Loss of speed - 2011 SX210

[OrangeTJ]

Took the boat out for the second ride of the year yesterday and had the opportunity to let it eat for a bit. Odd thing, though - top speed was about 5 mph less than it was ehen I put it away last fall = 42 vs 47 mph on GPS. Conditions yesterday were about as good as they get for hitting max speed; 70 degrees, smooth water, bimini down, just me and my 4 year old on the boat. I put Stabil in the fuel when I put the boat up last fall and put in an additional half tank of fuel to get it all the way full before launching two weeks ago this year, so half new(ish) & gas half old gas. I'm seeing max RPM of just shy of 8K as opposed to just shy of 8.3K last fall. Could it just be the older fuel? The boat got new plugs last spring and engines are running smoothly. Not noticing any cavitation. One other thing is that when going to WOT from idle, it doesn't instantly go all the way to full revs but rather tops out at about 7.5K and then increases to 8K as speed climbs. That's new. Any thoughts?

 

[Cobra Jet Steering LLC]

That sounds like the issue, try adding some high octane fuel next time at the pump.

 

[octavio3311]

X2

 

[B_Mutter]

This is a little trick we have learned here at the store:

Check your W.O.T adjustments. Back in the engine compartment where your control cables attach to the device that turns it into an electric signal for the motors, make sure you are hitting the W.O.T stop. The cables might have stretched and you aren't getting full range. The adjustment is simple, just loosen the check nut and tighten up the other nut. I don't have a picture at the current moment but when you look at it you will understand. I'll see if i can't get a picture uploaded shortly

 

[OrangeTJ]

Thanks for the suggestions! It has been a while since I checked my WOT adjustment, though I'm familiar with the procedure. Will get some high octane/fresh fuel in it and check the adjustment when I go out this weekend.

 

[Glassman]

Hmmm, could be a fuel issue. Or plugs.

Have you checked the plugs? Take a look at them to see how they are burning.

If you are nearly full of fuel it will be hard to add more higher octane gas to make any noticeable difference but you might try some
Royal Purple 11757 Max-Boost Octane Booster and Stabilizer - 16 oz - one can treats up to 25 gallons.

The good thing about it is that it increases octane WITHOUT adding more ethanol. Typically you have a hard time finding fuel with no ethanol. (at least I do)
Some gas docks have ethanol free fuel because it would otherwise get loaded with water over time.
Ethanol is very hydroscopic (attracts and absorbs water) which may account for a degradation of your fuel when left to sit while in storage. It sucks moisture right out of the air.

Typically higher octane at the gas pump means a bit more ethanol added to the fuel when blended - but I'm not looking to start a fuel thread - please don't beat me up over this...I bruise easily.

All I know is that this stuff works - I add it to my turbo'd RZR and it loves it!

Good luck with your hunt to find that lost MPH!

 

[ToddW850]

This may not be your issue, but wanted to throw it out there if the other suggestions don't work. I've read others (at least 3) losing speed and didn't know why. Some reported 10 mph less. They got the bottom of the boat washed (some type of acid wash I believe) and it returned to full speed. Crazy sounding I know. Just repeating what I read. I believe they may have still been hitting their full R.P.M.'s though, not sure.