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Rotax 717 won't turn over

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splishy

New Member
I've got a twin 717 rotax Challenger and the right engine won't crank. I've removed the spark plugs, starter and the rear impeller to make sure neither of those are causing it to stick. When I try to turn the flywheel manually it only wiggles about 10 degrees before stopping abruptly.

What should I check next or what else could be causing the issue?
 
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are you trying to manually turn the pto with the spark plugs in or out? if the plugs are in, and you have really good compression it will be difficult to rotate 360 degrees. pull the plugs and try rotating it again. If your battery is bad it will have a hard time cranking. Check all your grounds....pull them apart, sand off any corrosion. Is this a new to you boat? Do you have a history with the boat? Was the engine cranking and starting previously?
 
Thanks for your help! I'm trying to crank by hand with the plugs removed. Also to clarify, it doesn't have a slow stop on either side like a compressing feel, but instead feels like a physical "clunk" when I'm trying to turn the PTO almost as if something is in the way. At first I thought that maybe I had a stuck rock in the impeller, but once I got home and removed the impeller that wasn't the case.

The issue that came up was when I was on the lake, my left engine started fine and my right engine (which used to work fine) wouldn't start. I tried starting it a few times and then it worked for about a minute and then stopped abruptly. I then docked the boat as I couldn't start the engine again after that since it wouldn't crank.

I got this boat last summer and the right engine (this one) had worked fine all season long until that day. The left engine gave me a lot of problems over the season, but those are all fixed now.
 
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If the pump and driveshaft is removed, spark plugs out, the pto should rotate very easily. if you have a scope you could put it down the spark plug hole to see if the pistons are moving up and down as you rotate the engine the little bit you are able to do. or put a straw or something into the hole, rest it on top of the piston to see if it goes up and down. If they are not moving you could have thrown a rod. I guess there are no visible holes in the case (i had one that i could not see a big hole at the bottom of the engine when i was purchasing a boat once)? or oil just spilling out into the hull?

I suppose something could have fallen into the carb and blocking the valve, but it sounds more sinister then that. I think unfortunately it is time to pull the engine.
 
Thanks for the straw tip, I'll give it a shot. I checked inside the spark plug holes with my scope earlier and didn't see any concerns, but didn't think to see if the pistons themselves were moving while trying to rotate the PTO.

If they do rotate, what would I want to check next?

What would I specifically be looking for when I pull the engine? Part of me is so frustrated from this process that I want to swap it out with a rebuilt one, but the other part of me feels like it could be something simple (although it hasn't proven to be the case yet).

Also silly question but how do I check to see if the engine is waterlogged? I don't think that's the case but want to rule that out since I drifted away from the dock that day and limped back with 1 working engine. Maybe the intake is just flooded but if so, would it be a sudden stop on the PTO like this or more gradual/compressed feel?
 
if there was water it would be shooting out the spark plug hole while cranking. Again, if you have the pump pulled off and the plugs out the crank should rotate very easily and if there is an abrupt stop internally something is broken.

Before pulling the engine i would pull off the carbs to see if there was any obstruction on the rotary valve just to be sure. from there you could pull the cylinders off while it is still in the boat, but in my opinion if it gets to that point you should just pull the engine out because doing all that work while it is still in the boat is not easy and should really be a rebuild.
 
Thanks for the confirmation and suggestions, it really helps give me an idea where to go next from here.

If I go the route of swapping for a rebuilt engine what should I look out for? I vaguely remember needing to check which brand parts were used (forgot the correct brand to use off hand), but anything else too?
 
Depending out where you are in the world you will get different answers on how to replace your engine. maybe include the general area you are in and you may get some responses in this forum on where to look. i am in ontario and i have heard some good responses from a company out this way. i know of SBT but do not have any experience with them. there may be some engine rebuilders out there that you could try. There are always "rebuilt" engines posted on marketplace but the quality of the rebuild is always in question. you could always try to tackle it yourself.
 
some rebuilders want the core (your old engine) when you purchase a rebuilt one. so hopefully yours does not have a big hole in the bottom from a thrown rod.
 
So typically it is the rotary shaft gear that strips and locks up the engine.
As said above, pull the carbs then the rotary valve cover and go from there.

SBT engines and parts are very low quality but if you can't rebuild it yourself it is one of the few options. Best bet if you are able is to rebuild yourself and send the cylinders out for machining.
 
They were just a bit more than rebuilt at the time and I could get one in 4 days with no core. :D I have two brand new WSMs for 717s waiting to be built. I restored the skis and sold them so I can't say how long they last. I liked them.
 
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