Watercraft Journal regarding catch cans

[beaver6713]

I watch Kevin on YouTube a lot, seems like he knows his shit and is not afraid to say what he is thinking. I came across a video about oil catch cans. I just bought the RIVA engine breather upgrade kit for my 2023 SVHO. But Kevin mentioned that it needs to be tied back into the air intake in order to create a "suction" to make it vent properly, not to have it open to the inside of the ski with just a filter. Now I am confused.

[GreenHulk Jr]

You do not want to vent the crank case vapors back into the intake. Routing the vent hose to the intake would provide better suction BUT you are increasing the chances of detonation. All you are doing is introducing hot oil vapors back into the intake; not only is this poor for peak performance but it also reduces the octane rating(resistance to "knock"/detonation) of the fuel that you are using. You will be just fine venting to atmosphere with a filter.

[ptscon]

Unless you're venting to the outside of the hull, everything inside will get sucked back into the intake anyway.

To me you might as well have a vent hose close to the intake so it sucks it in directly to reduce smell in the storage compartment. You would have to vent to the outside if you really want to stop blowby gasses from making their way back into the motor.

[Team Bilford]

You could reintroduce the vented gases if you use a good oil separator rather than a simple catch can. The main purpose of the catch can on supercharged skis is to keep oil and distillates from coating the intercooler decreasing its thermal efficiency. It's not as much of an issue with the Yamaha engine as it is with the plasma coated Rotax motor in the Sea Doo. If you are venting into the engine compartment as the vast majority of cans do, certainly a large portion of the lightest vapors are pulled back into the induction system.

[GreenHulk Jr]

You could reintroduce the vented gases if you use a good oil separator rather than a simple catch can. The main purpose of the catch can on supercharged skis is to keep oil and distillates from coating the intercooler decreasing its thermal efficiency. It's not as much of an issue with the Yamaha engine as it is with the plasma coated Rotax motor in the Sea Doo. If you are venting into the engine compartment as the vast majority of cans do, certainly a large portion of the lightest vapors are pulled back into the induction system.

This would be the case for a Sea-Doo but not for a Yamaha. The SVHO has an oil separator from the factory and very rarely will oil come out of the breather hose like a Sea-Doo; Sea-Doo does not use an oil separator and vents directly off the cylinder head. This is why very few modified Yamaha's use a catch can instead of a filter on the end of the breather hose. I'd agree that a large portion of the vapors are pulled back in when venting into the engine compartment. If the hull is properly vented this won't be an issue but there are very few people that properly ventilate their hull.

[Gilberjj]

You do not want to vent the crank case vapors back into the intake. Routing the vent hose to the intake would provide better suction BUT you are increasing the chances of detonation. All you are doing is introducing hot oil vapors back into the intake; not only is this poor for peak performance but it also reduces the octane rating(resistance to "knock"/detonation) of the fuel that you are using. You will be just fine venting to atmosphere with a filter.

Sounds like a catch can is a solution in search of a problem...

[chris1200]

I have never seen any back to back testing results… GreenHulk Jr that would be a nice YouTube video for your channel , for now I am keeping mine connected to the intake

[beaver6713]

You do not want to vent the crank case vapors back into the intake. Routing the vent hose to the intake would provide better suction BUT you are increasing the chances of detonation. All you are doing is introducing hot oil vapors back into the intake; not only is this poor for peak performance but it also reduces the octane rating(resistance to "knock"/detonation) of the fuel that you are using. You will be just fine venting to atmosphere with a filter.

Kind of what I figured. I will install the breather and plug the intake part off. Thank you

[seabrook]

This would be the case for a Sea-Doo but not for a Yamaha. The SVHO has an oil separator from the factory and very rarely will oil come out of the breather hose like a Sea-Doo; Sea-Doo does not use an oil separator and vents directly off the cylinder head. This is why very few modified Yamaha's use a catch can instead of a filter on the end of the breather hose. I'd agree that a large portion of the vapors are pulled back in when venting into the engine compartment. If the hull is properly vented this won't be an issue but there are very few people that properly ventilate their hull.

wow idk this!!! i always wondered why catch cans were not mentioned on yamaha's