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Discussion Starter #1
Ok, this seems like a usual question but I think mine is a little different.

It's seems strange but for some reason from time to time, my FXHO will run like a scalded dog and sometimes it won't. We went to the lake this weekend and after I pulled it off the trailer I took out across the lake. I was able to only get it up to about 60 on the digital speedometer (I know that is not the actual speed but I'm using it as a reference). After about 30 min of playing on it, the ski all of the sudden changed its attitude and I was able to top it out at like 85 on the digital guage (very noticeable difference in speed!). That afternoon while playing on it, it stayed at that level and didn't seem to loose any power. I pulled it in the slip to go up to the house for a couple hours and when we came back down for an evening run, the ski was back to its subdued self again. I tried and tried but couldn't get it to really take off like it had been doing earlier. Does this make sense? I thought I had experienced this in the past (extreme power) but hadn't been able to really put my finger on it until this past weekend.

Is this a fouled plug issue possibly? Don't get me wrong, its still fast but just not to the level I know its capable of.

Any help would be very much appreciated!
 

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Fist off I'd say that your speed-o-meter is way off. No way an FXHO is going anywhere near 85. Top speed of the pre-2009 models is around 58-60. 2009 and later will get up to around 64.

Usually when a plug fouls, you will definitely see a performance decrease, but I've not heard of one causing a surge then decline. It almost sounds like the engine is leaning out. You might want to check and clean the fuel injectors.
 

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Discussion Starter #3
It's a 2006 with about 70 hours, is it time for plugs? If so what plugs are the best for it?

I did add some seafoam to the tank this past weekend so maybe that will help with the injectors. Is there an easy way to get them clean? Is there another additive that works better on these machines?
 

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The FXHOs are known plug eaters. 70 hours is not a record, but if you have never changed them, I'd consider it as an essential first step with any performance problem. Fouled spark plugs are THE most common cause for power loss on this model ski...........extremely common. Seems to happen faster if you have to do a lot of cold idling (like idling out of a no wake zone right after you start the ski). After the ski is warm, idling is no problem, but try to avoid it when the engine is cold.

Problem with the CR9EB plugs is that they are small and foul easily, and unlike other plugs it is really hard to look at one and tell if it is bad or not. Best bet is to always replace the plugs when you experience a power loss on this model ski as a first step. I think that you can also use an iridium plug (CR9EIX), but they are about 2X as expensive. I don't know for sure that they would provide less fouling problems, but I would suspect that they would. I've also heard of guys experimenting with other plugs, but I don't know how they would work.

When changing this plug be sure the plug well is clean of debris first. Be very careful not to over torque (7-9 ft./lbs) or you will snap one off (they are fragile).

Yamaha makes an additive called Ring Free Plus that they recommend for 2 and 4 stroke engines. I've been using it for a while on my boat outboard and it seems to work well. Just started using some in my ski, so I don't know how it will work there.
 
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