mkov608
Active Member
With the riding season over for the majority of us, it’s time to do all the required post-season maintenance. Speaking from experience, proper post-season maintenance ensures an uneventful post-winter storage launch, reduced mechanical problems, and a more enjoyable riding season next year. Not too long ago, I came across a thread concerning jet pump bearing lubrication. One of the individuals recommended that for those of us who own skis with grease-filled pumps to cut the grease quantity in half and to fill up the remainder with oil. Instead of responding outright as to the error of that recommendation, I decided to do a little research and then report back to the group with information from the experts (professional engineers). The bottom line of my research is simple; follow your Sea-Doo service manual’s recommendations for type and quantity of lubrication, and be careful when following the advice of a non-credentialed individual who is telling you to “try this” or “try that”. After all, jet-pump parts are expensive!
Specifically, I found my information on the Timken and SKF bearing websites, with the additional support directly from an SKF engineer via their website. Special thanks go out to Joe McKnight, who is a mechanical engineer who works for BASF.
First, let’s discuss the qualities of oil verses grease.
Synthetic oil: Several characteristics make oil the best choice for jet pump bearings. The RPM of the jet pump bearing, oils inability to absorb water, and its ability to flush and cool the bearing make it the best choice.
Synthetic Grease: Grease also works in jet pumps based on the speed and load on the bearing, and its inability to absorb water, but it will not match oils heat wicking/cooling or flushing ability. The one thing grease has going for it is its tackiness/stickiness. If there is a seal failure (like I experience), grease will stay in the bearing and protect it for a longer period of time. My personal though here is that heat isn’t that big of a problem for jet pump bearings since the vanes in the pump serve as a type of radiator and there is a constant flow of water through the pump to keep it cool.
Second, let me cover what happens in a jet pump where someone takes it upon themselves to mix oil and grease. Depending on the type of oil and grease used, mixing the two has the potential to make very dangerous cocktail where the chemicals in the grease mix with those in the oil and they attack each other. This worst case scenario could spell disaster for the pump seals and the bearing.
The next thing that happens is that the oil will break down the grease “The oil will break down the grease in short order (Like adding too much water to cement) - greases normally have high EP (Extreme Pressure) ratings because they are in a base thickener. Regardless, it will change all the critical qualities for both the oil and grease.”
The last thing (another potential jet pump killer) is: “If there is too much oil (covers more than 30-50% of the bearing) - it will boil the bearing and destroy it because it can’t get rid of heat.”
Whatever you do, don’t believe me! Do your own research, especially when someone is advising you to deviate from your Sea-Doo service manual. Following the service procedures in your Sea-Doo or Clymer shop manual will yield years of trouble-free service.
Here are the links to the Timken and SKF sites:
http://www.timken.com/en-us/products/lubrication/Pages/faq.aspx
http://www.skf.com/us/products/lubrication-solutions/lubricants/index.html
Specifically, I found my information on the Timken and SKF bearing websites, with the additional support directly from an SKF engineer via their website. Special thanks go out to Joe McKnight, who is a mechanical engineer who works for BASF.
First, let’s discuss the qualities of oil verses grease.
Synthetic oil: Several characteristics make oil the best choice for jet pump bearings. The RPM of the jet pump bearing, oils inability to absorb water, and its ability to flush and cool the bearing make it the best choice.
Synthetic Grease: Grease also works in jet pumps based on the speed and load on the bearing, and its inability to absorb water, but it will not match oils heat wicking/cooling or flushing ability. The one thing grease has going for it is its tackiness/stickiness. If there is a seal failure (like I experience), grease will stay in the bearing and protect it for a longer period of time. My personal though here is that heat isn’t that big of a problem for jet pump bearings since the vanes in the pump serve as a type of radiator and there is a constant flow of water through the pump to keep it cool.
Second, let me cover what happens in a jet pump where someone takes it upon themselves to mix oil and grease. Depending on the type of oil and grease used, mixing the two has the potential to make very dangerous cocktail where the chemicals in the grease mix with those in the oil and they attack each other. This worst case scenario could spell disaster for the pump seals and the bearing.
The next thing that happens is that the oil will break down the grease “The oil will break down the grease in short order (Like adding too much water to cement) - greases normally have high EP (Extreme Pressure) ratings because they are in a base thickener. Regardless, it will change all the critical qualities for both the oil and grease.”
The last thing (another potential jet pump killer) is: “If there is too much oil (covers more than 30-50% of the bearing) - it will boil the bearing and destroy it because it can’t get rid of heat.”
Whatever you do, don’t believe me! Do your own research, especially when someone is advising you to deviate from your Sea-Doo service manual. Following the service procedures in your Sea-Doo or Clymer shop manual will yield years of trouble-free service.
Here are the links to the Timken and SKF sites:
http://www.timken.com/en-us/products/lubrication/Pages/faq.aspx
http://www.skf.com/us/products/lubrication-solutions/lubricants/index.html
