First time posting here in a couple of years or maybe first ever. I have a 96 Challenger and recently the thrust bearing seized up and the center of the pump body got badly damaged. No damage to the shaft or impeller. I shopped around and found a pump body on ebay that looked identical. Now I wonder if it was. The pump body I bought came out of a 1998 Sportster 1800. The only obvious difference between the two pumps is that the water tube on my challenger was too big to fit into the used pump. There was plenty of material, so I drilled it out and tapped the next size larger pipe thread. But now when I torque the pump down the engine will not spin on the starter. If I back the four nuts off slightly, still snug but not to spec then the engine will spin right over. What I wonder is if the is an actual pump body difference, like the distance from the front of the body to the front of the impeller is different? Has anyone encountered anything like this? I am tempted to add washers between the body and the boat to increase the clearance.
Used pump body when torqued down engine won't spin
- Thread starter tbacon
- Start date
mejim707
Active Member
I don’t think you should add washers since these should seal against the hull or you’ll get cavitation.
But this is a good question, even when aligning the engine, one thing I never see mentioned is the clearance from the PTO to the pump when it’s full attached. Or maybe I always miss that part?
When you use the alignment tool they only talk about the pole seating in the PTO smooth. But the PTO to pump space isn’t mentioned?
If you intend on using this pump, you may need to readjust the actual engine to pump space by loosening the engine mounts then bolt and torque the pump. Don’t use the starter but try to rotate the PTO a little by hand. If you can rotate the PTO then technically you could mark the mounts to get the clearance right then realign the engine not allowing the engine to move past those marks.
To me this seems like a lot of work to use a mismatched pump but maybe it’ll work. But definitely don’t use the washers. You want the pump to fully mate with the hull and pump gasket to avoid cavitation.
Have you checked that the bolt placement on your old pump and new are identical? If the bolt pattern is even a little off then your alignment will be off. In fact, why did the old pump seize? Perhaps the engine alignment is way off in the first place resulting in your pump failure.
mejim707
Active Member
Actually, just thinking about this more, there has to be a reason your old pump failed. Have you checked if the engine alignment is good? Do you have an alignment tool for this?
I would 100% start there.
Even if the boat was running, it’s possible the alignment is off. Before I replaced my engine I checked the alignment of the old engine and it was WAYYY off. You could have the same which could cause a pump to seize and fail.
I would 100% start there.
Even if the boat was running, it’s possible the alignment is off. Before I replaced my engine I checked the alignment of the old engine and it was WAYYY off. You could have the same which could cause a pump to seize and fail.
This has turned into an experiment now because I don't have the patience to deal with it at the moment. I did shim the pump, but I am not the first to do so. It had 4 washers of 2 different thicknesses when I removed it.
Some history regarding why the pump failed. I bought this boat as a fixer. Someone had redone the top end previously but was not careful about the wrist pin bearing pins and some ended up in the crankcase. One found its way through the intake and into one of the cylinders. The head was off when I went to look at the boat and the owner was up front about that. I put new oversized pistons and cylinders on it and got it running. The boat performed excellently but had an annoying rattle at idle which I learned from this forum is corrected by putting a anti rattle kit on. I ran it a few times before I put the anti-rattle kit on but not much due to an oil leak. Before splashing the boat for the first time the next season I put the anti-rattle kit on. When I removed the existing cone, it was full of water. The o-ring was out of place, so I assume that is how the oil got out and the water in. I decided to take my chances on that to see how it would sound with the anti-rattle kit and oil in place knowing that the bearings may have been damaged so I would keep my eye on it.
In the meantime, I started having trouble with the boat quitting. It would always start back up. This issue also resulted in limited use of the boat eventually being solved by a new key post. Then after that the boat started having issues staring. Would have to press and hold the start button a couple of seconds before the engine would rotate. I think this was the first warning of pump issues with it being "stuck" due to bearing issues. I mistakenly diagnosed that as a start solenoid (mag switch) and replaced it and that seemed to make it better.
The final failure occurred as we were headed to our favorite island dock. We have a big boat that we cruise on and like to bring the seadoo along. Sometimes we tow it and others my wife drives it. The day of the failure I was headed out on the big boat ahead of her. I expected her to blast past me, but she didn't. Eventually she called to say she was having trouble. The seadoo would not go up on plane, it would try to but then even though at full throttle the engine would slow. I am certain that is because of the trauma the pump was going through. I turned the big boat around and went back to offer a tow, but she said she just wanted to be in front of me and would continue on. That was the big mistake, I should have insisted on the tow as at that point the pump may have been salvageable. All of a sudden, she blasted ahead making it seem like whatever was wrong corrected itself. About an hour later the final bell tolled for the pump and the seadoo was dead in the water. I caught up and towed her to the dock.
I thought maybe the pump sucked something up into the pump but that turned out not to be the case. What happened was the thrust bearing in the pump completely disintegrated and eventually the shaft seized on the body and when it did it tore the inner part of the pump partially loose from the outer part.
I was going to replace the pump with a new one from SBT for under $500. But I found a used one on ebay for $300 and went with that. The pump dimensions are no different than the previous pump dimensions. It turns out the pump was not binding due to the shaft binding after all which I discovered as I was pushing the collar back to position it against the graphite ring with the shaft sliding back and forth quite a bit, maybe 1/4 inch. Now I suspect the binding was caused by the wear ring protruding too far and then when torquing it down it would warp and bind on the impeller. As I torqued it down on the studs it took several retorques around each nut before it all settled in. Later with the pump back out I noticed the new neoprene ring was sliced by the wear ring. I could see an arc cut in the ring about 3 inches long along the top. I did notice the wear ring was not fully seated when I was inspecting the pump before install, but I thought I got it fully seated before the pump went in. Now I think not.
I experimented with shimming. I'd start torquing the pump down and checking for engine rotation. I added shims until it would no longer bind when fully torqued. That took 2 washers on the bottom and 3 on the top.
I am so frustrated with the whole thing now that I'm willing to take a chance on this pump and its shimmed install. I'll keep an eye on it and if there are any signs of any issue, I'll order the new pump from SBT and see how that goes. Either that or pull it, replace the wear ring and see if that allows the pump to mount without the shims. I am pretty sure I shot myself in the foot trying to save a couple hundred dollars on this used pump. Won't be the first time a small savings turns out to a bigger expense in the end. I give it a 50% chance that this pump is going to work. I leak tested and no leaks and I'm confident if it fails it won't be due to bearing issues. More likely that it fails due to the neoprene ring failing. I am aware that there may be an alignment issue with how the shaft sits in the impeller if in fact it is the wear ring being slightly cocked which required more shims on top. I'm not sure how I will be able to detect an issue from that. Maybe it would be more stress forward bearing in the pump, but I don't think it's going to be off enough to make any difference. Will see.
mejim707
Active Member
Sounds like you've had a tough experience with it. But stick with it because these boats are not only fun but people really like then.
I will say checking the alignment just requires the tool from SBT and it's very easy to do. It's good to have the tool in general. Based on the warping of the wear ring, uneven shimming and the cut in the neoprene seal and so on it sounds like the engine is not aligned.
Doing the alignment is easy, with the pump off and the alignment tool mounted, try to slide the bar into the PTO. If it slides in smooth and fully seats inside the PTO with no resistance or binding then you're good. If it binds or doesn't even interface with the PTO it needs to be aligned.
With the pump and drive shaft removed, you loosen the engine mount bolts, then slide the alignment bar into the PTO. Take your time to get the bar to slide all the way in with no binding. It should be smooth. Then torque the mount bolts down and recheck. If it's still good just reassemble everything. If you need to make tweaks do so until it's right. It doesn't take long, just a little patience then you have peace of mind it's perfect.
When I checked mine for the first time it was way off! The bar didn't even interface with the PTO. The previous owner either didn't care to check or didn't know what they were doing. Either way, it's perfect now.
I got an anti rattle kit for mine as well, and it made no difference. I still have a clunk / rattle at Idle. Listen to this video and tell me if this is what you hear. I've been chasing this for years!
Rattle Sound Video
That's what mine used to sound like. The anti-rattle kit cured it for the most part on mine.
Well, I splashed today. Went out and when I throttled up it bogged down doing so exactly the way my wife explained it. I think the pump failure was coincidental and not related. I gave up for today but tomorrow I am going to pull the plugs to get a look at them and do a compression test. Found some posts indicating rectifier could cause this issue but that makes no sense since its part of the charging system, not the ignition system.
I think my alignment is good. I could easily rotate the flywheel other than compression, no binding. Good info on the alignment procedure though. I'm thinking maybe in the off season I'll pull the pump, replace the wear ring with an OEM to see if I can then get the pump to install without shims and not bind. I've also got a carb rebuild that I already wanted to do, was actually going to get new carbs but there is an excellent highly detailed set of instructions a major member of this site put up.
Just a fyi, the pump to shoe interface should never be shimmed as this does not put enough pressure on the shoe to seal the wear ring to the shoe.
The only ting that gets shimmed is the shoe to hull and engine to engine mounts.
The driveshaft should have plenty of clearance in the PTO and the impeller and is why it uses the rubber bumpers. There should never be enough pressure on the driveshaft bumpers or impeller and PTO to cause binding. You have something wrong.
Are you sure there are not some old driveshaft bumpers stick in the PTO or impeller?
The only ting that gets shimmed is the shoe to hull and engine to engine mounts.
The driveshaft should have plenty of clearance in the PTO and the impeller and is why it uses the rubber bumpers. There should never be enough pressure on the driveshaft bumpers or impeller and PTO to cause binding. You have something wrong.
Are you sure there are not some old driveshaft bumpers stick in the PTO or impeller?
Thank you for weighing in Miki. I am going to pull the pump and replace the wear ring. I believe it was not seated correctly and that created the binding issue as well as the damage to the neoprene seal when it was fully torqued down without any shims. I did get the boat in the water, but it will not get up on plane. When sitting at the dock if I give it full throttle it acts almost like being rev limited but not exactly. It surges between 3500 and 4000 rpm. I wonder if that is due to cavitation with the neoprene seal already being broken, sucked in at least partially. I don't know for sure that isn't an unrelated issue or not. Engine compression is good, the crank is not twisted, disconnecting the rectifier made no difference. Regardless, for peace of mind I'll solve the issue with the pump mounting so that without any shims the impeller still spins freely when fully torqued down. When I got the pump, I noticed when changing the impeller that the wear ring was not fully seated. Whoever replaced it left debris in the pump body that got caught between the bottom of the ring and the ridge/seat that it should be up against. I picked out debris thinking I got all of it and then pushed the ring further in but maybe I missed some and it's still not all the way seated. I think that is the only plausible explanation as to why the pump would seize up when torqued down without the shims. Thinking that the ring distorted enough to bind the impeller which would not take much as the clearance is tight between the impeller and ring.
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