Polaris SL 750

[Skexies]

SeaLion:

Ooof. 3/4 throttle seizure bug, you are not going through pistons I hope?

Main jets not large enough? Thought 3/8 - 3/4 throtle was main jet 3/4 to 4/4 was high speed adjuster teritory.

I'm sure you have more knowledge on the topic... but I'm quite curious.

-Skexies

[Skexies]

On another topic... anyone ever install sponsons on a non-oem SL?

I'm going to give this a try, oh boy does this look like a fun job. I'll have to give it best guess for location. :|

-Skexies

[SeaLion]

I put the stock Polaris 24" sponsons on my SL750. I also elongated the holes (up and down) to make them adjustable. The kit came with an awesome and simple to install hardware kit that you were able to install the sponsons from the outside and not even have to remove the seat. They were special inserts and they work great. The kit also came with a template. I would personally go for adjustable blade sponsons (that is what I put on my SLX) but the hardware that came from Polaris is the way to go to mount them. All aftermarket sponson made do not come with what you need to mount them on a Polaris that didn't originally have sponsons. You can always go the bolt and nut route by cutting the foam out from inside the hull and reaching in to get the nuts on but that is a major pain in the butt. I did 2 Sea-Doos for my buddys that required this and it was not fun at all.

As far as my 3/4 seizure, I just replaced the rear piston and rings and put the engine back together. I rejetted richer and installed 2 new pulse fittings (one on the front cylinder and one on the rear cylinder) to feed each of the 2 fuel pumps. I also by-passed my fuel valve. If it happens again, I can at least rule out any sort of fuel delivery problems.
The funny thing is that at full throttle the ski runs all day but as soon as 3/4 is sustained then it's shut down time [img]smile.gif[/img] . No biggie because the rear piston is a piece of cake to replace without having to even remove the exhaust pipe or ex. manifold.

[Skexies]

Wow... sweet...

I have the polaris "pro" sponson set now... but I think I'm going to cut the foam to be safe.

I read something about 3/4 lockups... ah there it is... [paste]
Mid Range "Torque Peak" Seizure -- This type of seizure is becoming much more common on modern pwcs. The newer boats have ignitions that are very retarded at idle speeds, then reach their advance peak around 6000-6200 rpm. After the peak advance, the timing retards slightly as rpms escalate. The rpm where ignition timing reaches maximum advance is usually the "torque peak" of the power band. That means that the engine is generating more sheer torque, per revolution, than at any other engine rpm. If your carburetion has an extreme lean condition in the mid-range, you can ride full throttle all day long. However the first time you release the throttle into that lean middle range, the combination of the lean mixture, and the heavy timing advance, can create detonation that will result in a swift piston seizure. The rider seldom suspects a lean mid range, and begins looking for other gremlins (air leaks, etc). It bears noting that a prop with too much pitch can cause exactly the same problem. The higher pitch will cause the rpms to be significantly lower (closer to the torque peak) at full throttle. The lower rpm number means more advanced timing, at full throttle, that can (once again) result in detonation ... and seizure.

Dunno if that helps...

Take care,
-Skexies

[ April 25, 2001: Message edited by: Skexies ]

[UniBougie]

Hello all,
I am in search of the elusive Polaris SL 750 Steering cable ('95 model). Can anyone give me a starting point, besides my local dealers. I am pretty dissapointed in them. As it turns out, niether WaterCraft Salvage or MM Marine have the steering cable in their stock. I'm waiting on Parker Yamaha to respond. Is there anywhere else I should be looking.

[SeaLion]

I am well aware of the scenario and I do think I was a little lean. I am definitely not overloading the engine from an over pitched impeller because I am running a 12/17 Swirl (stock is 15/20) and I am also using an 87mm nozzle opening (stock is 84mm). I need this combination for the 92-93 SL650 dry pipe that I am using to be in harmony with the power curve of the pipe. The other suspect could be my timing curve from the Pro785 CDI that I am using. I needed the higher rev limit of the Pro CDI because the stock CDI kicks in at 6700 and I am turning 6950-7000. Th Pro CDI limiter is at 7800 and the timing is advanced down low but retarded more on top. I should be riding tomorrow and doing some final tuning so I'll see if it was a fuel problem.

[Skexies]

SeaLion: Awesome! Let us know how it goes!
[img]smile.gif[/img]

[Lenchmob]

So how is your ski running Sealion?

[SeaLion]

I did ride that day and of course I had my carbs real fat after jetting higher. My max rpm was 6450 and I started to fine tune and got my peak back to 6900. It was a little choppy and a terrible air day for performance but at least there was no 3/4 throttle seizure. Since then I have not ridden because I am prepping the ski for paint. I will be painting it this weekend. I'm going black with clear coat and some killer flame graphics.