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717 Engine Seized - Help Please

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Prosideus

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1997 GTI doing great this morning and then started bogging down on on mid going to high speed. I gave it a rest a while and got back on it to see what was up. It felt like it was missing a time or two up until on full throttle, the ski just seemed to rev without torque quickly and cut out. Locked up in the middle of the lake. The starter will still engage, and it just clunks without turning the engine. I inspected the impeller and it seems fine.

I have done some preliminary searches, but not confident in associating what I am finding online with what my problem may be. I am not sure how to proceed with next steps for checking out what might be my issue.

Thanks for any guidance.
 
Pull the head after trying to turn the engine over at the PTO. Were you running the stock oil injection?? Need to determine what happened for sure.
 
Using stock oil system, shaft will not rotate at PTO, here is what it looks like having pulled the heads. There is water on the outside cavity of the cylinders, not sure if that is normal.

8f7101babfcb51eab29931a0132fe104.jpg
 
You have to determine what is preventing the engine from turning over. I'll be interested in the input from the guys that have experience with this sort of stuff. What if it isn't related to the pistons at all?
 
I bought a 1996 GTI from a guy and he said he rebuilt carbs and rode it and the motor locked up. I pulled the pump, stator housing, took out spark plugs and the PTO would only turn about 90 degrees. I pulled the cylinders and pistons all looked perfect. Pulled carbs and then the rotary valve cover. One of his carb screws had fallen down and knocked a finger nail size bend in the rotary valve preventing it from spinning. Found broken piece and bent valve slightly and motor spins freely. Just gotta order a new rotary valve.
 
I would pull the pump off and see if it turns over, if not then RV cover to take a peek. If you have to pull motor put the head back on and remove the PTO before you pull the motor.
 
By the piston wash... it's a little lean... but not melted. I'm guessing you have a pump that locked up. Pull it off the back of the hull, and then try to turn the engine over. DO NOT START IT WITH THE DRIVESHAFT STUCK INTO THE BACK OF THE ENGINE AND THE PUMP OFF !! It can swing around and cause damage.
 
SimpleAR, I haven’t discovered it yet. I have ordered the top end gaskets in order to get things back together. As Snikwad and Dr Honda recommend, I will be removing the pump. Appreciate the guidance. Will update when I have something more, or ask for more help.
 
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Good news/bad news. Good news is that the jet pump is seized at the impeller. Will start researching how to get that addressed. Bad news is that I would have rather not taken apart the top end of my engine to discover that. I have the head cylinders off and will be putting new gaskets/seals on the rebuild. Do I need new piston rings or can I use the same ones? They look pristine.
 
Prosideus said:
Good news/bad news. Good news is that the jet pump is seized at the impeller. Will start researching how to get that addressed. Bad news is that I would have rather not taken apart the top end of my engine to discover that. I have the head cylinders off and will be putting new gaskets/seals on the rebuild. Do I need new piston rings or can I use the same ones? They look pristine.
Click to expand...
You should be fine to reuse them if they are pristine, although I would recommend throwing new rings on and doing a quick hone to the cylinders as it is fairly cheap very easy and will help with compression.
 
Similar issue I had removing the PTO flywheel from the crankshaft. Try a bigger vice and bigger tools, I had to go to a heavy maintenance shop and clamp in the 50 lb vice with a 3/4" socket breaker bar with a 4 ft pipe, popped loose with little effort. I was bending the 1/2" bar at home and applying heat wasn't working. Same 23mm spline tool can be used on both ends of the driveshaft, impeller and PTO flywheel side.
 
GGuillot said:
Similar issue I had removing the PTO flywheel from the crankshaft. Try a bigger vice and bigger tools, I had to go to a heavy maintenance shop and clamp in the 50 lb vice with a 3/4" socket breaker bar with a 4 ft pipe, popped loose with little effort. I was bending the 1/2" bar at home and applying heat wasn't working. Same 23mm spline tool can be used on both ends of the driveshaft, impeller and PTO flywheel side.
Click to expand...
A chain wrench is much better on the PTO as you can strip the splines when they are super tight.
 
So the answer is....the impeller is not coming off. Took it to somebody who does it for a living and it isn’t coming off. Bought a replacement jet pump and will be installing that instead.
 
Something break? did the splines strip? Did the person you took it to have a minimum 4 foot cheater bar, impact hardened 3/4" socket tools, and a massive vice? a 6" vice and 1/2" tools with an 18" bar is not going to cut it, no matter how much heat and penetrant you throw at it. I've been through this...
 
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Nothing broke but the amount of time I was willing to allocate to the effort. Replaced the jet pump, reassembled the engine, and the thing fired right up. Runs great in the drive way. Taking it to the lake this afternoon to see how it does.
 
Final post on Seized Engine.

First of all, it was not a seized engine. It turned out to be a seized impeller.

The advice to tear into the engine was completely wrong as a starting point. That was on me for being impatient.

After unsuccessfully attempting to turn engine by hand at the clutch-flywheel, I should not have pulled the head cover.

Second thing would have been to remove the venturi and the impeller housing, separating it from the drive shaft and allowing to separately check both the engine and the impeller.

In my case, the impeller housing was seized. At this point the engine would have turned just fine at the flywheel.

The circumstance I uncovered was that the impeller cover had come off at some point and I never realized it. That allowed water and subsequently rust to set into the impeller shaft bearings which caused them to fail and seize.

After several attempts to remove impeller from the impeller shaft, I took the impeller housing to a place that deals with these things for a living, and they could not get the impeller off. What I also learned is that the aluminum housing on the pump is a less than optimal design.

I replaced the impeller housing with a newer one that has brass housing and vanes. I bought it used for $250 with new ring and impeller.

After reinstalling everything, including reassembling the top half of my engine, the sea doo performed perfectly at the lake today.

Other items maintenanced:
Replaced rubber bumpers at ends of driveshaft.
Replaced graphite ring and stainless steel ring on driveshaft, along with rubber seal rings (interesting design that keeps the water out)
Greased the shaft at the flywheel and impeller.
Replaced oil lines and filter.
 
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