947 experts I need your input.

[AKnarrowback]

NUTS......

My 98 XP that I just got going died today. I think I seized it 4 times. It felt like it might have been a fuel starvation shutting the motor off, but the compression and visual check says otherwise.

The damage is identical on both cylinders. It is concentrated on the opposite side of the carbs, both cylinders have identical wear patterns. The cylinders were recently bored over and used oem pistons matched to the bore job. The carbs were rebuilt with all mikuni parts from osd marine. Machine was broken in properly and has run perfect up to this point.

The only thing I can think of is on the last ride I spun out, submerged the nose deep and a few seconds later had the motor act like it got a little water through the intake. It bogged out, started right up and ran 500 rpms low for about 30 seconds before it cleared out. That was at the end of the last ride, I rode it around for 5 minutes to dry things out. The seizure today happened within 5 minutes of the start of the ride running at wide open throttle. The other 3 shut downs were also at wide open throttle, lower throttle settings did not cause a shut down. compression was 113/120. I did check the filter bowl. It had 1/4 water in it, the inside of the filter also had standing water in it at 1/4 full. Water on both sides of the filter element.

It seems like one incident of light water ingestion through the intakes should not have caused a failure.

I have not taken the carbs apart to see if there is contamination in the filters. But the cylinder damage doesn't look consistent with a lean condition.

The rest of the cylinders surface still looks like it came straight off the hone. Only that tight area opposite the carbs and exhaust has wear.

The wear does look like water damage.

The cylinders are already bored. I do have a set of standard oem pistons for this motor. A quick look shows sleeves to bring them back to standard bore anywhere from $55 to $65. Any suggestions on who makes a good sleeve?

I'm not familiar with this motor and need some more experienced Input on this one.

Thanks.

AK

 

[AKnarrowback]

Jojo said "Dude, you're screwed". Then told me the muffler bearing broke. Not going with her assesment.

 

[AKnarrowback]

Jojo said to just get the motor back in this one since the season is almost over.

 

[AKnarrowback]

Jojo figured this one out before I did....... The look of disgusted amazement says it all.

They told me my mind would start getting fuzzy at 50. How the F$%# did I not see this when I was torquing the head down.....

Some days I amaze myself, on others I couldn't find the hat on my head.....

 

[mikidymac]

If it is just on the exhaust port side then probably a lean seizure.

Group K "The classic lean seizure exhibits heavy scoring and seizure along the entire width of the exhaust port with only light scoring on the opposite piston faces. In lean mixture conditions, the exhaust gas temperatures escalate quickly into the meltdown stage. Those high temperature gases can compromise or completely burn off the oil film on the exhaust piston face as the exhaust port is being covered up. With the oil film weakened or gone, scoring quickly turns into seizure and ring locking."

Given that water was in the water separator there is a chance it got into the carbs. Once water gets into the carbs it stays there and acts like a moving restriction that can plug up a jet and run really lean then fall back down into the carb and run fine until it gets sucked back up into the jet again. I would also check the exhaust pipe joint because that can leak water and wash the oil film off the pistons too.

More words of wisdom from Group K...
"Some fundamentals - Many people believe that piston seizures occur when engine heat causes the piston to expand larger than the size of the cylinder bore...this is not true. If you could freeze your engine "in motion" in the middle of a long full throttle pass, and disassemble it for micrometer measurement, you would find the piston to measure at a .0005" to .0015" press fit into the bore. That's right, a slight press fit! The reason that it doesn't seize is because the premix oil has such a terrific film strength that it acts as an irremovable buffer between the piston and the cylinder. That is, the bare metal surface of the piston never actually touches the bare metal surface of the cylinder because the oil stays between them. Many mechanics have experienced this phenomenon while cleaning a freshly bored cylinder. Completely dry without cleaning solvent, the piston moves through the bore with difficulty. After rinsing the piston glides all the way through with no resistance at all. This is because the solvent acts as a film between the piston and cylinder.

A piston seizure can only occur when something burns or scrapes away the oil film that exists between the piston and the cylinder wall. Understanding this, it's not hard to see why oils with exceptionally high film strengths are very desirable. Good quality oils can provide a film that stands up to the most intense heat and the pressure loads of a modern high output engine.

The difference between seizure and scoring Seizure and scoring are two different stages of the same problem. When the oil film on a cylinder is momentarily burned or brushed away, the metal surfaces of the piston and the cylinder wall will actually touch. When this happens, there is a sort of scraping that takes place between them. When the oil film is resumed, the marks from this scraping will often remain on the piston and (or) the cylinder wall. This momentary scraping or "scoring" seldom causes any permanent or performance robbing damage. No significant damage takes place because the oil film is resumed before the piston and cylinder have a chance to start exchanging material onto one another.

Scoring is commonly seen on the piston face directly below the piston ring end gaps. The blast of combustion can get between the large end gap of a worn out ring and burn the oil off the piston and cylinder in that area...Hence the surface scoring. In most cases, score marks can simply be sanded off of the piston and cylinder. However when ever you see scoring, it's a good idea to find the source so that it doesn't develop into a full blown seizure.

Seizure is a case of scoring where the oil film does not immediately return. After a few moments of constant scoring, the piston and cylinder will scratch each other hard enough to remove material from each other. This floating material grinds itself into the piston and the cylinder as it continues to grow in size. As this snowballing material grows, it will drive the opposite side of the piston against the cylinder wall with a pressure so terrific that scoring begins to take place. While all this is going on, your engine is still running wonderfully at full throttle.

The death blow comes when the mass of material between the piston and the cylinder wall finds it's way to the piston ring. This nearly molten mixture of aluminum and iron will instantly lock the ring in it's groove. This ring locking, not the piston surface seizure, is what actually causes your engine to quit. When the piston ring becomes locked back in it's groove, it's incapable of providing compression sealing against the cylinder wall. This instant loss of compression, while the engine is at speed, causes a dramatic loss of power. That power loss, along with the added drag of the badly seized piston, makes the engine quit or lock up in a nanosecond. In fact this entire seizure process, from the first scoring scratch to the piston locked solid, takes less than a second at full rpm. That's not even enough time for you to utter the first syllable of your favorite profanity."

 

[FL-Rider]

If there was water in the filter bowl then how did it get in there? It couldn't get there through the carbs... If you pressure check the fuel system, you should find if there is a leak. On my 98, my gas cap clutch slipped before it would seal the o-ring. I never realized it wasn't sealing until I pressure tested. My pressure relief check valve for the fuel system also failed open. It would piss gas on the ground after filling the tank. I suppose porpoising through a wave hard enough could have forced water into the system. It never happened that I know of because I was doing mostly flat water riding, but I guess it could have under the right conditions. Your tank may also have water in it from condensation.

 

[AKnarrowback]

Thanks guys. I just reread what I wrote and I made it sound like there was exhaust side damage.

All of the damage is on the opposite side of the piston from the exhaust port. Since the area damaged was on the "lower" surface of the piston as it lays in the cylinder I was guessing it was water related. The cylinder still has perfect cross hatch on the exhaust side, no damage at all.

Both cylinders have the exact same wear pattern, both also have the asymmetrical wear from center to the right/pto/rear. Theory is it got water in, it wasn't atomized, the heavier "glob" followed the lowest port into the combustion chamber washing the oil away. The more wash towards the pto side??? Maybe because the water was concentrated to the rear from the nose rising, or under acceleration?????

So those of you familiar with the motor and hull combination can offer some insight. Are these really sensitive to water over the nose entering the hull and dropping onto the carbs? I normally never nose dive my machines, but it appears that one good nose dive took out my fresh motor..... I do have the rubber flaps over the intake, the exhaust manifold to pipe gasket is tight and has the rubber boot over it.

Live and learn. Going through the carbs to check for water obstruction and seeing what got into the tank. Not going to dive the nose under again.

 

[mikidymac]

It was an issue.
On the later ones Seadoo completely closed the front air intakes in the hull.

 

[AKnarrowback]

It was an issue.
On the later ones Seadoo completely closed the front air intakes in the hull.

Thanks Mac.

The one question I should have asked.

On a 947 is it typical to see water damage concentrated on the "lower" surface. To which I would answer "yes", it's where the transfer ports are so where else is there going to be water damage. Answered my own question.

Ok, bore and hone, new pistons, gaskets and some intake redesign on the way.

 

[etemplet]

It was an issue.
On the later ones Seadoo completely closed the front air intakes in the hull.

Just a side note on this issue. I was talking to a shop owner and what he said disgusted me. Not sure if it was only the 951s that were known as unreliable or got a bad reputation. Apparently Seadoo did an upgrade and paid the shops to perform it. He told me it was a water injestion issue and they replaced the airbox and.... were SUPPOSE to rejet the carbs. They DID NOT REJET the carbs because, he said, Seadoo didn't pay enough for that so all they replaced was the air box. Now to me... THIS issue of not rejeting is a likely cause of at least some of the reliability issues and bad reputation reagarding the 951. These guys are maggots !! People bring their skis to make them reliable and this is the kind of stuff that gets done... by Seadoo Shops. Sad.

 

[AKnarrowback]

Just a side note on this issue. I was talking to a shop owner and what he said disgusted me. Not sure if it was only the 951s that were known as unreliable or got a bad reputation. Apparently Seadoo did an upgrade and paid the shops to perform it. He told me it was a water injestion issue and they replaced the airbox and.... were SUPPOSE to rejet the carbs. They DID NOT REJET the carbs because, he said, Seadoo didn't pay enough for that so all they replaced was the air box. Now to me... THIS issue of not rejeting is a likely cause of at least some of the reliability issues and bad reputation reagarding the 951. These guys are maggots !! People bring their skis to make them reliable and this is the kind of stuff that gets done... by Seadoo Shops. Sad.

Thanks for the heads up. Before I even started rebuilding this machine 6 weeks ago I thought that intake system just looked sketchy. I'm absolutely amazed at how easy it was to destroy my motor. But the machine is so much fun to river run on.

I'll research what options for a fix there are. I'm inclined to custom fab a snorkle on the existing intakes that will feed up through the hood and draw air from the dry area behind the gages. No idea how I'm going to do it yet, but it's the driest spot on the machine. Or snorkle as high up as I can under the hood and relocate the hull air intakes somewhere high. Maybe modify the seat shock cover to draw in from between the seat and cosmetic cover under it. Lots of possibilities and 6 months of winter to work through it.

 

[mikidymac]

As for as I have seen there’s only 1 air box and no recall or jetting changes.

I think the dealer might have been thinking about all the issues the white 947 has in the 1997.5 GSX and been confused about the recalls.

 

[mikidymac]

The easiest way to fix the nose water issue is to just plug those big 3” holes in the front of the ski.

It will still get plenty of air through the rear ones like the newer XP hulls.

 

[AKnarrowback]

The easiest way to fix the nose water issue is to just plug those big 3” holes in the front of the ski.

It will still get plenty of air through the rear ones like the newer XP hulls.

Thanks. I want any "mods" on this machine to be clean because the DOO is is really good shape considering the environment it's lived in. My 94 XP is the rat rod.

 

[etemplet]

As for as I have seen there’s only 1 air box and no recall or jetting changes.

I think the dealer might have been thinking about all the issues the white 947 has in the 1997.5 GSX and been confused about the recalls.

Water Injection on the XPs. Some Airbox Mod required a rejet and they didn't do it. He knows his shite enough to screw people and lie about it. Scum as far as I am concerned.

 

[Poormanracing]

Just a side note on this issue. I was talking to a shop owner and what he said disgusted me. Not sure if it was only the 951s that were known as unreliable or got a bad reputation. Apparently Seadoo did an upgrade and paid the shops to perform it. He told me it was a water injestion issue and they replaced the airbox and.... were SUPPOSE to rejet the carbs. They DID NOT REJET the carbs because, he said, Seadoo didn't pay enough for that so all they replaced was the air box. Now to me... THIS issue of not rejeting is a likely cause of at least some of the reliability issues and bad reputation reagarding the 951. These guys are maggots !! People bring their skis to make them reliable and this is the kind of stuff that gets done... by Seadoo Shops. Sad.

The air box recall did require that the carbs be rejected as the new air box is more restrictive and pulled most of it's air from next to the exhaust manifold.as for not rejecting causing reliability issues no way.we had to jet them leaner than stock and it was only one jet size on the mains.on the xps when you swamp them it goes right into the air box makes it's way into the carbs then goes into the return line to the tank.when there is water in carbs or fuel it blocks the low speed side of the carbs and if it can't pull fuel it can't pull oil that is injected at the manifold and the first thing to go is the backside of the piston skirts as some fuel and oil is getting thrown to intake side but not enuff to get to the backside of piston.are you still using the white storage tub that came with the xps and are the seals good

 

[etemplet]

@Poormanracing. DUDE !! Thanks for the explanation. You know your shiznit. Thanks so much for clearing that up. Sounds like what is happening with AKnarrowback's ski. Great info !!

 

[Poormanracing]

I have been working on sea doos since 92 lol worked at a dealer for 15 years then got burnt out but always serviced them then got back into the business 5 years ago at a mariner and now I work part time doing the old skies at my own garage because dealers won't touch them.