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Water Reversion 300XS Solved
Preface:
If you own a 300XS Outboard motor and are running twins or single in the triple digit realm you will have water reversion issues. What is water reversion? It occurs at high speed [typically 85+ MPH] when the head water from the motor is dumped out onto the wingplate. Upon exit at high speed the vacuum created by the air flow around the cowling creates a vacuum/capillary effect. Wherein, the water is drawn into the cowling intake.
If you boat in saltwater this can cause tremendous damage to your engine components. As saltwater is extremely caustic and will destroy expensive electrical components and related parts in no time at all. This will leave you constantly in contact with your Mercury warranty department and discussing wrangling over the cause and affect of your failures.
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Origin of Idea:
I spoke to one of our racers throttleman... Dan Lawrence in the current 2012 National Championship Outboard boat.... S-1 Doug Wright Duce Rods. He informed me the solution was to eliminate the head water near and above the wing plates and in turn it would cure the problem of water reversion. For me preserving the warranty status of new motors is paramount as this is a huge selling point for these engines. This kit also benefits Mercury as they would have far fewer warranty claims and the customer would be on the water longer with less headaches. Than if he did not have this on the motor. In the end it is a win/win solution for all involved.
Solution:
We researched several other people who alleged they had a cure for this problem, but none really addressed the origin of the problem. In addition, some of the solutions proposed were to cut, install or modify items which would relieve the vacuum created. This was not acceptable to me as it undoubtedly would void any warranty from Mercury. Not to mention I am not fond of cutting brand new cowlings up or making such drastic alterations. In addition, cutting into the cowling would also alter the air/fuel mixture [lean condition] and create a myriad of other problems. These proposed solutions were not acceptable to me and really in my opinon sacrificed areas including reliability and warranty compliance.
So I began testing in Galveston during the Texas Outlaw Challenge of our water reversion kit and after days of running including one day of over 188 miles in saltwater. We pulled the cowlings for inspection and found no water present underneath the cowlings. We even left the insulation in the cowlings to keep everything as close to factory as possible. Note: the cowling insulation acts like a giant sponge and if water were present it would immediately be noticed. The idea was working but we needed a clean custom look that was worthy of installation on the boat. This was the second phase of the solution.
We commissioned a part to be machined and installed in the water dump. We then had the wing plates CNC and chamfered to pass the hose dump through. I am happy to report this has cured all water reversion issues on our boat. The engines are untouched and factory stock in configuration. When the dump water is routed below the wing plate the water reversion is eliminated as there is no water in close proximity to the intake or rear portion of the cowling.
I have attached photos of what the kit looks like installed and I am very happy with it.
Note: Mercury Racing did provide two prototype test cowlings [300XS] to Mr. Wallner which he tested extensively including air/fuel mixtures. I spoke with him yesterday and he informed me the modified cowlings were too restrictive and suffocated the motors for lack of air.
We are now moving foward with the final phase of this kit... the final product material configuration. The current pieces are made of aluminum as they were test units. For the final finished product I will use 316 stainless which has a high corosion resistance over 304 stainless and should last a long time. I will have our machinist make a limited run of these units and thus I really need to know the quantity.
If you are interested in a set for your boat please contact me via PM or E-Mail. I can also have your wing plates CNC'd and chamfered if necessary (See photo below). In the alternative you can do them yourself it is not difficult. Once I know how many units to make I will provide you with a final cost. Obviously the more units we make the lower the cost and if you want us to CNC the holes in the wing plates it becomes more involved. As of right now I just want a determination of how many units to produce.
Let me know if there is any interest otherwise I will just make them for our boats.
KAP
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