Sea-Doo Tow Tap: Do You Need One, and How Does It Actually Work?
If you’re towing your Sea-Doo behind a boat — deliberately, or because it’s broken down and you’re getting it home — you need to stop water flowing through the engine first. Tow it slower than about 5mph and you’re generally fine without doing anything. Go any faster than that, or tow it for any real distance, and you want the cooling flow stopped.
To understand why, you need the quick version of how your Sea-Doo’s cooling system works.
How Sea-Doo’s Cooling System Works (The Quick Version)
Water injection point after the exhaust manifold, shown with the waterbox removed
When the ski is running normally, water gets drawn in your intake and compressed through the jet pump to give you thrust. That same water is also routed through the exhaust system and intercooler (on supercharged models) to cool it. Even on a Sea-Doo with a closed-loop cooling system, raw water from the lake or ocean still does the job of cooling the exhaust.
As water moves through the cooling jackets around the exhaust manifold, it picks up heat. Further along, near the end of the exhaust manifold and the start of the waterbox, water is injected into the exiting exhaust gases to cool the parts of the exhaust system that aren’t water-jacketed — the hoses, the sound suppression baffles, the outlet. Those components would melt without that injected water. While the engine’s running, the exhaust gases carry that water straight out with them, so it never has a chance to build up. You’ve probably seen this yourself: give the ski a rev on the trailer and you’ll see a burst of water blow out the back — that’s excess water clearing out of the waterbox under exhaust pressure.
What Happens When You Tow Without One
When you’re towing, the hull’s being pulled forward through the water, so the jet pump is still drawing water in and pushing it out through the nozzle — nowhere near the pressure of a running engine, but enough to pressurise the cooling system and push water through the engine and exhaust exactly like it does when running. The problem is the engine isn’t running, so there are no exhaust gases to carry that injected water back out. The waterbox starts to fill.
Past the waterbox, the exhaust hose usually runs up and over to the other side of the ski before dropping back down to the outlet — a deliberately high routing designed to stop water siphoning back in while the ski’s just sitting in the water. But under tow, with the waterbox filling from below, water takes the lowest path available. That’s back toward the engine. Keep towing, and the exhaust system and eventually the engine itself will fill with water.
This is exactly what happens when you flush your Sea-Doo without the engine running, too — same mechanism, same result if you leave the hose on too long with the engine off.
How a Tow Tap Actually Works
A tow tap is a small ball valve fitted into the cooling line. Turn it, and it shuts off water flow through the engine entirely — so none of the above happens, no matter how far or fast you tow. It’s a straightforward install, either done yourself or by your local workshop. The only thing that matters is getting it into the correct cooling line.
On models with tighter engine bay access, like the Spark or new ST3 models with limited access from the large deck cover, an extra length of hose can be added to relocate the tap somewhere you can actually reach it from outside the hood.
The Screw-Clamp Alternative
If you don’t want to permanently fit a valve, you can carry a hose-pinching tool instead — a large brake line clamp or a screw clamp works fine. Clamp it onto the correct cooling hose whenever you need to tow. The trade-off is you need to know exactly which hose to block, and have the tool with you when you need it. A permanently fitted tap removes that guesswork.
Pro Tip: Don’t Forget to Turn It Back On
Here’s a habit worth building: when you shut the tap off before towing, put your ignition lanyard in with it — clip it over the valve, or tuck it against it, whatever works. When you arrive and go to jump on the ski, you’ll have to go looking for your lanyard, and that’s exactly the moment you’ll be reminded to turn the water flow back on. It’s a small thing, but it’s what stops an overheat that would otherwise ruin the rest of your trip.
Going Further
A tow tap is a simple, cheap fix for a problem most owners don’t think about until it’s already happened. If you’re getting into more of your own maintenance — cooling system checks, flushing technique, what else to look at when something’s been sitting or towed — that level of detail is covered properly in the New Owner Guide and DIY Servicing courses.
If a tow or a flush gone wrong has left you chasing a fault code or a no-start, the Fault Codes guide and DESS Key article below are the next places to look.