417 Hours on One Pump: What the Klotz Oil Run Taught Us

Our rental Sea-Doos live a hard life. Different rider every hour, all summer, in salt water. So when we wanted to settle the grease-versus-oil debate in a jet pump, we had the perfect test subject sitting in the rental fleet.

Since the video went up, the comments have been the same three arguments on repeat. So let’s deal with them using what’s actually in front of us, not what’s in the manual.

“Grease is better than oil.” Based on what? We ran a rental pump 417 hours on Klotz oil with zero grease in it. Not a garage queen — a rental ski, full summer, salt water, different rider every hour. When we opened it up, everything was clean: bearings smooth, no play, no scoring. If grease is better, show me a grease-packed rental pump that looks that good at 417 hours.

“Why would you even put oil in a pump?” Because the bearing doesn’t read the manual. It needs lubrication that reaches it and keeps working. Oil flows and coats; old grease dries out and cakes up. We didn’t do this to be different. We did it to find out what survives a rental season. Now we know.

“Aftermarket shafts are worse than OEM.” Our teardowns say the opposite. The early failures we see are OEM shafts running OEM grease — that’s the combo that comes in dead. The aftermarket shafts we run, paired with Klotz oil, hold up better. Not because of the name on the box. Because of what we see when they come apart.

Left Shaft (OEM) vs. Right Shaft (Aftermarket)

Nobody has to agree with any of this. Here’s what the teardown showed — do as you please.

The setup: 417 hours, zero grease, Klotz oil only. On June 19, this pump went back into a rental ski filled with Klotz jet pump oil — and no grease at all. It ran the entire rental season. When we checked it, the meter read 417 hours.

Our winning combination

What we found: a pump that didn't need us. No play in the bearings. Spins smooth. No noise. The red Klotz oil was sitting right where grease normally goes is supposed to go, doing the job. Everything felt perfect, so we left it alone — pressing out a good bearing just for the camera would have meant a rebuild for no reason.

Why a rental ski is the real test. This wasn't a lab experiment or a garage queen. It was 417 hours of rental duty, the hardest life a pump can live. If the oil was going to fail, it would have failed here.

The question everyone keeps asking: how much oil, and how exactly do you do it? Below is the step-by-step guide:

If your pump doesn't feel like this one did — any play, any roughness, any noise — don't run it and hope. Send it in for a mail-in rebuild at https://www.jetandpropshop.com/shop and we'll bring it back to factory specs.

Bottom line: 417 hours, zero grease, bearings feel brand new. The oil earned its keep.

Want to run the same setup?

I stock these shafts too — call the shop at (410) 973-2890 and I'll beat Amazon's price.