2001 Seadoo Sportster LE. Just got it!

[Waterluvr]

I took a video through the port and spread them to a JPG.
This is the piston skirt. What do you guys think?
The other one is better, no so much yellow stuff.
View attachment 26478

So that piston is scored pretty heavily, taking a closer look at the pictures it appears your lower piston ring is stuck from melted aluminum transfer into the piston ring groove. The top ring looks good and is sealing things up for the short term but that could change in a real hurry.

I'd pull that head right away to get a look at the cylinder walls, I'm one of those people that will never recommend just a top end job with new pistons and rings and a cylinder hone on a marine engine here in the US more than a few years old because I have seen so many crank seal leak issues on cases that won't hold hold vacuum or pressure and I firmly believe ethanol is to blame for the rapid deterioration of the crank seals.

In decades gone by we routinely worked on 2 stroke outboards with 20+ year old seals that were holding good as new, that changed when ethanol showed up in gasoline and I have seen numerous crank seals from various manufacturers fail within ten years time on low hour powerheads at an alarming rate. Shocking considering the advances in synthetic oil blends and pure synthetics available and widely in use these days.

It might be different with Canadian fuels, but at any rate an evaluation of the bottom end might show it's still serviceable and a top end kit will restore power and performance for a little bit of time and money. I would rather have my complete engine rebuilt using the existing block and cylinders and head if that were an option to retain the factory compression levels as I understand some popular Rotax rebuilders are known to change some of those things during remanufacturing.

My 787 Rotax still makes compression levels in excess of 150 psi and runs like new yet it's 17 years old now. It's just a matter of time before one of those crank seals starts to leak and lean out the engine. It will probably get pulled and sent up to an engine builder in Northern Michigan over the winter just because it won't take much to make it all new again and get new seals back in the motor. I'd rather be without my motor in February than July when I want to be on the lake.

 

[Bonmotwang]

Just wondering if the rings are there, what was scoring the piston? The RAVE blade?


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[Waterluvr]

Just wondering if the rings are there, what was scoring the piston? The RAVE blade?


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Heat and friction cause it, the source of which stems mostly from running lean. It is the same death that the vast majority of all 2 stroke engines die from unless a rod, bearing or ring lets loose and grenades the internals.

 

[USAF_Pride]

This would also explain why your compression testing showed low numbers. If you are going to keep the boat, I would definitely schedule a winter rebuild project.

 

[Bonmotwang]

This would also explain why your compression testing showed low numbers. If you are going to keep the boat, I would definitely schedule a winter rebuild project.

I agree. Yes, I am planning to keep the boat. Selling this and getting another one is just into another loop for something else unknown anyway.
I will clean the RAVE, and I guess I need to check the Carb settings, the low and high speed screws?

I would like to use the boat 3 or 4 times more in the summer. Do I have to pull the head off right now? I don't think I can replace the piston by myself because of the size of the piston or the size of the cylinder need to match?

What I can do "right away" is clean the RAVE, put the setting to more "rich" if this helps.
Do I need to add oil into the fuel to give the engine extra extra oil

I am waiting for your suggestions.

Again, man, this season has already been a blessing with your guys' help all the way alone. It's been fun boating, also fun dealing with small issues on this community.
I am looking forward to work on the boat especially on the engine to get it working smoothly and top tuned if I am not dreaming.

 

[Bonmotwang]

2001 seadoo sportster RAVE disassembly.

Followed the manual, every step is straight forward and easy. Only thing I noticed is the 10mm hex piston screw is not even hand tight but not loose either.
And I didn't take off the bellow because there is a spring ring hide underneath and pretty tight. I am afraid it will give me hard time to put it back if I took it off.

Here are some photos before cleaning.

This the whole set

This is the two sets

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[Bonmotwang]

Looking at 787 engine's RAVE drawing.

This is my understanding. Please let me know if this is correct.

787 RAVE has a small passage hole for the exhaust pressure coming into the bellow. There is no solenoid control for the RAVE. So it is totally regulated mechanically and regulating all the time.

This hole is blocked in 947/951 engine. A solenoid controlled pipe from exhaust pipe into bellow is doing the pressure job and only working when the solenoid is open at high RPM.

 

[Bonmotwang]

Heat and friction cause it, the source of which stems mostly from running lean. It is the same death that the vast majority of all 2 stroke engines die from unless a rod, bearing or ring lets loose and grenades the internals.

So i guess it has been seized?

 

[Waterluvr]

So i guess it has been seized?

1. You were spot on with your understanding of the differences in Rave valve operation between the two motors, you're getting good at this. I like your enthusiasm for working on the boat and spending family time on the water, you *get it* as I like to say.

2. Pistons that are starting to score on a water cooled motor that's not running to hot or lean rarely seize right away, heat and friction cause the loss of aluminum from the piston walls and those are the vertical lines that you are seeing on your piston in the still frames you were able to capture. By the way that was really neat the way you did that, good catch finding that early on that you need motor work!

What happens as time goes on is that compression will continue to drop due to larger amounts of the compressed fuel and air mixture making it's way past the rings on the intake and power stroke. Also, more heat from the combustion of the fuel is going to make it's way down past the piston dome and into those scored areas accelerating wear instead of making it's way out the exhaust.

At whatever point compression has dropped low enough to really get things leaned out and hot and piston slap begins to occur as bore clearances increase is when it will seize or worse.

On Edit: I need to replace my inspection camera, simply removing the raves twice a season and being able to get a look in there like you did was a brilliant idea and I really want to know what my piston skirts look like now and in the future.

 

[Bonmotwang]

Do I need to pull the whole engine out to do a top end rebuild?
If the engine has to be pulled out, then I would like to do more than top end.
If the whole engine came out, I want it go back like a new:-D


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[Bonmotwang]

For the inspection camera. I was using my iphone. Get the camera app to take photos with flash light on and use big button feature. I just laid the iphone on top of the rave port and turn the flywheel by hand step by step and touch the iphone screen at the same time.
A camera app with timer will do a even better job I think.


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[Waterluvr]

Do I need to pull the whole engine out to do a top end rebuild? No, but it would be much easier to do that work properly and get everything back together the way it needs to be if you do. I would remove the engine for a top end job if it were my boat and the engine only had a very minor issue that warranted doing that, it's tough to get piston rings to behave and slide up in the cylinders while you're hanging over the side of the hull in pain

If the engine has to be pulled out, then I would like to do more than top end. I get that, pull that motor and run it over to Full Bore in Alpena, MI and let them make it better than new. When it's done, drive down to my place and we can drop that in and make sure it's aligned perfectly and tuned the way it needs to be. Those little ones of your's don't need to worry about being without the boat next year

If the whole engine came out, I want it go back like a new:-D


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I really couldn't agree more with the wanting it better than new part, summer is to short and the kids grow up to fast to waste time with anything less dependable.

 

[Bonmotwang]

Full bore was part of my plan for the top end. But I guess I can just ship it back and forth.
Is there a practical way to inspect the bottom end?
I was doing some checking last night: I was turning the flywheel back and forth by hand and listen "into" the engine.
When the flywheel going back and forth I can hear metal hitting metal sound. Is it normal because of the play between gears?


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[Waterluvr]

Full bore was part of my plan for the top end. But I guess I can just ship it back and forth.
Is there a practical way to inspect the bottom end?
I was doing some checking last night: I was turning the flywheel back and forth by hand and listen "into" the engine.
When the flywheel going back and forth I can hear metal hitting metal sound. Is it normal because of the play between gears?


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Hard to say really, some of those types of sounds are heard when 2 stroke engines "death rattle" right before bearing cages let loose and bad things happen at high rpm's. Gears meshing shouldn't make sounds that make you think of grinding or rough surfaces coming in contact with each other.

 

[Bonmotwang]

Hard to say really, some of those types of sounds are heard when 2 stroke engines "death rattle" right before bearing cages let loose and bad things happen at high rpm's. Gears meshing shouldn't make sounds that make you think of grinding or rough surfaces coming in contact with each other.

It only happens when flywheel switching directions. That is why I think it is the slack in the system.


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[Sportster-2001-951C-Stock]

The 951 is known for broken piston skirts and grenading, so look carefully for cracks in your piston skirts. Unfortunately with low compression and probably a seized ring it needs to be rebuilt.

So will you wait for the engine to grenade and pick up the pieces from there or tear it down first? I dunno, an engine grenade might be a valuable lesson for the young ones about what happens when an engine is "abused"?

 

[Bonmotwang]

I guess I need to do it right away and hope I can still catch part of August? Full bore does the full engine rebuild for about $1400...


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[Waterluvr]

The 951 is known for broken piston skirts and grenading, so look carefully for cracks in your piston skirts. Unfortunately with low compression and probably a seized ring it needs to be rebuilt.

So will you wait for the engine to grenade and pick up the pieces from there or tear it down first? I dunno, an engine grenade might be a valuable lesson for the young ones about what happens when an engine is "abused"?

They do make some pretty spectacular sounds at 6K rpm's when the crank bearings and rods let loose after the pistons melt and come raining down the holes lol! -Not that I endorse that sort of thing mind you, but "unforgettable" for sure.

I wasn't aware the 951's were known for cracked skirts, that's an extra helping of bad for motors known to have those issues. Sooner than later would be the prudent thing to do in this case for sure.

 

[Sportster-2001-951C-Stock]

In the interest of expediting the process, perhaps one option is to pay the core charge up front then return your unblown core for credit? I guess the rebuilder's situation can vary depending on shelf stock but maybe this works in your case? The risk is the cases may not be in pristine condition but a good rebuilder won't try to pass off that kind of garbage.

 

[Sportster-2001-951C-Stock]

I wasn't aware the 951's were known for cracked skirts.

Yeah, I think one of the failure modes involves pieces of skirt breaking off and bouncing around in the crankcase. This kind of skirt failure is consistent with excessive bore clearance. Not sure if this precipitates a rod letting go or which is the most common root cause but accounts I've read seem to grenade through the case while running in the upper band mostly.

Hard to say what might happen if he keeps running it like this but I'd bet a dollar BONMOT's motor has aluminum smeared up and down the cylinder wall from several partial seizure events and it probably won't take too much longer before something catastrophic occurs.

I really need to find some time soon to look mine over, haven't even checked compression this year, it's just been splash and go. I think the RAVES may be sticking again, so that would provide the perfect excuse for taking a peek.

 

[Bonmotwang]

In the interest of expediting the process, perhaps one option is to pay the core charge up front then return your unblown core for credit? I guess the rebuilder's situation can vary depending on shelf stock but maybe this works in your case? The risk is the cases may not be in pristine condition but a good rebuilder won't try to pass off that kind of garbage.

Looks like suddenly I got into a big decision process now.
Anything that I can do more or test for more background check, or it is obvious now.

A few options floating around in my mind right now based on what I know and I don't:

1) Open the head with the engine in place. Take a look into the cylinder wall to see the condition.
Do I need a gasket kit for doing this if I decided to put the head back?
With the head off, can any low end inspection could be done?

2) pull the engine out. Send the top end to fullbore ($400) and put it back by myself.
The question is how do I know if the crankshaft and counterbalance shaft and gears are ok.

3) pull the engine out. Have fullbore to do the whole rebuild ($1400) and put it back by myself.
My question is if I spent this $1400. Does it mean I have an as new 947 engine? And if I do proper maintenance, it will last another 6 or 8 years?

I have read through fullbore's long web page about their beautiful work and difference between their rebuild and SBT ones.
Sounds like for $1400, I can get a worry free shiny pretty engine. Did I read it right?


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[Bonmotwang]

Yeah, I think one of the failure modes involves pieces of skirt breaking off and bouncing around in the crankcase. This kind of skirt failure is consistent with excessive bore clearance. Not sure if this precipitates a rod letting go or which is the most common root cause but accounts I've read seem to grenade through the case while running in the upper band mostly.

Hard to say what might happen if he keeps running it like this but I'd bet a dollar BONMOT's motor has aluminum smeared up and down the cylinder wall from several partial seizure events and it probably won't take too much longer before something catastrophic occurs.

I really need to find some time soon to look mine over, haven't even checked compression this year, it's just been splash and go. I think the RAVES may be sticking again, so that would provide the perfect excuse for taking a peek.

What is the minimum I need to just open the head, post a few picture here and put the head back?


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[Waterluvr]

You read it right, take care of that engine and you're going to get more than 6-8 years out of it, it's already made it to the 13 year mark.

Removing the head is easy enough to do, all it is going to allow for is cylinder wall inspection plus whatever portion of the ports are visible but that will be very telling if there's aluminum transfer all over it. Easy does it on the head bolts if you get one that doesn't want to back out.

Also, you might want to start soaking the engine mount bolts right now for a day or three and see if you can get those to turn a little and keep applying penetrant. Those can be tricky to get out without breaking one.

 

[Bonmotwang]

You read it right, take care of that engine and you're going to get more than 6-8 years out of it, it's already made it to the 13 year mark.

Removing the head is easy enough to do, all it is going to allow for is cylinder wall inspection plus whatever portion of the ports are visible but that will be very telling if there's aluminum transfer all over it. Easy does it on the head bolts if you get one that doesn't want to back out.

Also, you might want to start soaking the engine mount bolts right now for a day or three and see if you can get those to turn a little and keep applying penetrant. Those can be tricky to get out without breaking one.

Do I need a new gasket set if I decided to put the head back?

When i take the head off, do I need to or can I take the whole cylinder off too?


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[Sportster-2001-951C-Stock]

I think the best way to move forward is by gathering materials/tools/parts in preparation for a reman engine swap, if it were me I don't think I'd even bother removing the head before I ship it off. Those crankcases in servicable condition are worth considerably more than they will be with holes punched through them and the bottom end is probably too tired anyway by now.

$500 here and $500 there trying to nickle and dime your way through will add up fast and I predict will end up costing you more than just biting the bullet, IMO.

Get the no-fault warranty if you can, 2 years is better than just one, break it in as per instructions, align it properly and rebuild the carbs, make sure they're clean where it counts esp. "bypass" holes (transition ports). While they're apart I suggest throwing the next size up low speed pilot jets in those carbs if they were showing any indication of poor throttle response due to lean hesitation, based on what I found with mine they're calibrated too lean IMO.