, should suffice.

you might want to go ahead and just hard jet system like bill said ,allso install inline filters chip d. pcb

Laszlo, The round plastic piece (at the bottom of the inside) that snaps into the regulator (the one with the two small holes) is what is unseating. It is attached to the actual diaphragm that I bilieve you are talking about (that has the clamp). If that part is worn out, I will just replace the assembly vs messing around testing with a bunch of sub components. I just want to know if the waterbox due to some defect is capable of super high pressures that could cause it to unseat.

As far as hard jetting is concerned, won't that pull down peak RPM since water will always be injected into the chamber body vs being cutoff by the regulator?

The problem is not the diaphram, it is the piece below the diaphram. It keeps poping out of it's seat, shutting off all water to the chamber of the pipe. Either hard jet it or replace the water regulator.

Lazslo, the water is injected into the inner pipe from the regulator, steam from the water jackets has no way to travel back through the tube to the regulator.

He is asking if it is possible for backpressures from the waterbox to cause his regulator to unseat itself. I think he needs to squeeze the hose from the WB to the outlet to see if it has delaminated, blocking his exhaust. I have seen hoses that look fine, but when you actually feel them, they feel soft and delaminated to the piont that they will block the exhaust system. Shaking the muffler for rattling metal is a sure sign of a broken baffel, which can be a sourse of blockage too.

Bill O'Neal WCM Carolina Watercraft Works, Inc. wrote in message

You are right about the hoses. The Kawi 650 used to be very susceptible to that. I even diagnosed that very same thing to Andrew (Able2ski) a while back and just replaced one on an XPL in right now. Didn't think about it at first, but now that you mention it, that sounds very much like what he may be experiencing.

But water is also supplied to the pipe via the exhaust manifold.

take off that piece of crap water regulator and just hard jet everything. I hate that regulator. My ski never ran better till I took off that POS and just hard jetted the pipe.