1999 Polaris Pro 785 purchase

[Matt Braley]

Subscribed. I recently bought my first Pro 785 but have not started addressing it's needs yet. Pics please.

[Sage18]

I’ve worked on Polaris & Sea-Doo jet skis for years replacing many parts, diagnosing problems, rebuilding carbs, new top ends, ect. I never worked on a Pro and have never worked on the bottom of an engine. What do I look for if the crank seals are bad? I assume oil or water would be infiltrating into the crank case? Today I talked with the owners son who rode this Pro 785 and he said that he rode it every year on a semi private lake so he didn’t register it since 2013 but it was put on the water every year and said he never had problems with it but lives out of state so he didn’t want to mess with trying to sell it. He said “being 20 years old it isn’t worth much” it’s only showing 43 hours of run time on it by the way

I put fresh gas (with some oil in it), new plugs, cut the spark plug wires back, and I fired it up and it seemed to run great! I saw the exhaust valves moving in and out with throttle response. I shut it down after a pop or two of the throttle. Checked compression and it was 115ish each cylinder. It has the old tempo lines in it. So fuel lines and carb rebuilds are first in my list. Can you just replace the rings in these thing because the compression is a tad low? Can I run it at 115 psi? It seemed to start right up great.

Also are there filters in the cooling lines for the exhaust? I seem to remember some on my other machines exhaust barbs? There are tempo lines on the exhaust cooling hoses as well. Do these operate at a high pressure can I just use my 1/4 fuel line when I replace them? I see there are check valves on all three pipes? Do I keep those in place or remove them?

Any more info is appreciated. Thanks

[Sage18]

Here are some pics of the existing ski. Fuel lines, carb rebuild kits are on the way. Looks like it has the wrong battery in it and definitely old fuel lines...

[Sage18]

Does this look like the stock MDF? I saw in a previous post that someone had a carbon fiber plate for behind the MDF. Where can I get one?

[Sage18]

The second one was gone the next day.... it would have been nice to have two!

[Sage18]

Anyone have a shop manual that I can buy to reference for working on a 99 785?

[K447]

... shop manual ...

Lots of useful info here and here. Click around to find what you need.

[Sage18]

Thanks k447. The pro has 115 psi thoughts on running it? Trying to get my ducks in a row on what to do after carb rebuild and fuel lines.

[sdlvx]

If it's an even 115 it's probably a bad reading, bad gauge, etc. As long as they are even you are fine to see how it runs as far as compression is concerned.

[Sage18]

They were 111, 114, 115 I believe. Maybe my gauge is bad. It’s just one from auto zone. Is that too low to operate it normally Or is it ready for new rings? Can you just do rings on these? Or a full top end? Water temps are getting low around here so I don’t want to put it in cold water, it’s 50 or close to it. One of the guys said don’t operate it in water below 60.