Coolant Hoses

Time: 1 hr

I roughed in the two main cooling hoses that run to the water cooler. TAF supplies some custom made hoses that look pretty good, but I’m trying to use the least amount of rubber hoses I can for reduced maintenance. I found some super flexible 25mm silicone hoses that can be used with coolant and meet the specs in the Rotax manual (up to 257º F and 73psi burst). I ordered the hoses from a UK company called Viper Performance which had both reasonable prices and shipping. Shipping via DHL only took a few days so not too bad. I also order a few short bent hoses. The thinking was to use the bent hoses for maybe the tight 90 out of the coolant housing on the top of the engine and then some 45’s into and out of the water cooler. I found though that the super flex hose seems to work better because it’s able to bend in multiple directions so I ended up just using that for now. When I get the water cooler I’ll see how it works on that end. I also found some hose clamps on Amazon that expand and contract as the connection heats up. It’s probably doesn’t matter so much with this smaller hose, but I figured it can’t hurt. The only downside is that the clamps are a bit heavy and bulky.

To get the rear hose in you need to turn the water inlet on the back of the engine to point to the right side rather than the factory install left position. There are actually six different angles the inlet can be position. I ended up using the right facing 70º position (slightly pointing up). The 105º position (slightly pointing down) would have worked as well, but I didn’t like how tight the hose was bent right at the fitting. Moving to the slightly up pointing position allowed the hose to pass through with a bit more space and a better angle. I was kicking myself for not doing this prior to putting on the engine, but it seems like the easiest way to get the hose on the inlet fitting was to remove the fitting and put the hose on then install the fitting. Now that made the hose install easier, but then installing the fitting back with the hose attached proved to be a bit challenging. Though with this in mind I figured it really doesn’t matter if you do this before or after mounting the engine. I suppose if you have the coolant hoses then prior may be better.

The 25mm silicone hose attached to the coolant tank on top of the engine. I was surprised at how flexible the hose was and how well it all fits in the small space there is to run the hose. I thought this was going to be the hard one, but it turns out the hose only took a few minutes to run through. The hose on the back of the engine for the inlet was a bit more involved.

The hose runs down the left side of the engine. I’ll need to find points to secure it.

This is the hose on the inlet on the back of the engine. This took some maneuvering to get in. It’s a bit of a pain trying to get the two allen bolts that hold the inlet onto the engine since there’s not much space to work (but when is there ever?). The inlet is in the 70º position which seemed to work the best.

NOTE (6/8/2019): So a few days ago while I was cleaning up the garage I found a large O-ring on the floor. Guess where that came from? Be careful when you remove the hose inlet there’s an O-ring in there and if it fails out make sure you put it back. Also make sure to use the holes that are across from one another, I almost put it make together with the bolts in different holes and it seemed to fit OK, but it definitely would have leaked.

It’s a bit close to the exhaust, but the exhaust will be wrapped and I’ll put on some thermal wrap on the coolant hose as well.

Just a shot of one of the bent hoses I purchases and the clamp.TAF supplied some fittings to connect hoses together so if I end up using these hoses to feed into and out of the water cooler then I’ll use those fittings.